F. Hoffmann-La Roche AG, CH-4070 Basel, Switzerland Case: P37509 FLUORESCENT PROBES FOR MAGL Field of the Invention The present invention relates to organic compounds useful as fluorescent probes for monoacylglycerol lipase (MAGL). Background of the Invention Fluorescent imaging probes have emerged as high resolution tools to investigate localization, e.g. expression levels and protein distribution in health and disease, structure, dynamics and function of proteins in living cells (L. A. Stoddart, L. E. Kilpatrick, S. J. Briddon, S. J. Hill, Neuropharmacology 2015, 98, 48-57). Such probes can e.g. be applied in flow cytometry fluorescence-activated cell sorting (FACS) experiments or cellular trafficking studies using confocal live cell imaging. Furthermore, fluorescent imaging probes allow for real-time monitoring of ligand-receptor interactions and protein visualization with high spatiotemporal precision (A. J. Vernall, S. J. Hill, B. Kellam, Br. J. Pharmacol.2014, 171, 1073–1084; C. Iliopoulos-Tsoutsouvas, R. N. Kulkarni, A. Makriyannis, S. P. Nikas, Expert Opin. Drug Discov.2018, 13, 933–947). In addition, such probes offer the potential for generating equilibrium and kinetic binding data in a high-throughput fashion, without handling radioactive material using e.g. time-resolved fluorescence resonance energy transfer (TR-FRET). Fluorescent imaging probes can also be useful to support the translation of preclinical pharmacological animal data to clinics and can be applied for dose selection in humans. They can e.g. be used as markers of target engagement via the generation of ex vivo quantitative receptor binding data in whole blood. Depending on the respective application, a fluorescent imaging probe needs to match specific criteria, including affinity, selectivity and specificity for the respective target, favorable photophysical properties, and applicability across distinct techniques and cell types. CNE/14.08.2023 Summary of the Invention In a first aspect, the present invention provides a compound of formula (I) or (II) or a pharmaceutically acceptable salt thereof, wherein A, L, n, and R ¹ to R ³ are as defined herein. In a further aspect, the present invention provides processes for manufacturing said compounds of formula (I) or (II). In a further aspect, the present invention provides a compound of formula (I) or (II) as described herein, when manufactured according to the processes described herein. In a further aspect, the present invention provides the use of a compound of formula (II) described herein for the preparation of a fluorescent probe of formula (I) described herein. In a further aspect, the present invention provides a method of studying monoacylglycerol lipase (MAGL) occupancy, comprising contacting MAGL with a compound of formula (I) described herein. In a further aspect, the present invention provides a method of diagnostic imaging of monoacylglycerol lipase (MAGL) in a mammal, comprising contacting MAGL with a compound of formula (I) described herein. In a further aspect, the present invention provides a method of generating monoacylglycerol lipase (MAGL) equilibrium and kinetic binding data, comprising contacting MAGL with a compound of formula (I) described herein. Detailed Description of the Invention Definitions Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein, unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. The term "heteroaryl" refers to a mono- or multivalent, monocyclic, bicyclic or tricyclic, preferably bicyclic ring system having a total of 5 to 14 ring members, preferably, 5 to 12 ring members, and more preferably 5 to 10 ring members, wherein at least one ring in the system is aromatic, and at least one ring in the system contains one or more heteroatoms. Preferably, “heteroaryl” refers to a 5-10 membered heteroaryl comprising 1, 2, 3 or 4 heteroatoms independently selected from O, S and N. Most preferably, “heteroaryl” refers to a 5-10 membered heteroaryl comprising 1 to 2 heteroatoms independently selected from O, S and N. Some non-limiting examples of heteroaryl include spiro[cyclopropane-1,3'- indoline] (e.g., spiro[cyclopropane-1,3'-indoline]-1'-yl), 2-pyridyl, 3-pyridyl, 4-pyridyl, pyrazin-2-yl, pyrimidin-2-yl, pyrimidin-4-yl, pyrimidin-5-yl, pyrimidin-6-yl, indol-1-yl, 1H-indol-2-yl, 1H-indol-3-yl, 1H-indol-4-yl, 1H-indol-5-yl, 1H-indol-6-yl, 1H-indol-7-yl, 1,2-benzoxazol-3-yl, 1,2-benzoxazol-4-yl, 1,2-benzoxazol-5-yl, 1,2-benzoxazol-6-yl, 1,2- benzoxazol-7-yl, 1H-indazol-3-yl, 1H-indazol-4-yl, 1H-indazol-5-yl, 1H-indazol-6-yl, 1H- indazol-7-yl, pyrazol-1-yl, 1H-pyrazol-3-yl, 1H-pyrazol-4-yl, 1H-pyrazol-5-yl, pyrazolo[1,5-a]pyridine, 2H-pyrazolo[4,3-b]pyridine, [1,2,4]triazolo[1,5-a]pyridine, 1H- pyrrolo[2,3-b]pyridine, imidazol-1-yl, 1H-imidazol-2-yl, 1H-imidazol-4-yl, 1H-imidazol- 5-yl, oxazol-2-yl, oxazol-4-yl, oxazol-5-yl, 1,2,4-oxadiazolyl, 1,3,4-oxadiazolyl, thiazol-2- yl, thiazol-4-yl, thiazol-5-yl, pyridazin-3-yl, pyridazin-4-yl, 1,2,4-triazol-4-yl, 1,2,4- triazol-1-yl, 4H-1,2,4-triazol-3-yl, 4,5,6,7-tetrahydroindazol-2-yl, 6,7-dihydro-4H- pyrano[4,3-c]pyrazol-2-yl, thiazolyl, benzofurazan-4-yl, tetrazolyl, isoxazolyl, pyrrolyl, and morpholinyl. The term "aryl" refers to a monocyclic, bicyclic, or tricyclic carbocyclic ring system having a total of 6 to 10 ring members (“C6-C10-aryl”), wherein at least one ring in the system is aromatic. Some non-limiting examples of aryl include phenyl and 9H-fluorenyl (e.g.9H-fluoren-9-yl). A particularly preferred, yet non-limiting example of aryl is phenyl. The term “alkyl” refers to a mono- or multivalent, e.g., a mono- or bivalent, linear or branched saturated hydrocarbon group of 1 to 12 carbon atoms. In some preferred embodiments, the alkyl group contains 1 to 6 carbon atoms, e.g., 1, 2, 3, 4, 5, or 6 carbon atoms (“C1-C6-alkyl”). In other embodiments, the alkyl group contains 1 to 3 carbon atoms, e.g., 1, 2 or 3 carbon atoms. Some non-limiting examples of alkyl include methyl, ethyl, propyl, 2-propyl (isopropyl), n-butyl, iso-butyl, sec-butyl, tert-butyl, and 2,2- dimethylpropyl. A particularly preferred, yet non-limiting example of alkyl is methyl. The term “alkoxy” refers to an alkyl group, as previously defined, attached to the parent molecular moiety via an oxygen atom. Unless otherwise specified, the alkoxy group contains 1 to 12 carbon atoms. In some preferred embodiments, the alkoxy group contains 1 to 6 carbon atoms (“C1-C6-alkoxy”). In other embodiments, the alkoxy group contains 1 to 4 carbon atoms. In still other embodiments, the alkoxy group contains 1 to 3 carbon atoms. Some non-limiting examples of alkoxy groups include methoxy, ethoxy, n- propoxy, isopropoxy, n-butoxy, isobutoxy and tert-butoxy. A particularly preferred, yet non-limiting example of alkoxy is methoxy. The term “alkoxycarbonyl” refers to an alkoxy group, as previously defined, attached to the parent molecular moiety via a carbonyl group. In some preferred embodiments, the alkoxy moiety of the alkoxycarbonyl group contains 1 to 6 carbon atoms (“C1-C6- alkoxycarbonyl”). In other embodiments, the alkoxy group contains 1 to 4 carbon atoms. In still other embodiments, the alkoxy group contains 1 to 3 carbon atoms. Some non- limiting examples of alkoxycarbonyl groups include methoxycarbonyl, ethoxycarbonyl, n- propoxycarbonyl, isopropoxycarbonyl, n-butoxycarbonyl, isobutoxycarbonyl and tert- butoxycarbonyl. A particularly preferred, yet non-limiting example of alkoxy is tert- butoxycarbonyl. The term "pharmaceutically acceptable salt" refers to those salts which retain the biological effectiveness and properties of the free bases or free acids, which are not biologically or otherwise undesirable. The salts are formed with inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid and the like, in particular hydrochloric acid, and organic acids such as acetic acid, propionic acid, glycolic acid, pyruvic acid, oxalic acid, maleic acid, malonic acid, succinic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, salicylic acid, N-acetylcystein and the like. In addition, these salts may be prepared by addition of an inorganic base or an organic base to the free acid. Salts derived from an inorganic base include, but are not limited to, the sodium, potassium, lithium, ammonium, calcium, magnesium salts and the like. Salts derived from organic bases include, but are not limited to salts of primary, secondary, and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines and basic ion exchange resins, such as isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, ethanolamine, lysine, arginine, N- ethylpiperidine, piperidine, polyimine resins and the like. Particular pharmaceutically acceptable salts of compounds of formula (I) are hydrochloride salts. The compounds of formula (I) can contain several asymmetric centers and can be present in the form of optically pure enantiomers, mixtures of enantiomers such as, for example, racemates, optically pure diastereioisomers, mixtures of diastereoisomers, diastereoisomeric racemates or mixtures of diastereoisomeric racemates. According to the Cahn-Ingold-Prelog Convention, the asymmetric carbon atom can be of the "R" or "S" configuration. The abbreviation “MAGL” refers to the enzyme monoacylglycerol lipase. The terms “MAGL” and “monoacylglycerol lipase” are used herein interchangeably. Compounds of the Invention In a first aspect, the present invention provides a compound of formula (I) or (II) A A n (I) (II) or a pharmaceutically acceptable salt thereof, wherein: R ¹ is selected from: ; wherein a wavy line indicates the point of attachment of R ¹ to the remainder of formula (I) or (II); R ² is selected from:

, , , p p , , and ; wherein: a wavy line indicates the point of attachment of R ² to the remainder of formula (I); p is 1 or 2; is selected from hydrogen and methyl; W is selected from methyl, phenyl, , , , , , ; wherein Ar is C6-C10-aryl or 5- to 14-membered heteroaryl; is selected from O, S, Si(CH ₃ ) ₂ , and CH ₂ ; and is selected from OH, NH ₂ , N(CH ₃ ) ₂ , N(CD ₃ ) ₂ , and azetidin-1-yl; R ³ is selected from hydrogen, C1-C6-alkoxycarbonyl and C1-C6-alkoxycarbonyl- NH-C ₁ -C ₆ -alkyl-NH-C(O)–; (ii) X and L, taken together, form a group , wherein the wavy line indicates the point of attachment of L to the phenyl moiety within formula (I) or (II), and the two asterisks indicate the points of attachment of X to the respective neighbouring atoms within ring A; wherein a wavy line indicates the point of attachment of A to L; and an asterisk indicates the point of attachment of A to the carbonyl group of formula (I) or (II); and n is an integer selected from 1, 2, 3 and 4. In one embodiment, the present invention provides a compound of formula (I) or (II) as described herein or a pharmaceutically acceptable salt thereof, wherein: in Formula (I), R ¹ is selected from: , , , and ; wherein a wavy line indicates the point of attachment of R ¹ to the remainder of formula (I); in Formula (II), R ¹ is selected from: wherein a wavy line indicates the point of attachment of R ¹ to the remainder of formula (II); R ² is selected from:

, , , p p , , and ; wherein: a wavy line indicates the point of attachment of R ² to the remainder of formula (I); p is 1 or 2; V is selected from hydrogen and methyl; , Ar is C ₆ -C ₁₀ -aryl or 5- to 14-membered heteroaryl; X is selected from O, S, Si(CH3)2, and CH2; and Y is selected from OH, NH ₂ , N(CH ₃ ) ₂ , N(CD ₃ ) ₂ , and azetidin-1-yl; R ³ is selected from hydrogen, C1-C6-alkoxycarbonyl and C1-C6-alkoxycarbonyl- NH-C ₁ -C ₆ -alkyl-NH-C(O)–; A is: (ii) X and L, taken together, form a group , wherein the wavy line indicates the point of attachment of L to the phenyl moiety within formula (I) or (II), and the two asterisks indicate the points of attachment of X to the respective neighbouring atoms within ring A; wherein a wavy line indicates the point of attachment of A to L; and an asterisk indicates the point of attachment of A to the carbonyl group of formula (I) or (II); and n is an integer selected from 1, 2, 3 and 4. In one aspect, the present invention provides a compound of formula (I) or a pharmaceutically acceptable salt thereof, wherein R ¹ , R ² , A, L, and n are as defined herein. In one aspect, the present invention provides a compound of formula (II) or a pharmaceutically acceptable salt thereof, wherein R ¹ , R ³ , A, and L are as defined herein. In one embodiment, the present invention provides a compound of formula (I) or (II) as described herein, or a pharmaceutically acceptable salt thereof, wherein R ¹ is selected from: wherein a wavy line indicates the point of attachment of R ¹ to the remainder of formula (I). In one embodiment, the present invention provides a compound of formula (I) or (II) as described herein, or a pharmaceutically acceptable salt thereof, wherein R ¹ is ; wherein a wavy line indicates the point of attachment of R ¹ to the remainder of formula (I). In one embodiment, the present invention provides a compound of formula (I) or (II) as described herein, or a pharmaceutically acceptable salt thereof, wherein R ¹ is ; wherein a wavy line indicates the point of attachment of R ¹ to the remainder of formula (I). In one embodiment, the present invention provides a compound of formula (I) as described herein, or a pharmaceutically acceptable salt thereof, wherein A is: (i) X is CH; and L is selected from –CH2– and –CH2O–; or (ii) X and L, taken together, form a group , wherein the wavy line indicates the point of attachment of L to the phenyl moiety within formula (I), and the two asterisks indicate the points of attachment of X to the respective neighbouring atoms within ring A; wherein a wavy line indicates the point of attachment of A to L; and an asterisk indicates the point of attachment of A to the carbonyl group of formula (I). In one embodiment, the present invention provides a compound of formula (I) as described herein, or a pharmaceutically acceptable salt thereof, wherein A is: ; (i) X is CH and L is –CH2–; or (ii) X and L, taken together, form a group , wherein the wavy line indicates the point of attachment of L to the phenyl moiety within formula (I), and the two asterisks indicate the points of attachment of X to the respective neighbouring atoms within ring A; wherein a wavy line indicates the point of attachment of A to L; and an asterisk indicates the point of attachment of A to the carbonyl group of formula (I). In a preferred embodiment, the present invention provides a compound of formula (I) as described herein, or a pharmaceutically acceptable salt thereof, wherein A is: X is CH; wherein a wavy line indicates the point of attachment of A to L; and an asterisk indicates the point of attachment of A to the carbonyl group of formula (I). In a particularly preferred embodiment, the present invention provides a compound of formula (I) as described herein, or a pharmaceutically acceptable salt thereof, wherein A is wherein a wavy line indicates the point of attachment of A to L; and an asterisk indicates the point of attachment of A to the carbonyl group of formula (I). In a particularly preferred embodiment, the present invention provides a compound of formula (I) as described herein, or a pharmaceutically acceptable salt thereof, wherein A is and L is –CH ₂ –; wherein X is CH; a wavy line indicates the point of attachment of A to L; and an asterisk indicates the point of attachment of A to the carbonyl group of formula (I). In one embodiment, the present invention provides a compound of formula (I) as described herein, or a pharmaceutically acceptable salt thereof, wherein: R ² is selected from: , a wavy line indicates the point of attachment of R ² to the remainder of formula (I); p is 1; V is methyl; W is methyl X is selected from O and Si(CH ₃ ) ₂ ; and Y is N(CH ₃ ) ₂ ; and n is an integer selected from 1, 2, and 4. In a preferred embodiment, the present invention provides a compound of formula (I) as described herein, or a pharmaceutically acceptable salt thereof, wherein: R ² is selected from: , , , and p ; wherein: a wavy line indicates the point of attachment of R ² to the remainder of formula (I); p is 1; V is methyl; W is methyl X is selected from O and Si(CH3)2; and Y is N(CH3)2; and n is an integer selected from 1, 2, and 4. In a preferred embodiment, the present invention provides a compound of formula (I) as described herein, or a pharmaceutically acceptable salt thereof, wherein: R ² is selected from:

, , , and p ; wherein: a wavy line indicates the point of attachment of R ² to the remainder of formula (I); p is 1; V is methyl; W is methyl X is selected from O and Si(CH3)2; and Y is N(CH3)2; and n is an integer selected from 1 and 4. In a particularly preferred embodiment, the present invention provides a compound of formula (I) as described herein, or a pharmaceutically acceptable salt thereof, wherein: 2 R is ; wherein: the wavy line indicates the point of attachment of R ² to the remainder of formula (I); and n is an integer selected from 1 and 4. In a particularly preferred embodiment, the present invention provides a compound of formula (I) as described herein, or a pharmaceutically acceptable salt thereof, wherein: R ² is ; wherein: the wavy line indicates the point of attachment of R ² to the remainder of formula (I); V is methyl; W is methyl; and n is an integer selected from 1 and 4. In a particularly preferred embodiment, the present invention provides a compound of formula (I) as described herein, or a pharmaceutically acceptable salt thereof, wherein: R ² ; wherein: the wavy line indicates the point of attachment of R ² to the remainder of formula (I); X is selected from O and Si(CH ₃ ) ₂ ; Y is N(CH3)2; and n is an integer selected from 1 and 4. In a particularly preferred embodiment, the present invention provides a compound of formula (I) as described herein, or a pharmaceutically acceptable salt thereof, wherein: R ² wherein: the wavy line indicates the point of attachment of R ² to the remainder of formula (I); p is 1; and n is an integer selected from 1 and 4. In one embodiment, the present invention provides a compound of formula (II) as described herein, or a pharmaceutically acceptable salt thereof, wherein A is: (i) and L is selected from –OCH2–, –CH2OCH2–, and –O–; or (ii) and L is –CH2O–; wherein X is CH; wherein a wavy line indicates the point of attachment to L; and an asterisk indicates the point of attachment to the carbonyl group of formula (II). In one embodiment, the present invention provides a compound of formula (I) as described herein, wherein: R ¹ is selected from: ; wherein a wavy line indicates the point of attachment of R ¹ to the remainder of formula (I); R ² is selected from: , , , p , and ; wherein: a wavy line indicates the point of attachment of R ² to the remainder of formula (I); p is 1; V is methyl; W is methyl X is selected from O and Si(CH3)2; and Y is N(CH3)2; A is: (ii) X and L, taken together, form a group , wherein the wavy line indicates the point of attachment of L to the phenyl moiety within formula (I), and the two asterisks indicate the points of attachment of X to the respective neighbouring atoms within ring A; wherein a wavy line indicates the point of attachment to L; and an asterisk indicates the point of attachment to the carbonyl group of formula (I); and n is an integer selected from 1, 2, and 4. In a preferred embodiment, the present invention provides a compound of formula (I) as described herein, wherein: R ¹ is selected from: wherein a wavy line indicates the point of attachment of R ¹ to the remainder of formula (I); R ² is selected from: a wavy line indicates the point of attachment of R ² to the remainder of formula (I); p is 1; V is methyl; W is methyl X is selected from O and Si(CH3)2; and Y is N(CH3)2; A is: (ii) X and L, taken together, form a group , wherein the wavy line indicates the point of attachment of L to the phenyl moiety within formula (I), and the two asterisks indicate the points of attachment of X to the respective neighbouring atoms within ring A; wherein a wavy line indicates the point of attachment of A to L; and an asterisk indicates the point of attachment of A to the carbonyl group of formula (I); and n is an integer selected from 1, 2, and 4. In a particularly preferred embodiment, the present invention provides a compound of formula (I) as described herein, wherein: wherein a wavy line indicates the point of attachment of R ¹ to the remainder of formula (I); R ² is selected from: , , , and p ; wherein: a wavy line indicates the point of attachment of R ² to the remainder of formula (I); p is 1; V is methyl; W is methyl X is selected from O and Si(CH3)2; and Y is N(CH3)2; A is: X is CH; wherein a wavy line indicates the point of attachment of A to L; and an asterisk indicates the point of attachment of A to the carbonyl group of formula (I); and n is an integer selected from 1 and 4. In one embodiment, the present invention provides a compound of formula (I) or (II) as described herein, wherein the compound of formula (I) or (II) is selected from: benzyl (2-(2-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)methoxy)methyl)phenoxy)ethyl)carbamat e; benzyl (2-(2-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)oxy)methyl)phenoxy)ethyl)carbamate; benzyl (2-(2-(((2-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6-carbonyl)- 2-azaspiro[3.3]heptan-6-yl)oxy)methyl)phenoxy)ethyl)carbamat e; benzyl (2-(2-(((2-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6-carbonyl)- 2-azaspiro[3.5]nonan-7-yl)oxy)methyl)phenoxy)ethyl)carbamate ; benzyl (2-(3-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)methoxy)methyl)phenoxy)ethyl)carbamat e; benzyl (2-(3-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)oxy)methyl)phenoxy)ethyl)carbamate; benzyl (2-(3-(((2-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6-carbonyl)- 2-azaspiro[3.3]heptan-6-yl)oxy)methyl)phenoxy)ethyl)carbamat e; benzyl (3-(3-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)methoxy)methyl)phenoxy)propyl)carbama te; benzyl (6-(2-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)methoxy)methyl)phenoxy)hexyl)carbamat e; benzyl (2-(2-(((1-(6-oxo-7-oxa-2,5-diazaspiro[3.4]octane-2-carbonyl )azetidin-3- yl)methoxy)methyl)phenoxy)ethyl)carbamate; cyclohex-1-en-1-ylmethyl (2-(2-((2-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3- b][1,4]oxazine-6-carbonyl)-2-azaspiro[3.3]heptan-6- ylidene)methyl)phenoxy)ethyl)carbamate; benzyl (2-(3-((2-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxa zine-6-carbonyl)-2- azaspiro[3.3]heptan-6-ylidene)methyl)phenoxy)ethyl)carbamate ; benzyl (2-(2-((2-(6-oxo-7-oxa-2,5-diazaspiro[3.4]octane-2-carbonyl) -2- azaspiro[3.3]heptan-6-ylidene)methyl)phenoxy)ethyl)carbamate ; benzyl (2-(2-(((7-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6-carbonyl)- 7-azaspiro[3.5]nonan-2-yl)oxy)methyl)phenoxy)ethyl)carbamate ; benzyl (5-(2-((2-(6-oxo-7-oxa-2,5-diazaspiro[3.4]octane-2-carbonyl) -2- azaspiro[3.3]heptan-6-ylidene)methyl)phenoxy)pentyl)carbamat e; benzyl (2-(2-((((1R,5S)-3-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b ][1,4]oxazine-6- carbonyl)-3-azabicyclo[3.1.0]hexan-6-yl)methoxy)methyl)pheno xy)ethyl)carbamate; benzyl (R)-(2-(2-(((1-(3-(2-oxooxazolidin-4-yl)propanoyl)azetidin-3 - yl)methoxy)methyl)phenoxy)ethyl)carbamate; benzyl (2-(2-(((1-(3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carb onyl)azetidin-3- yl)methoxy)methyl)phenoxy)ethyl)carbamate; 2-(6-(2-(2-((7-nitro-1l2,3l2-benzo[c][1,2,5]oxadiazol-4-yl)a mino)ethoxy)benzyl)-2- azaspiro[3.3]heptane-2-carbonyl)-7-oxa-2,5-diazaspiro[3.4]oc tan-6-one; (4aR,8aS)-6-(3-(((2-(2-((7-nitrobenzo[c][1,2,5]oxadiazol-4- yl)amino)ethoxy)benzyl)oxy)methyl)azetidine-1-carbonyl)hexah ydro-2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one; 2-(3-(((2-(2-((7-nitro-1H-3l2-benzo[c][1,2,5]oxadiazol-4- yl)amino)ethoxy)benzyl)oxy)methyl)azetidine-1-carbonyl)-7-ox a-2,5- diazaspiro[3.4]octan-6-one; (4aR,8aS)-6-(3-(((2-(3-((7-nitrobenzo[c][1,2,5]oxadiazol-4- yl)amino)propoxy)benzyl)oxy)methyl)azetidine-1-carbonyl)hexa hydro-2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one; (4aR,8aS)-6-(3-(((2-((5-((7-nitro-1,3-dihydrobenzo[c][1,2,5] oxadiazol-4- yl)amino)pentyl)oxy)benzyl)oxy)methyl)azetidine-1-carbonyl)h exahydro-2H- pyrido[4,3-b][1,4]oxazin-3(4H)-one; (4aR,8aS)-6-(6-(2-(2-((7-nitrobenzo[c][1,2,5]oxadiazol-4-yl) amino)ethoxy)benzyl)-2- azaspiro[3.3]heptane-2-carbonyl)hexahydro-2H-pyrido[4,3-b][1 ,4]oxazin-3(4H)-one; (4aR,8aS)-6-(6-(3-(2-((7-nitro-1,3-dihydrobenzo[c][1,2,5]oxa diazol-4- yl)amino)ethoxy)benzyl)-2-azaspiro[3.3]heptane-2-carbonyl)he xahydro-2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one; 2-(7-(Dimethylamino)-3-(dimethyliminio)-5,5-dimethyl-3,5-dih ydrodibenzo[b,e]silin-10- yl)-4-((5-(2-((2-(6-oxo-7-oxa-2,5-diazaspiro[3.4]octane-2-ca rbonyl)-2- azaspiro[3.3]heptan-6-yl)methyl)phenoxy)pentyl)carbamoyl)ben zoate; 3,3-dimethyl-1-(6-oxo-6-((2-(2-((2-(6-oxo-7-oxa-2,5-diazaspi ro[3.4]octane-2-carbonyl)-2- azaspiro[3.3]heptan-6-yl)methyl)phenoxy)ethyl)amino)hexyl)-2 -((E)-3-((Z)-1,3,3- trimethylindolin-2-ylidene)prop-1-en-1-yl)-3H-indol-1-ium 2,2,2-trifluoroacetate; 3-(5,5-difluoro-7,9-dimethyl-5H-5l4,6l4-dipyrrolo[1,2-c:2',1 '-f][1,3,2]diazaborinin-3-yl)- N-(2-(2-((2-(6-oxo-7-oxa-2,5-diazaspiro[3.4]octane-2-carbony l)-2-azaspiro[3.3]heptan- 6-yl)methyl)phenoxy)ethyl)propanamide; 2,2,2-trifluoroacetic acid, 3,3-dimethyl-1-(6-oxo-6-((2-(2-(((1-((4aR,8aS)-3-oxooctahydr o- 2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidin-3- yl)methoxy)methyl)phenoxy)ethyl)amino)hexyl)-2-((E)-3-((Z)-1 ,3,3-trimethylindolin- 2-ylidene)prop-1-en-1-yl)-3H-indol-1-ium salt; 3,3-dimethyl-1-(6-oxo-6-((2-(2-((2-((4aR,8aS)-3-oxooctahydro -2H-pyrido[4,3- b][1,4]oxazine-6-carbonyl)-2-azaspiro[3.3]heptan-6- yl)methyl)phenoxy)ethyl)amino)hexyl)-2-((E)-3-((Z)-1,3,3-tri methylindolin-2- ylidene)prop-1-en-1-yl)-3H-indol-1-ium 2,2,2-trifluoroacetate; 3-(5,5-difluoro-7,9-dimethyl-5H-5l4,6l4-dipyrrolo[1,2-c:2',1 '-f][1,3,2]diazaborinin-3-yl)- N-(2-(2-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4] oxazine-6- carbonyl)azetidin-3-yl)methoxy)methyl)phenoxy)ethyl)propanam ide; 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-4-( (2-(2-(((1-((4aR,8aS)-3- oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidi n-3- yl)methoxy)methyl)phenoxy)ethyl)carbamoyl)benzoate and 2-(6-(dimethylamino)-3- (dimethyliminio)-3H-xanthen-9-yl)-5-((2-(2-(((1-((4aR,8aS)-3 -oxooctahydro-2H- pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidin-3- yl)methoxy)methyl)phenoxy)ethyl)carbamoyl)benzoate; 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-5-( (2-(2-(((1-((4aR,8aS)-3- oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidi n-3- yl)methoxy)methyl)phenoxy)ethyl)carbamoyl)benzoate; 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-4-( (3-(2-(((1-((4aR,8aS)-3- oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidi n-3- yl)methoxy)methyl)phenoxy)propyl)carbamoyl)benzoate and 2-(6-(dimethylamino)-3- (dimethyliminio)-3H-xanthen-9-yl)-5-((3-(2-(((1-((4aR,8aS)-3 -oxooctahydro-2H- pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidin-3- yl)methoxy)methyl)phenoxy)propyl)carbamoyl)benzoate; 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-5-( (3-(2-(((1-((4aR,8aS)-3- oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidi n-3- yl)methoxy)methyl)phenoxy)propyl)carbamoyl)benzoate; 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-4-( (5-(2-((2-(6-oxo-7-oxa- 2,5-diazaspiro[3.4]octane-2-carbonyl)-2-azaspiro[3.3]heptan- 6- yl)methyl)phenoxy)pentyl)carbamoyl)benzoate compound and 2-(6-(dimethylamino)-3- (dimethyliminio)-3H-xanthen-9-yl)-5-((5-(2-((2-(6-oxo-7-oxa- 2,5- diazaspiro[3.4]octane-2-carbonyl)-2-azaspiro[3.3]heptan-6- yl)methyl)phenoxy)pentyl)carbamoyl)benzoate; 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-5-( (5-(2-((2-(6-oxo-7-oxa- 2,5-diazaspiro[3.4]octane-2-carbonyl)-2-azaspiro[3.3]heptan- 6- yl)methyl)phenoxy)pentyl)carbamoyl)benzoate; 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-4-( (5-(2-(((1-((4aR,8aS)-3- oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidi n-3- yl)methoxy)methyl)phenoxy)pentyl)carbamoyl)benzoate and 2-(6-(dimethylamino)-3- (dimethyliminio)-3H-xanthen-9-yl)-5-((5-(2-(((1-((4aR,8aS)-3 -oxooctahydro-2H- pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidin-3- yl)methoxy)methyl)phenoxy)pentyl)carbamoyl)benzoate; ethyl 3-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine -6-carbonyl)azetidin- 3-yl)methoxy)benzoate; ethyl 3-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine -6-carbonyl)azetidin- 3-yl)oxy)benzoate; ethyl 2-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine -6-carbonyl)azetidin- 3-yl)methoxy)benzoate; tert-Butyl (2-(3-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxa zine-6- carbonyl)azetidin-3-yl)oxy)benzamido)ethyl)carbamate; tert-butyl (2-(2-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxa zine-6- carbonyl)azetidin-3-yl)methoxy)benzamido)ethyl)carbamate; (4aR,8aS)-6-(3-((benzyloxy)methyl)azetidine-1-carbonyl)hexah ydro-2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one; (4aR,8aS)-6-(6-(benzyloxy)-2-azaspiro[3.3]heptane-2-carbonyl )hexahydro-2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one; and (4aR,8aS)-6-(3-(phenoxymethyl)azetidine-1-carbonyl)hexahydro -2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one. In one embodiment, the present invention provides a compound of formula (I) as described herein, wherein the compound of formula (I) is selected from: benzyl (6-(2-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)methoxy)methyl)phenoxy)hexyl)carbamat e; benzyl (2-(2-((2-(6-oxo-7-oxa-2,5-diazaspiro[3.4]octane-2-carbonyl) -2- azaspiro[3.3]heptan-6-ylidene)methyl)phenoxy)ethyl)carbamate ; benzyl (5-(2-((2-(6-oxo-7-oxa-2,5-diazaspiro[3.4]octane-2-carbonyl) -2- azaspiro[3.3]heptan-6-ylidene)methyl)phenoxy)pentyl)carbamat e; benzyl (R)-(2-(2-(((1-(3-(2-oxooxazolidin-4-yl)propanoyl)azetidin-3 - yl)methoxy)methyl)phenoxy)ethyl)carbamate; benzyl (2-(2-(((1-(3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carb onyl)azetidin-3- yl)methoxy)methyl)phenoxy)ethyl)carbamate; 2-(6-(2-(2-((7-nitro-1l2,3l2-benzo[c][1,2,5]oxadiazol-4-yl)a mino)ethoxy)benzyl)-2- azaspiro[3.3]heptane-2-carbonyl)-7-oxa-2,5-diazaspiro[3.4]oc tan-6-one; (4aR,8aS)-6-(3-(((2-(2-((7-nitrobenzo[c][1,2,5]oxadiazol-4- yl)amino)ethoxy)benzyl)oxy)methyl)azetidine-1-carbonyl)hexah ydro-2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one; 2-(3-(((2-(2-((7-nitro-1H-3l2-benzo[c][1,2,5]oxadiazol-4- yl)amino)ethoxy)benzyl)oxy)methyl)azetidine-1-carbonyl)-7-ox a-2,5- diazaspiro[3.4]octan-6-one; (4aR,8aS)-6-(3-(((2-(3-((7-nitrobenzo[c][1,2,5]oxadiazol-4- yl)amino)propoxy)benzyl)oxy)methyl)azetidine-1-carbonyl)hexa hydro-2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one; (4aR,8aS)-6-(3-(((2-((5-((7-nitro-1,3-dihydrobenzo[c][1,2,5] oxadiazol-4- yl)amino)pentyl)oxy)benzyl)oxy)methyl)azetidine-1-carbonyl)h exahydro-2H- pyrido[4,3-b][1,4]oxazin-3(4H)-one; (4aR,8aS)-6-(6-(2-(2-((7-nitrobenzo[c][1,2,5]oxadiazol-4-yl) amino)ethoxy)benzyl)-2- azaspiro[3.3]heptane-2-carbonyl)hexahydro-2H-pyrido[4,3-b][1 ,4]oxazin-3(4H)-one; (4aR,8aS)-6-(6-(3-(2-((7-nitro-1,3-dihydrobenzo[c][1,2,5]oxa diazol-4- yl)amino)ethoxy)benzyl)-2-azaspiro[3.3]heptane-2-carbonyl)he xahydro-2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one; 2-(7-(Dimethylamino)-3-(dimethyliminio)-5,5-dimethyl-3,5-dih ydrodibenzo[b,e]silin-10- yl)-4-((5-(2-((2-(6-oxo-7-oxa-2,5-diazaspiro[3.4]octane-2-ca rbonyl)-2- azaspiro[3.3]heptan-6-yl)methyl)phenoxy)pentyl)carbamoyl)ben zoate; 3,3-dimethyl-1-(6-oxo-6-((2-(2-((2-(6-oxo-7-oxa-2,5-diazaspi ro[3.4]octane-2-carbonyl)-2- azaspiro[3.3]heptan-6-yl)methyl)phenoxy)ethyl)amino)hexyl)-2 -((E)-3-((Z)-1,3,3- trimethylindolin-2-ylidene)prop-1-en-1-yl)-3H-indol-1-ium 2,2,2-trifluoroacetate; 3-(5,5-difluoro-7,9-dimethyl-5H-5l4,6l4-dipyrrolo[1,2-c:2',1 '-f][1,3,2]diazaborinin-3-yl)- N-(2-(2-((2-(6-oxo-7-oxa-2,5-diazaspiro[3.4]octane-2-carbony l)-2-azaspiro[3.3]heptan- 6-yl)methyl)phenoxy)ethyl)propanamide; 2,2,2-trifluoroacetic acid, 3,3-dimethyl-1-(6-oxo-6-((2-(2-(((1-((4aR,8aS)-3-oxooctahydr o- 2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidin-3- yl)methoxy)methyl)phenoxy)ethyl)amino)hexyl)-2-((E)-3-((Z)-1 ,3,3-trimethylindolin- 2-ylidene)prop-1-en-1-yl)-3H-indol-1-ium salt; 3,3-dimethyl-1-(6-oxo-6-((2-(2-((2-((4aR,8aS)-3-oxooctahydro -2H-pyrido[4,3- b][1,4]oxazine-6-carbonyl)-2-azaspiro[3.3]heptan-6- yl)methyl)phenoxy)ethyl)amino)hexyl)-2-((E)-3-((Z)-1,3,3-tri methylindolin-2- ylidene)prop-1-en-1-yl)-3H-indol-1-ium 2,2,2-trifluoroacetate; 3-(5,5-difluoro-7,9-dimethyl-5H-5l4,6l4-dipyrrolo[1,2-c:2',1 '-f][1,3,2]diazaborinin-3-yl)- N-(2-(2-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4] oxazine-6- carbonyl)azetidin-3-yl)methoxy)methyl)phenoxy)ethyl)propanam ide; 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-4-( (2-(2-(((1-((4aR,8aS)-3- oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidi n-3- yl)methoxy)methyl)phenoxy)ethyl)carbamoyl)benzoate and 2-(6-(dimethylamino)-3- (dimethyliminio)-3H-xanthen-9-yl)-5-((2-(2-(((1-((4aR,8aS)-3 -oxooctahydro-2H- pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidin-3- yl)methoxy)methyl)phenoxy)ethyl)carbamoyl)benzoate; 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-5-( (2-(2-(((1-((4aR,8aS)-3- oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidi n-3- yl)methoxy)methyl)phenoxy)ethyl)carbamoyl)benzoate; 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-4-( (3-(2-(((1-((4aR,8aS)-3- oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidi n-3- yl)methoxy)methyl)phenoxy)propyl)carbamoyl)benzoate and 2-(6-(dimethylamino)-3- (dimethyliminio)-3H-xanthen-9-yl)-5-((3-(2-(((1-((4aR,8aS)-3 -oxooctahydro-2H- pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidin-3- yl)methoxy)methyl)phenoxy)propyl)carbamoyl)benzoate; 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-5-( (3-(2-(((1-((4aR,8aS)-3- oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidi n-3- yl)methoxy)methyl)phenoxy)propyl)carbamoyl)benzoate; 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-4-( (5-(2-((2-(6-oxo-7-oxa- 2,5-diazaspiro[3.4]octane-2-carbonyl)-2-azaspiro[3.3]heptan- 6- yl)methyl)phenoxy)pentyl)carbamoyl)benzoate compound and 2-(6-(dimethylamino)-3- (dimethyliminio)-3H-xanthen-9-yl)-5-((5-(2-((2-(6-oxo-7-oxa- 2,5- diazaspiro[3.4]octane-2-carbonyl)-2-azaspiro[3.3]heptan-6- yl)methyl)phenoxy)pentyl)carbamoyl)benzoate; 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-5-( (5-(2-((2-(6-oxo-7-oxa- 2,5-diazaspiro[3.4]octane-2-carbonyl)-2-azaspiro[3.3]heptan- 6- yl)methyl)phenoxy)pentyl)carbamoyl)benzoate; and 2-(6-(dimethylamino)-3-(dimethyliminio)-3H-xanthen-9-yl)-4-( (5-(2-(((1-((4aR,8aS)-3- oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidi n-3- yl)methoxy)methyl)phenoxy)pentyl)carbamoyl)benzoate and 2-(6-(dimethylamino)-3- (dimethyliminio)-3H-xanthen-9-yl)-5-((5-(2-(((1-((4aR,8aS)-3 -oxooctahydro-2H- pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidin-3- yl)methoxy)methyl)phenoxy)pentyl)carbamoyl)benzoate. In one embodiment, the present invention provides a compound of formula (II) as described herein, wherein the compound of formula (II) is selected from: benzyl (2-(2-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)methoxy)methyl)phenoxy)ethyl)carbamat e; benzyl (2-(2-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)oxy)methyl)phenoxy)ethyl)carbamate; benzyl (2-(2-(((2-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6-carbonyl)- 2-azaspiro[3.3]heptan-6-yl)oxy)methyl)phenoxy)ethyl)carbamat e; benzyl (2-(2-(((2-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6-carbonyl)- 2-azaspiro[3.5]nonan-7-yl)oxy)methyl)phenoxy)ethyl)carbamate ; benzyl (2-(3-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)methoxy)methyl)phenoxy)ethyl)carbamat e; benzyl (2-(3-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)oxy)methyl)phenoxy)ethyl)carbamate; benzyl (2-(3-(((2-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6-carbonyl)- 2-azaspiro[3.3]heptan-6-yl)oxy)methyl)phenoxy)ethyl)carbamat e; benzyl (3-(3-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)methoxy)methyl)phenoxy)propyl)carbama te; benzyl (2-(2-(((1-(6-oxo-7-oxa-2,5-diazaspiro[3.4]octane-2-carbonyl )azetidin-3- yl)methoxy)methyl)phenoxy)ethyl)carbamate; cyclohex-1-en-1-ylmethyl (2-(2-((2-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3- b][1,4]oxazine-6-carbonyl)-2-azaspiro[3.3]heptan-6- ylidene)methyl)phenoxy)ethyl)carbamate; benzyl (2-(3-((2-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxa zine-6-carbonyl)-2- azaspiro[3.3]heptan-6-ylidene)methyl)phenoxy)ethyl)carbamate ; benzyl (2-(2-(((7-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6-carbonyl)- 7-azaspiro[3.5]nonan-2-yl)oxy)methyl)phenoxy)ethyl)carbamate ; benzyl (2-(2-((((1R,5S)-3-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b ][1,4]oxazine-6- carbonyl)-3-azabicyclo[3.1.0]hexan-6-yl)methoxy)methyl)pheno xy)ethyl)carbamate; ethyl 3-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine -6-carbonyl)azetidin- 3-yl)methoxy)benzoate; ethyl 3-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine -6-carbonyl)azetidin- 3-yl)oxy)benzoate; ethyl 2-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine -6-carbonyl)azetidin- 3-yl)methoxy)benzoate; tert-Butyl (2-(3-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxa zine-6- carbonyl)azetidin-3-yl)oxy)benzamido)ethyl)carbamate; tert-butyl (2-(2-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxa zine-6- carbonyl)azetidin-3-yl)methoxy)benzamido)ethyl)carbamate; (4aR,8aS)-6-(3-((benzyloxy)methyl)azetidine-1-carbonyl)hexah ydro-2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one; (4aR,8aS)-6-(6-(benzyloxy)-2-azaspiro[3.3]heptane-2-carbonyl )hexahydro-2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one; and (4aR,8aS)-6-(3-(phenoxymethyl)azetidine-1-carbonyl)hexahydro -2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one. In a particular embodiment, the present invention provides pharmaceutically acceptable salts of the compounds according to formula (I) as described herein. In a further particular embodiment, the present invention provides compounds according to formula (I) as described herein as free bases. Processes of Manufacturing The preparation of compounds of formula (I) or (II) of the present invention may be carried out in sequential or convergent synthetic routes. Syntheses of the invention are shown in the following general schemes. The skills required for carrying out the reaction and purification of the resulting products are known to those persons skilled in the art. The substituents and indices used in the following description of the processes have the significance given herein, unless indicated to the contrary. If one of the starting materials, intermediates or compounds of formula (I) or (II) contain one or more functional groups which are not stable or are reactive under the reaction conditions of one or more reaction steps, appropriate protective groups (as described e.g., in “Protective Groups in Organic Chemistry” by T. W. Greene and P. G. M. Wutts, 5th Ed., 2014, John Wiley & Sons, N.Y.) can be introduced before the critical step applying methods well known in the art. Such protective groups can be removed at a later stage of the synthesis using standard methods described in the literature. If starting materials or intermediates contain stereogenic centers, compounds of formula (I) or (II) can be obtained as mixtures of diastereomers or enantiomers, which can be separated by methods well known in the art e.g., chiral HPLC, chiral SFC or chiral crystallization. Racemic compounds can e.g., be separated into their antipodes via diastereomeric salts by crystallization with optically pure acids or by separation of the antipodes by specific chromatographic methods using either a chiral adsorbent or a chiral eluent. It is equally possible to separate starting materials and intermediates containing stereogenic centers to afford diastereomerically/enantiomerically enriched starting materials and intermediates. Using such diastereomerically/enantiomerically enriched starting materials and intermediates in the synthesis of compounds of formula (I) or (II) will typically lead to the respective diastereomerically/enantiomerically enriched compounds of formula (I) or (II). A person skilled in the art will acknowledge that in the synthesis of compounds of formula (I) or (II) - insofar not desired otherwise - an “orthogonal protection group strategy” will be applied, allowing the cleavage of several protective groups one at a time each without affecting other protective groups in the molecule. The principle of orthogonal protection is well known in the art and has also been described in literature (e.g. Barany and R. B. Merrifield, J. Am. Chem. Soc.1977, 99, 7363; H. Waldmann et al., Angew. Chem. Int. Ed. Engl.1996, 35, 2056). A person skilled in the art will acknowledge that the sequence of reactions may be varied depending on reactivity and nature of the intermediates. In more detail, the compounds of formula (I) or (II) can be manufactured by the methods given below, by the methods given in the examples or by analogous methods. Appropriate reaction conditions for the individual reaction steps are known to a person skilled in the art. Also, for reaction conditions described in literature affecting the described reactions see for example: Comprehensive Organic Transformations: A Guide to Functional Group Preparations, 2nd Edition, Richard C. Larock. John Wiley & Sons, New York, NY.1999). It was found convenient to carry out the reactions in the presence or absence of a solvent. There is no particular restriction on the nature of the solvent to be employed, provided that it has no adverse effect on the reaction or the reagents involved and that it can dissolve the reagents, at least to some extent. The described reactions can take place over a wide range of temperatures, and the precise reaction temperature is not critical to the invention. It is convenient to carry out the described reactions in a temperature range between -78 °C to reflux. The time required for the reaction may also vary widely, depending on many factors, notably the reaction temperature and the nature of the reagents. However, a period of from 0.5 hours to several days will usually suffice to yield the described intermediates and compounds. The reaction sequence is not limited to the one displayed in the schemes, however, depending on the starting materials and their respective reactivity, the sequence of reaction steps can be freely altered. If starting materials or intermediates are not commercially available or their synthesis not described in literature, they can be prepared in analogy to existing procedures for close analogues or as outlined in the experimental section. The following abbreviations are used in the present text: AcOH = acetic acid, ACN = acetonitrile , Boc = tert-butyloxycarbonyl, CAS RN = chemical abstracts registration number, Cbz = benzyloxycarbonyl, Cs2CO3 = cesium carbonate, CO = carbon monoxide, DMAP = 4-dimethylaminopyridine, DMF = N,N-dimethylformamide, DMP = Dess-Martin periodinane, DIBAL-H = Diisobutylaluminium hydride, DIPEA = N,N-diisopropylethylamine, dppf = 1,1 bis(diphenyl phosphino)ferrocene, EDC.HCl = N- (3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride, ESI = electrospray ionization, EtOAc = ethyl acetate, EtOH = ethanol, h = hour(s), FA = formic acid, H ₂ O = water, H2SO4 = sulfuric acid, Hal = halogen, HATU = 1-[bis(dimethylamino)methylene]- 1H-1,2,3-triazolo[4,5-b]pyridinium-3-oxide hexafluorophosphate, HBTU = O- benzotriazole-N,N,N’,N’-tetramethyl-uronium-hexafluoro-p hosphate, HCl = hydrogen chloride, HOBt = 1-hydroxy-1H-benzotriazole; HPLC = high performance liquid chromatography, , , K2CO3 = potassium carbonate, KHCO3 = potassium bicarbonate, KI = potassium iodide, KOH = potassium hydroxide, K ₃ PO ₄ = potassium phosphate tribasic, KOtBu = potassium tert-butoxide, LiAlH ₄ or LAH = lithium aluminium hydride, LiHMDS = lithium bis(trimethylsilyl)amide, LiOH = lithium hydroxide, LiTMP = lithium tetramehtyl-piperidine MgSO ₄ = magnesium sulfate, min = minute(s), mL = milliliter, MPLC = medium pressure liquid chromatography, MS = mass spectrum, Ms = mesyl, NaH = sodium hydride, NaHCO3 = sodium hydrogen carbonate, , NaOH = sodium hydroxide, Na2CO3 = sodium carbonate, Na2SO4 = sodium sulfate, Na2S2O3 = sodium thiosulfate, NBS = N-bromosuccinimide, nBuLi = n-butyllithium, NEt ₃ = triethylamine (TEA), NH ₄ Cl = ammonium chloride, , NMP = N-methyl-2-pyrrolidone, OAc = Acetoxy, T3P = propylphosphonic anhydride, , , PG = protective group, Pd-C = palladium on activated carbon, Pd(dppf)Cl ₂ = 1,1'-bis(diphenylphosphino)ferrocene-palladium(II)dichloride , Pd2(dba)3 = tris(dibenzylideneacetone)dipalladium(0), Pd(OAc)2 = palladium(II) acetate, Pd(OH)2 = palladium hydroxide, Pd(PPh3)4 = tetrakis(triphenylphosphine)palladium(0), PTSA = p-toluenesulfonic acid, Ts, tosyl, R = any group, r.t. = room temperature, SFC = Supercritical Fluid Chromatography, TBAI = tetra butyl ammonium iodine, TEA = triethylamine, TFA = trifluroacetic acid, THF = tetrahydrofuran, TMEDA = N,N,N',N'- tetramethylethylenediamine, ,. Compounds of formula I wherein A, L, n, R ¹ , and R ² are as described herein can be synthesized in analogy to literature procedures and/or as depicted for example in Scheme 1. Scheme 1 Accordingly, amines derivatives 1 carry a suitable nitrogen protecting group “PG” at the end of the alkane chain, such as benzyloxycarbonyl (Cbz) carbamate, and an orthogonal nitrogen protecting group “PG ¹ ” at the cyclic amine, such as a tert-butyloxycarbonyl (Boc) carbamate. Removal of the protective group PG ¹ intermediates 1, applying methods known in the art (e.g., a Boc group using TFA in DCM at temperatures between 0 °C and room temperature, a Cbz group using hydrogen in the presence of a suitable catalyst such as Pd or Pd(OH)2 on charcoal in a suitable solvent such as MeOH, EtOH, EtOAc or mixtures thereof and as described for example in “Protective Groups in Organic Chemistry” by T.W. Greene and P.G.M. Wuts, 4th Ed., 2006, Wiley N.Y.), followed by reaction of the obtained free amine with compounds of the type 2a (R ¹ moieties that contain an N at the point of attachment to the remainder of formula I) in the presence of a urea forming reagent such as bis(trichloromethyl) carbonate using a suitable base and solvent such as, e.g. sodium bicarbonate in DCM, to furnish compounds 3, including compunds of the formula Ia (step a1). Further urea forming reagents include but are not limited to phosgene, trichloromethyl chloroformate, (4-nitrophenyl)carbonate or 1,1’-carbonyldiimidazole. Reactions of this type and the use of these reagents are widely described in literature (e.g. G. Sartori et al., Green Chemistry 2000, 2, 140). A person skilled in the art will acknowledge that the order of the addition of the reagents can be important in this type of reactions due to the reactivity and stability of the intermediary formed carbamoyl chlorides, as well as for avoiding formation of undesired symmetrical urea by-products. Alternatively, R ¹ moieties that contain a C at the point of attachment to the remainder of formula I are introduced as carboxyl acids that are coupled with intermediate amines obtained from following PG ¹ removal on 1, to form the respective amides, including compounds of the formula Ia (step a2). Amide couplings of this type can be accomplished by using one of the well-known coupling reagents such as DCC, HATU, EDCI, HOBt, TBTU, T3P, etc. and a base like Huenig’s base, triethylamine or DMAP in a suitable solvent like N,N-dimethylformamide, DMA, DCM or 1-4-dioxane, preferably between 0 °C and room temperature. Removal of the protective group in intermediates 3, applying methods known in the art (e.g., a Boc group using TFA in DCM at temperatures between 0 °C and room temperature, a Cbz group using hydrogen in the presence of a suitable catalyst such as Pd or Pd(OH)2 on charcoal in a suitable solvent such as MeOH, EtOH, EtOAc or mixtures thereof and as described for example in “Protective Groups in Organic Chemistry” by T.W. Greene and P.G.M. Wuts, 4th Ed., 2006, Wiley N.Y.), furnishes intermediates 4 (step b). Reaction of amines 4 with a fluorescent label containing a carboxylic acid moiety gives compounds of formula Ib (R ² = fluorescent label) (step c). Amide couplings of this type can be accomplished by using one of the well-known coupling reagents such as, DCC, HATU, EDCI, HOBt, TBTU, T3P, etc. and a base like Huenig’s base, triethyl amine or DMAP in a suitable solvent solvent like N,N-dimethylformamide, DMA, DCM or dioxane, preferably between 0 °C and room temperature. Alternatively, a fluorescent label containing an N- hydroxisuccinimide (NHS) activated ester can be reacted with 4 to afford compounds of the formula Ib in the presence of a suitable base, such as N,N-diisopropylethylamine (DIPEA), 2,6-lutidine, etc. in a suitable solvent such as DCM, THF, ACN, DMF, or dioxane, preferably between 0 °C and room temperature. To form final molecules Ib carrying a nitrobenzofurazan dye, amines 4 can be reacted in a nucleophic aromatic substitution with 4-chloro-7-nitrobenz-2-oxa-1,3-diazole (CAS RN 10199-89-0) or 4-fluoro-7-nitrobenz-2- oxa-1,3-diazole (CAS RN 29270-56-2), e.g. in the presence of a base such as triethylamine in a solvent as MeOH, preferably between 0 °C and room temperature (step c). Optionally, amine derivatives 1 in which “PG” is a fluorescent label can be converted directly to compounds of formula Ib according to step a. Protected amines 1 and their amine 2a or carboxylic acid 2b counterparts are either commercially available or can be prepared according to literature methods or as depicted below. Intermediates of type 1, such as intermediates 1a and 1b, can be prepared by a variety of conditions, which may be exemplified by the general synthetic procedure outlined in Scheme 2. Scheme 2 Intermediates 5, 6 and 11 are either commercially available or can be prepared according to literature methods. The functional hydroxyl group in 5 and 11 can be utilized to attach alkane chain derivatives of the type 6, where “LG” is a suitable leaving group such as, but not limited to, methanesulfonic ester (OMs), p-toluensulfonic ester (OTs), bromine, iodide, via nucleophilic substitution (S _N ) reactions in the presence of a suitable base (e.g. Cs ₂ CO ₃ , K2CO3), in a suitable solvent (e.g. DMF) preferably at temperatures between room temperature and 80 °C, to yield compounds 7 and 12, respectively (step d). Intermediates of the type 7 and 12 can also be obtained by other etherification reactions according to literature methods, or e.g. under Mitsunobu conditions with PPh3 and diethyl azodicarboxylate. Benzoic esters of type 7 can be transformed to their corresponding benzylic alcohols 8 by treatment with a suitable reducing agent, such as LiAlH ₄ , LiBH ₄ , diisobutylaluminium hydride (DIBAL-H), in a suitable solvent such as toluene, preferably at temperatures between -78° and 0° C (step e). Benzyl alcohols 8 can be converted into their benzyl bromide analogues 9 by reactions described in literature, such as Appel reaction with CBr4 and PPh3 or using PBr3, in a suitable solvent such as DCM, preferably at temperatures between 0 and 25 °C (step f). Molecules of the type 1a can be obtained by reacting benzyl bromides 9 with alcohols 10 in nucleophilic substitution reaction in presence of a suitable base, such as KOtBu, in a suitable solvent, such as THF, preferably at temperature between room temperature and 80 °C (step g). A person skilled in the art will acknowledge that other etherification methods describe in literature, as well as the use of analogues of bromine 9 that bear other suitable leaving groups instead of the bromine (e.g. I, OMs, OTs) can be used to produce 1a. Boronic acids, esters and their derivatives are known as versatile building blocks for transition metal mediated cross-coupling reactions. Intermediates of the type 1b can be readily accessed via cross-coupling reactions with suitable building blocks, such as vinyl boronic esters 13, in the presence of a suitable base such as K2CO3, a suitable water- containing solvent mixture such as water/dioxane, with a transition metal catalyst such as, but not limited to, Pd(dppf)Cl2, preferably at temperatures between 25 and 100 °C (step h). Alternatively, hydrolysis of vinyl boronates 13 by methods known to those skilled in the art, such as treatment with ammonium acetate buffered water/acetone mixtures and sodium periodate, can be conducted as an individual step, and subsequent (step h) can be conducted in absence of water. Vinyl boronic esters 13 are either commercially available or can be prepared according to literature methods or as depicted below. Vinyl boronates 13 (e.g. vinyl boronic acid pinacol ester) can be readily obtained as described in the literature (Kovalenko et al. , The Boron- Wittig Olefination of Aldehydes and Ketones with Bis[(pinacolato)boryl]methane: an Extended Reaction Scope. Eur J. Org. Chem., 2019: 5264-5635), for instance by treatment of ketones 14 with bis((pinacolato)boryl)methane (CAS RN 78782-17-9), in presence of a suitable base, such as Lithium tetramethyl piperindine (LiTMP). The general synthetic method is depicted in Scheme 3 (step i). Scheme 3 Compounds of formula II wherein A, L, R ¹ , and R ³ are as described herein can be synthesized in analogy to literature procedures and/or as depicted for example in Scheme 4. Scheme 4 Amines of the type 15, bearing a protecting group “PG ¹ ” such as those described for intermediates 1, and a leaving group “LG” as those described for intermediate 6 are either commercially available on can be readily accessed in one step from alcohol derivatives 10 by methods widely described in literature (e.g. by reaction with p-toluensulfonic acid chloride in presence of DMAP and TEA, or Comprehensive Organic Transformations: A Guide to Functional Group Preparations, 2nd Edition, Richard C. Larock. John Wiley & Sons, New York, NY.1999, step j). Phenol ester derivatives 16 can be reacted via nucleophilic substitution with intermediates 15 to afford ether intermediates 17, in analogy to the methods described for the transformation of 5 to 7 in scheme 2 (step d). Compounds of the type IIa can be obtained from 17 in analogy to the transformation of 1 to 3 in scheme 1 (step a). Compounds with the formula IIb can be obtained from reaction of IIa with amines 18 under amide coupling conditions, eg. by using one of the well-known coupling reagents such as, DCC, HATU, EDCI, HOBt, TBTU, T3P, etc. and a base like Huenig’s base, triethyl amine or DMAP in a suitable solvent solvent like N,N-dimethylformamide, DMA, DCM or dioxane, preferably at room temperature (step k). Treating benzyl bromide 19 with alcohols of the type 10 (see above) under nucleophilic substitution conditions, in the presence of a suitable base, such as sodium hydride (NaH) and a suitable solvent such as DMF/DCM mixture, preferably at temperatures between 0 and 25 °C affords ether intermediates 20 (step l). Compounds with the formula IIc, where R ³ = H to the remainder of formula II, are readily accessed from 20, in analogy to that described for the transformation of 1 to 3 in scheme 1 (step a). In one aspect, the present invention provides a process of manufacturing the compounds of formula (I) as described herein, comprising reacting an amine 4, wherein A, L, R ¹ , and n are as defined herein, with: (a) a fluorescent label containing a carboxylic acid moiety in the presence of a coupling reagent and a base; or (b) a fluorescent label containing an N-hydroxisuccinimide (NHS) activated ester in the presence of a base; or (c) 4-chloro-7-nitrobenz-2-oxa-1,3-diazole or 4-fluoro-7-nitrobenz-2-oxa-1,3- diazole in in the presence of a base; to afford said compound of formula (I). In one embodiment, said fluorescent label containing a carboxylic acid moiety in reaction (a) is selected from: , , p , and p ; wherein: X, Y, V, W, and p are as defined herein. In one embodiment, said coupling reagent in reaction (a) is selected from DCC, HATU, EDCI, HOBt, TBTU, and T3P. In one embodiment, said base in reaction (a) is selected from Huenig’s base, triethyl amine, and DMAP. In one embodiment, said reaction (a) is conducted in a suitable solvent solvent, preferably in a solvent selected from N,N-dimethylformamide, DMA, DCM, and dioxane. In one embodiment, said fluorescent label containing an N-hydroxisuccinimide (NHS) activated ester in reaction (b) is selected from: , , p , and p ; wherein: X, Y, V, W, and p are as defined herein. In one embodiment, said base in reaction (b) is selected from N,N-diisopropylethylamine (DIPEA) and 2,6-lutidine. In one embodiment, said reaction (b) is conducted in a suitable solvent solvent, preferably in a solvent selected from DCM, THF, ACN, DMF, and dioxane. In one embodiment, said base in reaction (c) is triethylamine. In one embodiment, said reaction (c) is conducted in a suitable solvent solvent, preferably in methanol. In one aspect, the present invention provides a compound of formula (I) or (II) as described herein, when manufactured according to any one of the processes described herein. MAGL Inhibitory Activity Compounds were profiled for MAGL inhibitory activity by determining the enzymatic activity by following the hydrolysis of the natural substrate 2-arachidonoylglycerol (2-AG) resulting in arachidonic acid, which can be followed by mass spectrometry. This assay is hereinafter abbreviated “2-AG assay”. The 2-AG assay was carried out in 384 well assay plates (PP, Greiner Cat# 784201) in a total volume of 20 µL. Compound dilutions were made in 100% DMSO (VWR Chemicals 23500.297) in a polypropylene plate in 3-fold dilution steps to give a final concentration range in the assay from 12.5 µM to 0.8 pM.0.25µL compound dilutions (100% DMSO) were added to 9 µL MAGL in assay buffer (50 mM TRIS (GIBCO, 15567-027), 1 mM EDTA (Fluka, 03690-100 mL), 0.01% (v/v) Tween. After shaking, the plate was incubated for 15 min at RT. To start the reaction, 10 µL 2-arachidonoylglycerol in assay buffer was added. The final concentrations in the assay was 50 pM MAGL and 8 µM 2- arachidonoylglyerol. After shaking and 30 min incubation at RT, the reaction was quenched by the addition of 40µL of ACN containing 4µM of d8-arachidonic acid. The amount of arachidonic acid was traced by an online SPE system (Agilent Rapidfire) coupled to a triple quadrupole mass spectrometer (Agilent 6460). A C18 SPE cartridge (G9205A) was used in an ACN/water liquid setup. The mass spectrometer was operated in negative electrospray mode following the mass transitions 303.1 259.1 for arachidonic acid and 311.1 267.0 for d8-arachidonic acid. The activity of the compounds was calculated based on the ratio of intensities [arachidonic acid / d8-arachidonic acid]. Table 1 The compounds of formula (I) are fluorescent imaging probes with high affinity for MAGL. They may thus be used as high resolution tools to investigate localization, e.g. expression levels and protein distribution in health and disease, structure, dynamics and function of MAGL in living cells. They may also be applied e.g. in flow cytometry fluorescence-activated cell sorting (FACS) experiments or cellular trafficking studies using confocal live cell imaging. In one aspect, the present invention provides a compound of formula (I) described herein, for use in monoacylglycerol lipase (MAGL) occupancy studies. In a further aspect, the present invention provides a compound of formula (I) described herein, for use in diagnostic imaging of monoacylglycerol lipase (MAGL) in a mammal. In a further aspect, the present invention provides a compound of formula (I) described herein, for use in generating monoacylglycerol lipase (MAGL) equilibrium and kinetic binding data. In a further aspect, the present invention provides using a compound of formula (I) described herein in monoacylglycerol lipase (MAGL) occupancy studies. In a further aspect, the present invention provides using a compound of formula (I) described herein in diagnostic imaging of monoacylglycerol lipase (MAGL) in a mammal. In a further aspect, the present invention provides using a compound of formula (I) described herein for generating monoacylglycerol lipase (MAGL) equilibrium and kinetic binding data. In a further aspect, the present invention provides a method of studying monoacylglycerol lipase (MAGL) occupancy, comprising contacting MAGL with a compound of formula (I) described herein. In a further aspect, the present invention provides a method of diagnostic imaging of monoacylglycerol lipase (MAGL) in a mammal, comprising contacting MAGL with a compound of formula (I) described herein. In a further aspect, the present invention provides a method of generating monoacylglycerol lipase (MAGL) equilibrium and kinetic binding data, comprising contacting MAGL with a compound of formula (I) described herein. The compounds of formula (II) are useful synthetic intermediates for the preparation of the fluorescent probes of formula (I). Thus, in one aspect, the present invention provides the use of a compound of formula (II) described herein for the preparation of a fluorescent probe of formula (I) described herein. Examples The invention will be more fully understood by reference to the following examples. The claims should not, however, be construed as limited to the scope of the examples. In case the preparative examples are obtained as a mixture of enantiomers, the pure enantiomers can be separated by methods described herein or by methods known to the man skilled in the art, such as e.g., chiral chromatography (e.g., chiral SFC) or crystallization. All reaction examples and intermediates were prepared under an argon atmosphere if not specified otherwise. Example 1 Benzyl (2-(2-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)methoxy)methyl)phenoxy)ethyl)carbamat e Step d Ethyl 2-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzoate Ethyl salicylate (CAS RN 118-61-6, 2.26 g, 13.6 mmol) was dissolved in DMF (8 mL), Cs2CO3 (4.43g, 13.6 mmol) was added, and the mixture was stirred at room temperature for five minutes. Next, 2-(((benzyloxy)carbonyl)amino)ethyl 4-methylbenzenesulfonate (CAS RN 93407-96-6, 2.80 g, 8.00 mmol) was added, and mixture was stirred at 55 °C for 18 h. The reaction was quenched by diluting with DCM (60 mL), extracted with aq. sn. 10% NaOH (2 x 40 mL) and washed with brine (50 mL). The organic layer was dried over MgSO ₄ , filtrated and concentrated under reduced pressure. The crude was purified by silica gel flash chromatography (0 to 50% AcOEt in cyclohexane) to afford the title compound (2.54 g, 7.40 mmol, 92%). ¹ H NMR (300 MHz, CDCl3) δ 7.82 (dd, J = 7.8, 1.8 Hz, 1H), 7.45 (ddd, J = 8.2, 7.4, 1.8 Hz, 1H), 7.41 – 7.24 (m, 5H), 7.07 – 6.90 (m, 2H), 5.98 (s, 1H, NHCbz), 5.12 (s, 2H, OCH2), 4.35 (q, J = 7.1 Hz, 2H, OCH2CH3), 4.14 (t, J = 5.0 Hz, 2H, OCH ₂ ), 3.64 (m, 2H, CH ₂ NHCbz), 1.36 (t, J = 7.1 Hz, 3H, OCH ₂ CH ₃ ). ¹³ C NMR (75 MHz, CDCl ₃ ) δ 166.2, 158.44, 156.73 (C=O CO ₂ Et, C=O Cbz, C _Ar -O) 136.8, 133.7, 131.9, 128.6, 128.11, 128.09, 121.1, 120.9, 114.3, 68.8 (OCH2), 66.8 (OCH2), 61.1 (OCH2), 40.6 (CH ₂ NHCbz), 14.4 (CH ₃ ). LC-HRMS (ESI) calc. for C ₁₉ H ₂₁ NO ₅ Na [M+Na] ⁺ : 366.1312; found: 366.1301. Step e Benzyl (2-(2-(hydroxymethyl)phenoxy)ethyl)carbamate Ester ethyl 2-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzoate (1.15 g, 3.35 mmol) was dissolved in toluene (11.2 mL) under N ₂ atmosphere at 0 °C, and a 1M DIBAL in DCM solution (15.1 mL, 15.1 mmol) was added dropwise. The reaction mixture was stirred at 0 °C until completion (1.5 h, TLC monitoring). The reaction was quenched by diluting with DCM (20 mL) and dropwise addition of AcOH (0.86 mL, 15.1 mmol). The mixture was then extracted with 10% aq. sn. NaOH (2 x 40 mL) and washed with brine (40 mL). The organic layer was dried over MgSO4, filtrated and concentrated under reduced pressure. The concentrate was purified by silica gel flash chromatography (0 to 65% AcOEt in cyclohexanes) to afford the title compound (817 mg, 2.71 mmol, 81%). ¹ H NMR (300 MHz, CDCl3) δ 7.39 – 7.20 (m, 4H), 6.95 (td, J = 7.5, 1.1 Hz, 1H), 6.85 (d, J = 8.1 Hz, 1H), 5.12 (s, 2H, OCH ₂ ), 4.66 (s, 2H, OCH ₂ ), 4.10 (t, J = 5.0 Hz, 2H, OCH ₂ ), 3.63 (t, J = 5.0 Hz, 2H, CH2NHCbz). ¹³ C NMR (75 MHz, CDCl3) δ 156.9, 156.7 (C=O Cbz, CAr-O), 136.5, 129.5, 129.4, 129.3, 128.7, 128.3, 121.3, 111.6, 67.6 (OCH2), 67.1 (OCH2), 62.1 (OCH2), 40.8 (CH2-NHCbz). LC-HRMS (ESI) calc. for C17H20NO4 [M+H] ⁺ : 302.1386; found: 302.1365. Step f Benzyl (2-(2-(bromomethyl)phenoxy)ethyl)carbamate Alcohol benzyl (2-(2-(hydroxymethyl)phenoxy)ethyl)carbamate (795 mg, 2.64 mmol) was dissolved in DCM (20.3mL) and cooled to 0 °C. Next, CBr4 (1.00 g, 3.04 mmol) was added followed by PPh3 (796 mg, 3.04 mmol, 1.5 M solution in DCM). The reaction mixture was stirred at r.t. until completion (10 min, TLC monitoring). The reaction was quenched by diluting with DCM (30 mL), extracted with aq. sat. NaHCO ₃ (2 x 30 mL) and washed with brine (20 mL). The organic layer was dried over MgSO4, filtrated and concentrated under reduced pressure. The concentrate was purified by silica gel flash chromatography (0 to 40% AcOEt in cyclohexanes) to afford the title compound (694 mg, 1.90 mmol, 72%). ¹ H NMR (300 MHz, CDCl ₃ ) δ 7.38 – 7.28 (m, 7H), 7.04 – 6.81 (m, 2H), 5.12 (s, 2H, OCH ₂ Cbz), 4.59 (d, J = 27.9 Hz, 2H, CH ₂ -Br), 4.14 (t, J = 4.9 Hz, 2H, OCH ₂ CH ₂ -NHCbz), 3.68 (q, J = 5.3 Hz, 2H, OCH2CH2-NHCbz). ¹³ C NMR (75 MHz, CDCl3) δ 156.7, 136.7, 131.0, 130.6, 128.7, 128.1, 121.2, 111.8, 67.5 (-OCH ₂ -), 66.9 (-OCH ₂ -), 40.7 (-OCH ₂ CH ₂ -NHCbz), 29.7 (CH ₂ -Br). LC-MS (ESI): 386.0 [M+Na] ⁺ . Step g tert-Butyl 3-(((2-(2- tert-Butyl 3-(hydroxymethyl)azetidine-1-carboxylate (CAS RN 142253-56-3, 196 mg, 1.05 mmol) was dissolved in anhydrous THF (7 mL) at 0 °C, KOtBu (118 mg, 1.05 mmol) was added, and the mixture was stirred for 5 min. Next, bromine derivative benzyl (2-(2- (bromomethyl)phenoxy)ethyl)carbamate (254.9 mg, 0.70 mmol) was dissolved in anhydrous THF (1.5 mL) and added dropwise to the reaction mixture. The mixture was then allowed to warm up to r.t. and stirred for 4 h until completion (TLC monitoring). The reaction was quenched by diluting with DCM (10 mL) and dropwise addition of AcOH (0.1 mL, 1.05 mmol). The mixture was extracted with aq. sat. NaHCO3 (2 x 20 mL) and washed with brine (20 mL). The organic layer was dried over MgSO ₄ , filtrated and concentrated under reduced pressure. The concentrate was purified by silica gel flash chromatography (0 to 40% AcOEt in cyclohexanes) to afford the title compound (186 mg, 0.40 mmol, 57%). ¹ H NMR (300 MHz, CDCl3) δ 7.39 – 7.23 (m, 7H), 6.96 (td, J = 7.4, 1.0 Hz, 1H), 6.85 (d, J = 8.2 Hz, 1H), 5.50 (s, 1H, NHCbz), 5.10 (s, 2H, OCH ₂ ), 4.54 (s, 2H, OCH ₂ ), 4.14 – 4.03 (m, 2H, OCH ₂ ), 3.86 (t, J = 8.4 Hz, 2H, OCH2), 3.67 – 3.51 (m, 6H, CH2NHCbz, 2 x N-CH2 azetidine), 2.78 – 2.63 (m, 1H, CH azetidine), 1.43 (s, 9H, 3 x CH3 Boc). 13C NMR (75 MHz, CDCl3) δ 156.5, 136.5, 129.9, 129.4, 128.7, 128.44, 128.38, 126.7, 121.2, 112.1, 79.4 (C(CH ₃ ) Boc), 72.7 (CH azetidine), 68.8 (OCH2), 67.6 (OCH2), 67.0 (OCH2), 40.8 (CH2-NHCbz), 28.5 (CH3 Boc). LC-HRMS (ESI) calc. for C26H35N2O6 [M+H] ⁺ : 471.2490; found: 471.2475. Step a1 Benzyl (2-(2-(((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)azetidin-3-yl)methoxy)methyl)phenoxy)ethyl)carbamat e 1. Boc deprotection N-Boc protected derivative tert-Butyl 3-(((2-(2- (((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)methyl)azetidi ne-1-carboxylate (BB1, 93.0 mg, 0.20 mmol) was dissolved in DCM (1.3 mL) at 0 °C and TFA (152 µL, 2.0 mmol) was added. The reaction mixture was stirred at that temperature until Boc deprotection was complete (1 h, LC-MS monitoring). The reaction was diluted with toluene (3.00 mL), and coevaporated with toluene (3.00 mL) under reduced pressure twice. The 2,2,2- trifluoroacetate salt of the free amine 3-(((2-(2- (((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)methyl)azetidi ne was used in the next step (2) without further purification. 2. Urea coupling (4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxazin-6-ium (2S,3S)- 3-carboxy-2,3-bis((4-methylbenzoyl)oxy)propanoate salt (CAS RN 2624363-49-9, 119 mg, 0.16 mmol) was dissolved in anhydrous acetonitrile (0.7 mL) and1,1′-Carbonyl-di-(1,2,4- triazole) (CAS RN 41864-22-6, 26.3 mg, 0.16 mmol), followed by triethylamine (0.16 mL, 1.12 mmol) were added. The reaction mixture was stirred at room temperature for 2 h. Then, the amine nucleophile from step 1 2,2,2-trifluoroacetate salt of 3-(((2-(2- (((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)methyl)azetidi ne was dissolved in ACN (0.5 mL) and added dropwise to the reaction mixture. The reaction mixture was heated to 50 °C and stirred at that temperature for 2.5 h. The reaction was quenched by diluting with DCM (5.00 mL), extracted with aq. sat. NaHCO ₃ (2.00 mL) and washed with brine (2.00 mL). The organic layer was dried over MgSO4, filtrated and concentrated under reduced pressure. The concentrate was purified by HPLC (25 to 75% ACN in H2O with 0.1% TFA) to afford the title compound (70.0 mg, 0.13 mmol, 79%). ¹ H NMR (300 MHz, MeOD) δ 7.37 – 7.16 (m, 7H, H-Ar), 6.96 – 6.84 (m, 2H, H-Ar), 5.05 (s, 2H, O-CH2-), 4.51 (s, 2H, O- CH2-), 4.25 – 4.06 (m, 2H), 4.06 – 3.88 (m, 4H), 3.82 – 3.62 (m, 3H), 3.58 – 3.45 (m, 4H), 3.32 – 3.20 (m, 3H), 2.99 – 2.83 (m, 2H), 2.80 – 2.66 (m, 1H, -CH- azetidine), 1.90 – 1.64 (m, 2H. –CH ₂ - HHPO). ¹³ C NMR (75 MHz, MeOD) δ 171.2, 163.7 (2 x C=O urea, amide), 158.9, 158.0 (C=O Cbz, Cipso phenol), 138.3, 130.8, 130.3, 129.5, 129.0, 128.8, 127.8, 121.8, 112.9 (C-Ar), 73.0, 70.4, 69.18, 68.21, 68.1, 67.5, 55.2, 55.1, 50.4, 47.1, 41.5, 40.5, 30.4, 30.2. LC-HRMS (ESI) calc. for C29H37N4O7 ⁺ [M+H] ⁺ : 553.2657; found: 553.2665. If not indicated otherwise the following examples were synthesized in analogy to the synthesis described for Example 1 using suitable building blocks. Example 15 Benzyl (2-(2-(((7-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)-7-azaspiro[3.5]nonan-2-yl)oxy)methyl)phenoxy)ethyl )carbamate Step g tert-Butyl 2-((2-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)-7- azaspiro[3.5]nonane-7-carboxylate (BB 13) In analogy to the procedure described in Example 1 g), benzyl (2-(2- (bromomethyl)phenoxy)ethyl)carbamate (see Example 1) was reacted with tert-butyl 6- hydroxy-2-azaspiro[3.3]heptane-2-carboxylate (CAS RN 240401-28-9), to afford the title compound (59.6 mg, 0.114 mmol, 76%). ¹ H NMR (300 MHz, CDCl ₃ ) δ 7.38 – 7.26 (m, 7H), 6.95 (td, J = 7.5, 1.0 Hz, 1H), 6.85 (d, J = 8.2 Hz, 1H), 5.57 (s, 1H, NHCbz), 5.10 (s, 2H, OCH2), 4.41 (s, 2H, OCH2), 4.16 – 3.95 (m, 3H), 3.61 (q, J = 5.3 Hz, 2H), 3.23 (dt, J = 20.9, 5.7 Hz, 4H), 2.12 (t, J = 10.0 Hz, 2H), 1.80 – 1.57 (m, 3H), 1.45 (m, 12H). ¹³ C NMR (75 MHz, CDCl ₃ ) δ 156.7, 155.1 (C=O Cbz, C=O Boc, C _Ar -O), 136.6, 130.1, 129.4, 128.7, 128.4, 128.3, 126.9, 121.2, 112.2, 79.4 (C(CH ₃ ) ₃ Boc), 69.1, 67.7, 67.0, 65.7, 41.0, 40.9, 40.8, 39.6, 39.4, 36.7, 31.0, 28.6 (3 x CH3 Boc), 27.1. LC-HRMS (ESI) calc. for C ₃₀ H ₄₀ N ₂ O ₆ Na [M+Na] ⁺ : 547.2779; found: 547.2799. Step a1 Benzyl (2-(2-(((7-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine-6- carbonyl)-7-azaspiro[3.5]nonan-2-yl)oxy)methyl)phenoxy)ethyl )carbamate 1. Boc deprotection. In analogy to the procedure described in Example 1 a1, step (1), tert- Butyl 2-((2-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)-7-az aspiro[3.5]nonane-7- carboxylate (BB 13) (52.5 mg, 0.10 mmol) was dissolved in DCM (0.7 mL) at 0 °C and TFA (0.11 mL, 1.40 mmol) was added. The reaction mixture was stirred at that temperature until Boc deprotection was complete (30 min, LC-MS monitoring). The reaction was diluted with toluene (3.00 mL), and coevaporated with toluene (3.00 mL) under reduced pressure twice. The trifluoroacetate salt of the free amine was used in the next step without further purification. 2. Urea coupling. Triphosgene (CAS RN 32315-10-9, 53.8 mg, 0.10 mmol) and NaHCO3 (33.6 mg, 0.08 mmol) were suspended in DCM (1.0 mL) at 0 °C. The deprotected amine derivative of Benzyl (2-(2-(((7-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]ox azine- 6-carbonyl)-7-azaspiro[3.5]nonan-2-yl)oxy)methyl)phenoxy)eth yl)carbamate obtained in step a1, 1) was dissolved in anhydrous DCM (1.5 mL) and added dropwise to the triphosgene mixture. The mixture was allowed to warm to r.t. and stirred overnight. The filtrate of this solution was then added dropwise at 0 °C to a solution of (4aR,8aS)-hexahydro-2H- pyrido[4,3-b][1,4]oxazin-3(4H)-one (CAS RN 2377107-31-6, 15.6 mg, 0.10 mmol) and DIPEA (70.0 µL, 0.40 mmol) in DCM (1.0 mL). The mixture was allowed to warm to r.t. and stirred for an additional 3 h. The mixture was concentrated in vacuo and purified by RP- HPLC (25 to 75% ACN in H2O with 0.1% TFA). To afford the title compound (23.6 mg, 39.0 µmol, 39%). ¹ H NMR (300 MHz, MeOD) δ 7.37 – 7.19 (m, 7H), 6.91 (td, J = 8.3, 1.4 Hz, 2H), 5.08 (s, 2H, OCH ₂ ), 4.42 (s, 2H, OCH ₂ ), 4.24 – 4.00 (m, 5H), 3.96 (d, J = 3.0 Hz, 1H), 3.59 (dd, J = 12.7, 5.1 Hz, 1H), 3.52 (t, J = 5.4 Hz, 2H), 3.44 – 3.32 (m, 2H), 3.17 – 2.89 (m, 6H), 2.21 – 2.09 (m, 2H), 1.92 – 1.82 (m, 2H), 1.77 – 1.64 (m, 2H), 1.56 – 1.41 (m, 4H). ¹³ C NMR (75 MHz, CDCl3) δ 171.2, 165.5, 158.9, 158.1 (C=O urea, C=O amide, C=O Cbz, CAr-O), 138.4, 130.9, 130.3, 129.5, 129.0, 128.7, 127.9, 121.8, 112.8, 70.6, 70.3, 68.2, 67.5, 66.2, 50.4, 45.2, 45.1, 42.9, 41.6, 40.6, 40.4, 37.7, 32.3, 30.3. LC-HRMS (ESI) calc. for C ₃₃ H ₄₂ N ₄ O ₇ Na [M+Na] ⁺ : 629.2946; found: 629.2961. If not indicated otherwise the following examples were synthesized in analogy to the synthesis described for Example 15 using suitable building blocks. Example 17 Benzyl (R)-(2-(2-(((1-(3-(2-oxooxazolidin-4-yl)propanoyl)azetidin-3 - yl)methoxy)methyl)phenoxy)ethyl)carbamate Synthesis of the building block: 3-[(4R)-2-Oxooxazolidin-4-yl]propanoic acid (3 steps) Step 1) Methyl (S)-4-((tert-butoxycarbonyl)amino)-5-hydroxypentanoate To a solution of (R)-2-((tert-butoxycarbonyl)amino)-5-methoxy-5-oxopentanoic acid (1 g, 3.83 mmol, CAS: 76379-01-6) in THF (15 mL) at -10 °C was added N-methylmorpholine (421 µL, 3.83 mmol), followed by ethyl chloroformate (368 µL, 3.83 mmol) and the reaction mixture was stirred at this temperature for 10 minutes. Addition of NaBH ₄ (434 mg, 11.5 mmol) in one portion did not cause a temperature increase. MeOH (35 mL) was added dropwise between -1°C and 17 °C over 30 min. Stirring was continued in an ice bath for 1 h. A 1 M aqueous KHSO4 sol. (40 mL) was added dropwise to the reaction mixture and then the organic solvents were evaporated under reduced pressure. The aqueous layer was extracted twice with ethyl acetate. The combined organic layers were washed with aqueous 1 M KHSO4 solution and sat. aqueous NaHCO3 solution, dried over MgSO4, filtered, treated with silica gel and evaporated under reduced pressure. The crude compound was purified by silica gel chromatography using a MPLC system eluting with a gradient of n-heptane : ethyl acetate (100 : 0 to 30 : 70) to get the title compound as a colorless oil (0.70 g, 66 %). MS (ESI): m/z = 192.1 [M+H] ⁺ . Step 2) Methyl (R)-3-(2-oxooxazolidin-4-yl)propanoate To a solution of methyl (S)-4-((tert-butoxycarbonyl)amino)-5-hydroxypentanoate (690 mg, 2.79 mmol, 1.0 equiv) in THF (8.8 mL) was added dropwise thionyl chloride (611 µL, 8.37 mmol,3.0 equiv) and the solution was stirred at r.t. for 3 h. Silica gel was added and the reaction mixture was evaporated under reduced pressure. The compound was purified by silica gel chromatography using a MPLC system eluting with a gradient of n-heptane : ethyl acetate (100 : 0 to 0 : 100) to afford the title compound as a colorless oil (404 mg, 79 %). MS (ESI): m/z = 174.1 [M+H] ⁺ . Step 3) (R)-3-(2-Oxooxazolidin-4-yl)propanoic acid To a solution of methyl (S)-3-(2-oxooxazolidin-4-yl)propanoate (400 mg, 2.31 mmol, 1.0 equiv) in 1,4-dioxane (2 mL) and water (2 mL) was added lithium hydroxide monohydrate (107 mg, 2.54 mmol, 1.1 equiv) and the reaction mixture was stirred at r.t. for 2 h. 1,4- Dioxane was evaporated and aqueous HCl (2.54 mL, 2.54 mmol, 1.1 equiv) was added dropwise to the solution. The aqueous layer was extracted five times with ethyl acetate. The combined organic layers were dried over MgSO ₄ , filtered and evaporated to get the title compound as a colorless solid (330 mg, 86 %). MS (ESI): m/z = 160.1 [M+H] ⁺ . Step a2 (R)-(2-(2-(((1-(3-(2-oxooxazolidin-4-yl)propanoyl)azetidin-3 - yl)methoxy)methyl)phenoxy)ethyl)carbamate (R)-3-(2-oxooxazolidin-4-yl)propanoic acid (12.7 mg, 0.08 mmol) was dissolved in THF/ACN 1:1 (1.60 mL) and then DIPEA (42.0 µL, 0.24 mmol) followed by HATU (36.5 mg, 96.0 µmol) were added. After stirring for 10 min the deprotected amine derivative of tert-butyl 3-(((2-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)meth yl)azetidine-1- carboxylate BB1 (38.7 mg, 0.08 mmol, prepared as described for Example 1, step 1, Boc deprotection) was added. The mixture was stirred at r.t. overnight and then the mixture was directly diluted with ACN/H2O and purified by RP-HPLC (15-85% ACN in H2O with 0.1% TFA) to afford the title compound (16.3 mg, 0.032 mmol, 40%). LC-HRMS (ESI) calc. for C ₂₇ H ₃₄ N ₃ O ₇ [M+H] ⁺ : 512.2389; found: 512.2391. Example 18 Benzyl (2-(2-(((1-(3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carb onyl)azetidin-3- yl)methoxy)methyl)phenoxy)ethyl)carbamate In analogy to the procedure described in Example 17, step a2, tert-butyl 3-(((2-(2- (((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)methyl)azetidi ne-1-carboxylate BB1 was reacted with 3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylic acid (CAS RN: 134997-87-8) to afford the title compound (22.3 mg, 0.0.41 mmol, 50%). LC-HRMS (ESI) calc. for C30H32N3O7 [M+H] ⁺ : 546.2235; found: 546.2239. Example 19 2-(6-(2-(2-((7-nitro-1l2,3l2-benzo[c][1,2,5]oxadiazol-4-yl)a mino)ethoxy)benzyl)-2- azaspiro[3.3]heptane-2-carbonyl)-7-oxa-2,5-diazaspiro[3.4]oc tan-6-one Step b 2-(6-(2-(2-aminoethoxy)benzyl)-2-azaspiro[3.3]heptane-2-carb onyl)-7-oxa-2,5- diazaspiro[3.4]octan-6-one A mixture of 20% tBuOH in EtOAc (HPLC grade) was purged with N2 for at least 15 min and kept under N2 atmosphere on a closed vial. In a pear-shaped flask, the starting material benzyl (2-(2-((2-(6-oxo-7-oxa-2,5-diazaspiro[3.4]octane-2-carbonyl) -2- azaspiro[3.3]heptan-6-ylidene)methyl)phenoxy)ethyl)carbamate (Example 13, 16.0 mg, 0.03 mmol) was dissolved in the previously prepared solvent mixture and purged with N ₂ for 10 min. Next, Palladium on Carbon (10 mol%) was added to the mixture and further purged with N ₂ for additional 15 min. Using a H ₂ -filled balloon, the reaction was then carried with constant bubbling of H ₂ through the solution until completion (LC-MS monitoring). Solvent mixture levels were kept at 1-2 mL by adding small amounts of the previously prepared N2-purged solvent mixture when needed. Palladium on carbon was removed from reaction the mixture by filtration with a PTFE syringe filter (pore size: 0.45 μm) using ACN and water to wash the filter. The crude was lyophilized and the obtained title compound was used in next step (step c) without further purification.LC-MS [M+H] ⁺ : 400.9. Step c 2-(6-(2-(2-((7-nitro-1l2,3l2-benzo[c][1,2,5]oxadiazol-4-yl)a mino)ethoxy)benzyl)-2- azaspiro[3.3]heptane-2-carbonyl)-7-oxa-2,5-diazaspiro[3.4]oc tan-6-one 2-(6-(2-(2-aminoethoxy)benzyl)-2-azaspiro[3.3]heptane-2-carb onyl)-7-oxa-2,5- diazaspiro[3.4]octan-6-one (12.0 mg, 0.03 mmol) from step c) was dissolved in MeOH (0.75 mL) and trimethylamine (13.0 µL, 0.09 mmol) was added. Next, a solution of 4-fluoro-7- nitrobenz-2-oxa-1,3-diazole (CAS RN 29270-56-2, 11.0 mg, 0.06 mmol) in MeOH (0.3 mL) was added dropwise. The reaction was stirred in the dark for 3.5 h. Next, the solvent was removed in vacuo at 20 °C and the reaction was purified through RP-HPLC 15-85% ACN in H2O with 0.1% TFA to afford the title product (3.19 mg, 6.0 µmol, 19%). ¹ H NMR (600 MHz, CD3CN) δ 8.53 (d, J = 8.8 Hz, 1H), 7.16 (td, J = 7.8, 1.7 Hz, 1H), 7.06 (dd, J = 7.4, 1.7 Hz, 1H), 6.92 (dd, J = 8.3, 1.1 Hz, 1H), 6.87 (td, J = 7.4, 1.1 Hz, 1H), 6.51 – 6.39 (m, 2H), 4.47 (s, 2H), 4.27 (t, J = 5.0 Hz, 2H), 4.05 – 3.83 (m, 6H), 3.67 (s, 2H), 3.60 (s, 2H), 2.55 (d, J = 7.5 Hz, 2H), 2.26 (p, J = 7.8 Hz, 1H), 2.03 – 1.96 (m, 2H), 1.75 – 1.68 (m, 2H). ¹³ C NMR (151 MHz, CD ₃ CN) δ 162.19, 157.44, 156.29, 144.81, 137.33, 130.22, 129.00, 127.24, 120.80, 111.37, 74.18, 65.81, 62.84, 62.43, 61.60, 54.21, 38.31, 36.10, 34.53, 29.56. LC-HRMS (ESI) calc. for C27H30N7O7 [M+H] ⁺ : 564.2201; found: 564.2192. If not indicated otherwise the following examples were synthesized in analogy to the synthesis described for Example 19 using suitable building blocks.

Example 26 2-(7-(Dimethylamino)-3-(dimethyliminio)-5,5-dimethyl-3,5-dih ydrodibenzo[b,e]silin- 10-yl)-4-((5-(2-((2-(6-oxo-7-oxa-2,5-diazaspiro[3.4]octane-2 -carbonyl)-2- azaspiro[3.3]heptan-6-yl)methyl)phenoxy)pentyl)carbamoyl)ben zoate Step b 2-(6-(2-((5-aminopentyl)oxy)benzyl)-2-azaspiro[3.3]heptane-2 -carbonyl)-7-oxa- 2,5-diazaspiro[3.4]octan-6-one In analogy to the procedure described in example 19 b), benzyl (5-(2-((2-(6-oxo-7-oxa-2,5- diazaspiro[3.4]octane-2-carbonyl)-2-azaspiro[3.3]heptan-6- ylidene)methyl)phenoxy)pentyl)carbamate (Example 14) was treated with hydrogen and palladium on carbon to afford the title compound, which used in next step (step c) without further purification. LC-MS [M+H] ⁺ : 442.9. Step c 2-(7-(Dimethylamino)-3-(dimethyliminio)-5,5-dimethyl-3,5- dihydrodibenzo[b,e]silin-10-yl)-4-((5-(2-((2-(6-oxo-7-oxa-2, 5-diazaspiro[3.4]octane-2- carbonyl)-2-azaspiro[3.3]heptan-6-yl)methyl)phenoxy)pentyl)c arbamoyl)benzoate 2-(6-(2-((5-aminopentyl)oxy)benzyl)-2-azaspiro[3.3]heptane-2 -carbonyl)-7-oxa-2,5- diazaspiro[3.4]octan-6-one (8.96 mg, 0.02 mmol) was dissolved in ACN with 10% DMF (0.90 mL) at 0 °C, then the 2-(7-(dimethylamino)-3-(dimethyliminio)-5,5-dimethyl-3,5- dihydrodibenzo[b,e]silin-10-yl)-4-(((2,5-dioxopyrrolidin-1-y l)oxy)carbonyl)benzoate (CAS RN 1426090-09-6, 5.00 mg, 9.0 µmol) followed by DIPEA (9.0 µL, 7.0 µmol) were added. The reaction was stirred at room in the dark for approximately 4h (LC-MS monitoring of the reaction). Then diluted with H ₂ O/ACN and freeze dried. The crude was purified by RP-HPLC H ₂ O/ACN with 0.1% TFA 25 to 75% in 30 min to afford the target product (6.0 mg, 7.0 µmol, 76%). ¹ H NMR (600 MHz, MeOD) δ 8.33 (d, J = 8.2 Hz, 1H), 8.14 (dd, J = 8.2, 1.8 Hz, 1H), 7.74 (d, J = 1.7 Hz, 1H), 7.36 (d, J = 2.9 Hz, 2H), 7.13 (td, J = 7.8, 1.7 Hz, 1H), 7.04 (dd, J = 7.4, 1.7 Hz, 1H), 7.02 – 6.99 (m, 2H), 6.88 (dd, J = 8.2, 1.1 Hz, 1H), 6.83 (td, J = 7.3, 1.0 Hz, 1H), 6.77 (dd, J = 9.6, 2.9 Hz, 2H), 4.53 (s, 2H, OCH2), 4.07 (s, 4H, OCH2), 4.00 (t, J = 6.1 Hz, 2H), 3.93 (s, 2H), 3.84 (s, 2H), 3.47 (t, J = 7.1 Hz, 2H), 3.32 (s, 12H, 4 x N-CH ₃ ), 2.64 (d, J = 7.4 Hz, 2H), 2.44 (p, J = 7.7 Hz, 1H, CH spirocycle), 2.22 – 2.16 (m, 2H, CH-CH ₂ -C spirocycle), 1.88 (ddd, J = 10.5, 7.9, 2.8 Hz, 4H, CH-CH2-C spirocycle, -CH2- alkyl), 1.74 (p, J = 7.2 Hz, 2H, -CH2- alkyl), 1.67 – 1.59 (m, 2H, -CH ₂ - alkyl), 0.68 (s, 3H, Si-CH ₃ ), 0.62 (s, 3H, Si-CH ₃ ). ¹³ C NMR (151 MHz, MeOD) δ 166.6, 162.3, 159.0, 156.8 (C=O urea, C=O carbamate, COO-, CAr-O), 129.7, 128.5, 127.4, 126.9, 120.1, 119.8, 113.8, 110.9, 74.2 (OCH2), 67.2 (OCH2), 63.0, 62.4, 61.8, 54.4 (-C- carbamate spirocycle), 39.8, 39.6, 38.2, 36.0, 34.7 (-C- spirocycle), 29.7 (CH spirocycle), 28.9, 28.8 (-CH ₂ - alkyl), 23.5 (-CH ₂ - alkyl), -2.20 (Si-CH ₃ ), -3.09 (Si-CH ₃ ). LC-HRMS (ESI) calc. for C51H60N6O7Si [M+H] ⁺ : 897.4366; found: 897.4357. If not indicated otherwise the following examples were synthesized in analogy to the synthesis described for Example 26 using suitable building blocks. Example 32 is a regioisomeric mixture of 5- and 6-carboxytetramethylrhodamine derivatives that was obtained in one reaction. HPLC purification allowed to separate a fraction ofthe 5- carboxytetramethylrhodamine derivative (example 33) from the mixture. The respective 6- carboxytetramethylrhodamine derivative could not be obtained in pure form. The same considerations apply to examples 34 and 35 and 36 and 37, respectively. Example 38 was obtained as 5- and 6-carboxytetramethylrhodamine derivative regioisomeric mixture.

Example 39 Ethyl 3-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine -6- carbonyl)azetidin-3-yl)methoxy)benzoate Step d tert-butyl 3-((3-(ethoxycarbonyl)phenoxy)methyl)azetidine-1-carboxylate (BB15) In analogy to the procedure described in Example 1 d), ethyl 3-hydroxy benzoate (CAS RN 7781-98-8) was reacted with tert-butyl 3-(bromomethyl)azetidine-1-carboxylate (CAS RN 253176-93-1) to afford the title compound (18.0 mg, 0.05 mmol, 18%). LC-MS (ESI) [M+Na] ⁺ . [M+Na] ⁺ : 338.1 Step a1 Ethyl 3-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine -6- carbonyl)azetidin-3-yl)methoxy)benzoate In analogy to the procedure described in Example 1, a1), (4aR,8aS)-3-oxooctahydro-2H- pyrido[4,3-b][1,4]oxazin-6-ium (2S,3S)-3-carboxy-2,3-bis((4- methylbenzoyl)oxy)propanoate salt (CAS RN 2624363-49-9, 66.7 mg, 0.09 mmol) was reacted with the deprotected amine derivative of tert-butyl 3-((3- (ethoxycarbonyl)phenoxy)methyl)azetidine-1-carboxylate BB15 (33.5 mg, 0.10 mmol prepared as described for Example 1, step 1, Boc deprotection) to afford the title compound (16.3 mg, 0.032 mmol, 40%). LC-MS (ESI) [M+H] ⁺ : 418.2. If not indicated otherwise the following examples were synthesized in analogy to the synthesis described for Example 39 using suitable building blocks. Example 42 tert-Butyl (2-(3-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxa zine-6- carbonyl)azetidin-3-yl)oxy)benzamido)ethyl)carbamate

Step k 1. Ester hydrolysis. Ethyl 3-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3- b][1,4]oxazine-6-carbonyl)azetidin-3-yl)oxy)benzoate (Example 40, 12.5 mg, 0.03 mmol) was dissolved in THF/MeOH/H2O 3:1:1 (0.2 mL) and lithium hydroxide (LiOH, 2,15 mg, 0.09 mmol) was added. The reaction was stirred at room temperature until completion (ca. 2h). The reaction was quenched by diluting with ethyl acetate (1.0 mL), extracted with aq. sn. 1 M HCl (0.5 mL), and washed with brine (0.5 mL). The organic layer was dried over MgSO4, filtrated, and solvent was removed in vacuo. The carboxylic acid 3-((1-((4aR,8aS)- 3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azeti din-3-yl)oxy)benzoic acid was used in the next step without further purification. 2. Amide coupling. 3-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine -6- carbonyl)azetidin-3-yl)oxy)benzoic acid crude obtained in step 1 from Ethyl 3-((1- ((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine-6-car bonyl)azetidin-3- yl)oxy)benzoate (Example 40) was dissolved in DMF (0.43 mL) and DIPEA (16.0 µL, 0.09 mmol) followed by 1-[Bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyri dinium 3-oxid hexafluorophosphate (HATU, CAS RN 148893-10-1, 13.7 mg, 0.04 mmol) were added. The mixture was stirred for 10 min, and then tert-butyl (2-aminoethyl)carbamate (CAS RN 57260-73-8, 5.28 mg, 0.03 mmol) was added. The mixture was stirred at room temperature for 18 h, then diluted with ethyl acetate (1.0 mL, washed with brine (0.5 mL), dried over Na2SO4, filtrated and concentrated under reduced pressure. The crude was purified by RP-HPLC H2O/ACN with 0.1% TFA 25 to 75% to afford the title compound (5.0 mg, 0.01 mmol, 32%). LC-HRMS (ESI) calc. for C ₂₅ H ₃₆ N2O ₇ [M+H]+: 518.2609; found: 518.2601. Example 43 tert-Butyl (2-(2-((1-((4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxa zine-6- carbonyl)azetidin-3-yl)methoxy)benzamido)ethyl)carbamate In analogy to the procedure described in Example 42, k) Ethyl 2-((1-((4aR,8aS)-3- oxooctahydro-2H-pyrido[4,3-b][1,4]oxazine-6-carbonyl)azetidi n-3-yl)methoxy)benzoate (Example 41) was subjected to ester hydrolysis (step k, 1) and then reacted with tert-butyl (2-aminoethyl)carbamate (CAS RN 57260-73-8, 5.28 mg, 0.03 mmol) to afford the title compound (5.0 mg, 9.0 µmol, 55%). LC-MS (ESI) [M+H] ⁺ : 532.2. Example 44 (4aR,8aS)-6-(3-((benzyloxy)methyl)azetidine-1-carbonyl)hexah ydro-2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one Step l tert-Butyl 3-((benzyloxy)methyl)azetidine-1-carboxylate tert-Butyl 3-(hydroxymethyl)azetidine-1-carboxylate (CAS RN 142253-56-3, 103 mg, 0.55 mmol) and sodium hydride 60% dispersion in mineral oil (CAS RN 7646-69-7, 55.0 mg, 1.38 mmol) were suspended in anhydrous DMF (2.0 mL) at 0 °C for 15 min, or until no gas evolution was seen. Then benzyl bromide (CAS RN 100-39-0, 0.16 mL, 1.38 mmol) was added. The reaction was allowed to warm up to room temperature and was stirred for 16 h. The mixture was diluted with dichloromethane (10.0 mL), neutralized with acetic acid, extracted with aq. sat. NaHCO3 (10 mL) and washed with water (10 mL). The organic layer was dried over MgSO ₄ , filtrated, and concentrated in vacuo. The crude was purified via silica gel flash chromatography using ethyl acetate in cyclohexane 0 to 80% as eluent, to afford the title compound (120 mg, 0.43 mmol, 77%). ¹ H NMR (300 MHz, CDCl3) δ 7.40 – 7.26 (m, 5H), 3.99 (t, J = 8.5 Hz, 2H), 3.66 (dd, J = 8.7, 5.3 Hz, 2H), 3.58 (d, J = 6.8 Hz, 2H), 2.88 – 2.67 (m, 1H), 1.43 (s, 9H). LC-MS [M+Na] ⁺ : 300.1. step a1 (4aR,8aS)-6-(3-((benzyloxy)methyl)azetidine-1-carbonyl)hexah ydro-2H- pyrido[4,3-b][1,4]oxazin-3(4H)-one In analogy to the procedure described in Example 1, a1), tert-Butyl 3- ((benzyloxy)methyl)azetidine-1-carboxylate was reacted with 4aR,8aS)-3-oxooctahydro- 2H-pyrido[4,3-b][1,4]oxazin-6-ium (2S,3S)-3-carboxy-2,3-bis((4- methylbenzoyl)oxy)propanoate salt (CAS RN 2624363-49-9) to afford the title compound. LC-MS (ESI) [M+H] ⁺ : 360.1. Example 45 (4aR,8aS)-6-(6-(benzyloxy)-2-azaspiro[3.3]heptane-2-carbonyl )hexahydro-2H- pyrido[4,3-b][1,4]oxazin-3(4H)-one Step l tert-Butyl 6-(benzyloxy)-2-azaspiro[3.3]heptane-2-carboxylate In analogy to the procedure described in Example 44 l), tert-butyl 6-hydroxy-2- azaspiro[3.3]heptane-2-carboxylate (CAS RN 1147557-97-8) was reacted with benzyl bromide (CAS RN 100-39-0) to afford the title compound. ¹ H NMR (300 MHz, CDCl3) δ 7.41 – 7.27 (m, 5H), 4.39 (s, 2H), 4.02 – 3.75 (m, 5H), 2.46 (ddd, J = 9.8, 6.8, 3.0 Hz, 2H), 2.14 (ddd, J = 10.1, 7.3, 3.0 Hz, 2H), 1.42 (s, 9H). Step a1 (4aR,8aS)-6-(6-(benzyloxy)-2-azaspiro[3.3]heptane-2-carbonyl )hexahydro-2H- pyrido[4,3-b][1,4]oxazin-3(4H)-one In analogy to the procedure described in Example 1, a1), tert-Butyl 6-(benzyloxy)-2- azaspiro[3.3]heptane-2-carboxylate was reacted with 4aR,8aS)-3-oxooctahydro-2H- pyrido[4,3-b][1,4]oxazin-6-ium (2S,3S)-3-carboxy-2,3-bis((4- methylbenzoyl)oxy)propanoate salt (CAS RN 2624363-49-9) to afford the title compound. LC-MS (ESI) [M+H] ⁺ : 386.2. Example 46 (4aR,8aS)-6-(3-(phenoxymethyl)azetidine-1-carbonyl)hexahydro -2H-pyrido[4,3- b][1,4]oxazin-3(4H)-one In analogy to the procedure described in Example 1 a1) tert-butyl 3- (phenoxymethyl)azetidine-1-carboxylate (obtained from phenol, CAS RN 108-95-2, and tert-butyl 3-(bromomethyl)azetidine-1-carboxylate, CAS RN 253176-93-1, in analogy to example 1d) was reacted with 4aR,8aS)-3-oxooctahydro-2H-pyrido[4,3-b][1,4]oxazin-6- ium (2S,3S)-3-carboxy-2,3-bis((4-methylbenzoyl)oxy)propanoate salt (CAS RN 2624363- 49-9) to afford the title compound. LC-MS (ESI) [M+H] ⁺ : 346.1 Building block synthesis BB2 tert-Butyl 3-((2-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)azeti dine-1- carboxylate In analogy to the procedure described in Example 1 g), tert-butyl 3-hydroxy-azetidine-1- carboxylate (CAS RN 141699-55-0, 125 mg, 0.72 mmol) was reacted with benzyl (2-(2- (bromomethyl)phenoxy)ethyl)carbamate (see Example 1, 131 mg, 0.36 mmol) to afford the title compound (101 mg, 0.22 mmol, 61%). ¹ H NMR (300 MHz, CDCl ₃ ) δ 7.41 – 7.27 (m, 7H), 6.97 (t, J = 7.4 Hz, 1H), 6.86 (d, J = 8.1 Hz, 1H), 5.43 (s, 1H, NH-Cbz), 5.11 (s, 2H, OCH2-Ar), 4.46 (s, 2H, OCH2 Cbz), 4.31 (dq, J = 10.8, 5.1 Hz, 1H, CH azetidine), 4.10 (t, J = 5.0 Hz, 2H), 4.07 – 3.97 (m, 2H), 3.92 – 3.81 (m, 2H), 3.62 (q, J = 5.4 Hz, 2H, OCH2CH2- NHCbz), 1.42 (d, J = 1.0 Hz, 9H, CH ₃ Boc). ¹³ C NMR (75 MHz, CDCl ₃ ) δ 156.6, 156.5 (C=O Cbz, C=O urea), 136.6, 130.1, 129.7, 128.7, 128.4, 128.3, 121.3, 112.0 (C-Ar), 79.7 (CH Boc), 67.6, 67.0, 66.5 (3 x OCH2), 56.65, 40.8 (CH2-NHCbz), 28.5 (CH3 Boc). LC- HRMS (ESI) calc. for C ₂₅ H ₃₃ N ₂ O ₆ [M+H] ⁺ : 457.2333; found: 457.2320. BB3 tert-Butyl 6-((2-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)-2- azaspiro[3.3]heptane-2-carboxylate In analogy to the procedure described in Example 1 g), benzyl (2-(2- (bromomethyl)phenoxy)ethyl)carbamate (see Example 1) was reacted with tert-butyl 6- hydroxy-2-azaspiro[3.3]heptane-2-carboxylate (CAS RN 1147557-97-8), to afford the title compound (48.5 mg, 0.098 mmol, 65%). ¹ H NMR (300 MHz, CDCl ₃ ) δ 7.39 – 7.21 (m, 7H), 6.95 (td, J = 7.5, 1.0 Hz, 1H), 6.84 (d, J = 8.5 Hz, 1H), 5.54 (s, 1H, NHCbz), 5.10 (s, 2H, OCH2), 4.40 (s, 2H, OCH2), 4.10 (t, J = 5.0 Hz, 2H), 3.93 – 3.72 (m, 5H, CH spirocycle, 2 x NCH ₂ spirocycle), 3.61 (q, J = 5.3 Hz, 2H, CH ₂ NHCbz), 2.41 – 2.28 (m, 2H, C-CH ₂ -CH spirocycle), 2.14 – 1.95 (m, 2H, C-CH2-CH spirocycle), 1.43 (s, 9H, 3 x CH3 Boc). ¹³ C NMR (75 MHz, CDCl3) δ 156.7, 156.6, 156.2 (C=O Cbz, C=O Boc, CAr-O), 136.5, 130.1, 129.5, 128.7, 128.5, 128.4, 126.6, 121.2, 112.1, 79.4 (C(CH ₃ ) ₃ Boc), 68.1, 67.6, 67.0, 65.8, 61.8, 60.5, 41.2, 40.7 (CH2NHCz, 2 x C-CH2-CH spirocycle), 30.1 (-C- spirocycle), 28.5 (3 x CH3 Boc). LC-HRMS (ESI) calc. for C28H36N2O6Na [M+Na] ⁺ : 519.2466; found: 519.2450. BB4 tert-Butyl 7-((2-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)-2- azaspiro[3.5]nonane-2-carboxylate In analogy to the procedure described in Example 1 g), benzyl (2-(2- (bromomethyl)phenoxy)ethyl)carbamate (see Example 1) was reacted with tert-butyl 7- hydroxy-2-azaspiro[3.5]nonane-2-carboxylate (CAS RN 1363383-18-9), to afford the title compound (18.0 mg, 0.05 mmol, 26%). ¹ H NMR (300 MHz, CDCl ₃ ) δ 7.35 (s, 7H), 7.02 – 6.77 (m, 2H), 5.41 (s, 1H, NHCbz), 5.10 (s, 2H, OCH2), 4.53 (s, 2H, OCH2), 4.08 (t, J = 5.0 Hz, 2H), 4.04 – 3.93 (m, 1H), 3.69 – 3.41 (m, 7H), 1.94 – 1.72 (m, 4H), 1.54 – 1.32 (m, 12H). ¹³ C NMR (75 MHz, CDCl ₃ ) δ 156.6, 156.5, 156.2 (C=O Cbz, C=O Boc, C _Ar -O), 136.4, 129.5, 128.9, 128.6, 128.5, 128.2, 128.1, 127.9, 127.4, 121.1, 111.7, 79.2 (C(CH ₃ ) ₃ Boc), 67.3, 66.9, 65.2, 59.0, 40.7 (CH2NHCbz), 34.5, 33.0, 28.5, 28.2 (3 x CH3 Boc). LC- HRMS (ESI) calc. for C ₃₀ H ₄₀ N ₂ O ₆ Na [M+Na] ⁺ : 547.2779; found: 547.2774. BB5 tert-Butyl 3-(((3-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)meth yl)azetidine- 1-carboxylate Step d Ethyl 3-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzoate In analogy to the procedure described in Example 1 d), ethyl 3-hydroxy benzoate (CAS RN 7781 98 8) was reacted with 2-(((benzyloxy)carbonyl)amino)ethyl 4- methylbenzenesulfonate (CAS RN 93407-96-6) to afford the title compound (1.05 g, 3.05 mmol, 61%). ¹ H NMR (300 MHz, CDCl ₃ ) δ 7.66 (dt, J = 7.7, 1.3 Hz, 1H), 7.54 (dd, J = 2.7, 1.5 Hz, 1H), 7.40 – 7.27 (m, 6H), 7.12 – 7.02 (m, 1H), 5.22 (s, 1H, NH-Cbz), 5.12 (s, 2H, OCH2CH3), 4.37 (q, J = 7.1 Hz, 2H, OCH2), 4.09 (t, J = 5.1 Hz, 2H, OCH2), 3.63 (q, J = 5.4 Hz, 2H, CH2NHCbz), 1.39 (t, J = 7.1 Hz, 3H, OCH2CH3). ¹³ C NMR (75 MHz, CDCl3) δ 166.5, 158.5, 156.5 (C=O CO ₂ Et, C=O Cbz, C _Ar -O), 136.5, 132.1, 129.6, 128.7, 128.4, 128.3, 122.6, 119.7, 114.9, 67.3 (OCH2), 67.1 (OCH2), 61.3 (OCH2), 40.7 (CH2NHCbz), 14.5 (CH3). LC-HRMS (ESI) calc. for C19H22NO5 [M+H] ⁺ : 366.1492; found: 366.1508. Step e Benzyl (2-(3-(hydroxymethyl)phenoxy)ethyl)carbamate In analogy to the procedure described in Example 1 e), ethyl 3-(2- (((benzyloxy)carbonyl)amino)ethoxy)benzoate was reacted to afford the title compound (115 mg, 0.38 mmol, 66%). ¹ H NMR (300 MHz, CDCl3) δ 7.43 – 7.16 (m, 6H), 7.00 – 6.85 (m, 2H), 6.87 – 6.70 (m, 1H), 5.11 (s, 2H, O-CH2-), 4.66 (s, 2H, O-CH2-), 4.04 (t, J = 5.1 Hz, 2H, -OCH ₂ CH ₂ NHCbz), 3.60 (d, J = 5.3 Hz, 2H, -OCH ₂ CH ₂ NHCbz). ¹³ C NMR (75 MHz, CDCl3) δ 158.8, 156.6 (C=O Cbz, CAr-O), 142.8, 136.5, 129.8, 128.7, 128.32, 128.28, 119.7, 113.8, 112.9 (C-Ar), 67.01 (O-CH2-), 66.96 (O-CH2-), 65.2 (O-CH2-), 40.7 (-CH2- NHCbz). LC-HRMS (ESI) calc. for C ₁₇ H ₂₀ NO ₄ [M+H] ⁺ : 302.1387; found: 302.1373. Step f Benzyl (2-(3-(bromomethyl)phenoxy)ethyl)carbamate In analogy to the procedure described in Example 1 f), benzyl (2-(3- (hydroxymethyl)phenoxy)ethyl)carbamate was reacted to afford the title compound (503 mg, 1.38 mmol, 63%). ¹ H NMR (300 MHz, CDCl ₃ ) δ 7.42 – 7.22 (m, 6H), 7.03 – 6.97 (m, 1H), 6.95 – 6.90 (m, 1H), 6.88 – 6.79 (m, 1H), 5.24 (s, 1H, NHCbz), 5.13 (s, 2H, OCH ₂ ), 4.46 (s, 2H, CH2Br), 4.06 (t, J = 5.1 Hz, 2H, OCH2), 3.63 (q, J = 5.4 Hz, 2H, CH2NHCbz). ¹³ C NMR (75 MHz, CDCl3) δ 158.8, 156.5 (C=O Cbz, CAr-O), 139.4, 139.2, 136.5, 130.1, 128.7, 128.33, 128.29, 121.9, 121.4, 115.2, 114.7, 114.7, 67.0 (2 x OCH ₂ ), 40.7 (CH2NHCbz), 33.4 (CH2Br). LC-HRMS (ESI) calc. for C17H19BrNO3 [M+H] ⁺ : 366.0524; found: 366.0551. Step g tert-Butyl 3-(((3-(2- (((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)methyl)azetidi ne-1-carboxylate In analogy to the procedure described in Example 1 g), Benzyl (2-(3- (bromomethyl)phenoxy)ethyl)carbamate was reacted with tert-butyl 3- (hydroxymethyl)azetidine-1-carboxylate (CAS RN 142253-56-3) to afford the title compound (85.0 mg, 0.18 mmol, 55%). ¹ H NMR (300 MHz, CDCl3) δ 7.40 – 7.20 (m, 6H), 7.01 – 6.74 (m, 3H), 5.31 – 5.06 (m, 3H, NHCbz, OCH2), 4.70 – 4.42 (m, 3H), 4.07 – 3.91 (m, 4H), 3.74 – 3.51 (m, 5H), 2.88 – 2.69 (m, 1H, CH azetidine), 1.43 (d, J = 1.2 Hz, 9H, 3 x CH3 Boc). LC-HRMS (ESI) calc. for C26H34N2O6Na [M+Na] ⁺ : 493.2309; found: 493.2312 BB6 tert-Butyl 3-((3-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)azeti dine-1- carboxylate In analogy to the procedure described for BB7, Benzyl (2-(3- (bromomethyl)phenoxy)ethyl)carbamate was reacted with tert-butyl 3-hydroxyazetidine-1- carboxylate (CAS RN 141699-55-0), to afford the title compound (55.1 mg, 0.12 mmol, 55%). LC-HRMS (ESI) calc. for C25H33N2O6 [M+H] ⁺ : 457.2333; found: 457.2328. BB7 tert-Butyl 6-((3-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzyl)oxy)-2- azaspiro[3.3]heptane-2-carboxylate In analogy to the procedure described for BB7, Benzyl (2-(3- (bromomethyl)phenoxy)ethyl)carbamate was reacted with tert-butyl 6-hydroxy-2- azaspiro[3.3]heptane-2-carboxylate (CAS RN 1147557-97-8) to afford the title compound (21.0 mg, 0.042 mmol, 28%). ¹ H NMR (300 MHz, CDCl3) δ 7.36 (d, J = 4.9 Hz, 5H), 7.22 (d, J = 7.8 Hz, 1H), 6.93 – 6.74 (m, 3H), 5.11 (s, 2H, OCH ₂ ), 4.35 (s, 2H, OCH ₂ ), 4.04 (t, J = 5.1 Hz, 2H, OCH2), 4.01 – 3.78 (m, 5H, N-CH2-C spirocycle, CH spirocycle), 3.61 (q, J = 5.4 Hz, 2H, CH2NHCbz), 2.47 (m, 2H, C-CH2-CH spirocycle), 2.14 (m, 2H, C-CH2-CH spirocycle), 1.42 (s, 9H, 3 x CH ₃ Boc). ¹³ C NMR (75 MHz, CDCl ₃ ) δ 158.7, 156.5, 156.3 (C=O Cbz, C=O Boc, C _Ar -O), 139.9, 136.5, 129.7, 128.7, 128.34, 128.30, 120.6, 113.8, 79.5 (C(CH3)3 Boc), 70.1, 68.1, 67.0, 61.9, 60.6, 41.2, 40.7, 30.3 (3 x CH3 Boc), 28.5 (-C- spirocycle). LC-HRMS (ESI) calc. for C ₂₈ H ₃₇ N ₂ O ₆ [M+H] ⁺ : 497.2646; found: 497.2636. BB8 tert-Butyl 3-(((2-(3- (((benzyloxy)carbonyl)amino)propoxy)benzyl)oxy)methyl)azetid ine-1-carboxylate Step d Ethyl 2-(3-(((benzyloxy)carbonyl)amino)propoxy)benzoate In analogy to the procedure described in Example 1d), ethyl salicylate (CAS RN 118-61-6) was reacted with 3-(((benzyloxy)carbonyl)amino)propyl 4-methylbenzenesulfonate (CAS RN 68076-37-9) to afford the title compound (3.98 g, 11.2 mmol, 82%). ¹ H NMR (300 MHz, CDCl ₃ ) δ 7.85 (dd, J = 7.8, 1.8 Hz, 1H), 7.56 – 7.20 (m, 6H), 7.06 – 6.87 (m, 2H), 6.54 (s, 1H, NHCbz), 5.11 (s, 2H, OCH2), 4.24 (q, J = 7.1 Hz, 2H, OCH2CH3), 4.13 (t, J = 5.5 Hz, 2H, OCH2), 3.57 – 3.40 (m, 2H, CH2NHCbz), 2.06 (p, J = 5.6 Hz, 2H, -CH2-), 1.29 (t, J = 7.1 Hz, 3H, OCH2CH3). ¹³ C NMR (75 MHz, CDCl3) δ 166.0, 158.7, 157.0 (C=O CO2Et, C=O Cbz, C _Ar -O), 137.1, 133.9, 132.0, 128.4, 128.0, 127.9, 120.4, 119.7, 112.7, 68.2 (OCH2), 66.5 (OCH2), 61.0 (OCH2), 39.9 (CH2NHCbz), 29.1 (-CH2-), 14.4 (CH3). LC- HRMS (ESI) calc. for C ₂₀ H ₂₃ NO ₅ Na [M+Na]+: 380.1468; found: 380.1474. Step e Benzyl (3-(2-(hydroxymethyl)phenoxy)propyl)carbamate In analogy to the procedure described in Example 1 e), Ethyl 2-(3- (((benzyloxy)carbonyl)amino)propoxy)benzoate was reacted to afford the title compound (2.35 g, 7.45 mmol, 98%). ¹ H NMR (300 MHz, CDCl3) δ 7.39 – 7.19 (m, 7H), 6.94 (td, J = 7.4, 1.1 Hz, 1H), 6.83 (d, J = 8.1 Hz, 1H), 5.08 (s, 2H, -OCH2-), 4.66 (s, 2H, -OCH2-), 4.03 (td, J = 5.9, 1.7 Hz, 2H, -OCH ₂ CH ₂ CH ₂ NHCbz), 3.40 (t, J = 6.3 Hz, 2H, - OCH2CH2CH2NHCbz), 1.98 (p, J = 5.9 Hz, 2H, -OCH2CH2CH2NHCbz). ¹³ C NMR (75 MHz, CDCl3) δ 156.7, 156.6 (C=O Cbz, CAr-O), 136.6, 129.3, 129.0, 128.5, 128.09, 128.04, 120.7, 111.0 (C-Ar), 66.7 (OCH ₂ ), 65.7 (OCH ₂ ), 61.5 (OCH ₂ ), 38.6 (CH ₂ -NHCbz), 29.4 (- CH ₂ - linker). LC-HRMS (ESI) calc. for C ₁₈ H ₂₁ NO ₄ Na [M+Na] ⁺ : 338.1363; found: 338.1353. Step f Benzyl (3-(2-(bromomethyl)phenoxy)propyl)carbamate In analogy to the procedure described in Example 1 f), benzyl (3-(2- (hydroxymethyl)phenoxy)propyl)carbamate was reacted to afford the title compound (2.00 g, 5.29 mmol, 80%). ¹ H NMR (300 MHz, CDCl ₃ ) δ 7.45 – 7.18 (m, 7H), 6.98 – 6.79 (m, 2H), 5.11 (s, 2H, OCH2), 4.54 (s, 2H, CH2-Br), 4.10 (t, J = 5.8 Hz, 2H, , OCH2 linker), 3.49 (q, J = 6.4 Hz, 2H, CH2-NHCbz), 2.18 – 1.96 (m, 2H , -CH2- linker). ¹³ C NMR (75 MHz, CDCl ₃ ) δ 156.8, 156.7 (C=O Cbz, C _Ar -O), 136.7, 131.0, 130.8, 130.5, 130.4, 128.7, 128.2, 126.2, 125.9, 121.0, 111.77, 111.71 (C-Ar), 66.8 (-OCH ₂ -), 65.85 (-OCH ₂ -), 42.13 (-CH ₂ - NHCbz), 38.6 (CH2-Br), 29.53 (-CH2- linker). LC-HRMS (ESI) calc. for C18H21BrNO3 [M+H] ⁺ : 378.0699; found: 378.0700 Step g tert-Butyl 3-(((2-(3- (((benzyloxy)carbonyl)amino)propoxy)benzyl)oxy)methyl)azetid ine-1-carboxylate In analogy to the procedure described in Example 1 g), benzyl (3-(2- (bromomethyl)phenoxy)propyl)carbamate was reacted with tert-butyl 3- (hydroxymethyl)azetidine-1-carboxylate (CAS RN 142253-56-3) to afford the title compound (401 mg, 0.83 mmol, 59%). ¹ H NMR (300 MHz, CDCl3) δ 7.41 – 7.28 (m, 7H), 6.95 (td, J = 7.5, 1.1 Hz, 1H), 6.85 (d, J = 8.2 Hz, 1H), 5.46 (s, 1H, NHCbz), 5.10 (s, 2H, OCH ₂ ), 4.54 (s, 2H, OCH ₂ ), 4.05 (t, J = 5.8 Hz, 2H), 3.92 (t, J = 8.4 Hz, 2H), 3.67 – 3.51 (m, 4H), 3.43 (q, J = 6.1 Hz, 2H, CH ₂ NHCbz), 2.81 – 2.63 (m, 1H, CH azetidine), 2.02 (p, J = 6.0 Hz, 2H, CH2 linker), 1.42 (s, 9H, 3 x CH3 Boc). ¹³ C NMR (75 MHz, CDCl3) δ 156.7, 156.6, 156.5 (C=O Cbz, C=O Boc, C _Ar -O), 136.8, 129.6, 129.2, 128.6, 128.2, 126.4, 120.8, 111.4, 79.4 (C(CH ₃ ) ₃ Boc), 72.4 (OCH ₂ ), 68.7 (OCH ₂ ), 66.7 (OCH ₂ ), 66.4 (OCH ₂ ), 52.0 (2 x N-CH2- azetidine), 39.1 (CH2NHCbz), 29.6(CH azetidine), 28.5 (3 x CH3 Boc), 27.1 (- CH2- linker). LC-HRMS (ESI) calc. for C27H37N2O6 [M+H] ⁺ : 485.2646; found: 485.2646. BB9 tert-Butyl 3-(((2-((5- (((benzyloxy)carbonyl)amino)pentyl)oxy)benzyl)oxy)methyl)aze tidine-1-carboxylate Step d Ethyl 2-((5-(((benzyloxy)carbonyl)amino)pentyl)oxy)benzoate In analogy to the procedure described in Example 1g), ethyl salicylate (CAS RN 118-61-6) was reacted with 5-(((benzyloxy)carbonyl)amino)pentyl 4-methylbenzenesulfonate (CAS RN 93066-51-4) to afford the title compound (1.0 g, 2.59 mmol, 89%). ¹ H NMR (300 MHz, CDCl ₃ ) δ 7.77 (dd, J = 7.7, 1.8 Hz, 1H), 7.52 – 7.28 (m, 6H), 7.04 – 6.84 (m, 2H), 5.09 (s, 2H, O-CH2), 4.31 (q, J = 7.1 Hz, 2H, O-CH2-CH3), 4.02 (t, J = 6.2 Hz, 2H, O-CH2), 3.23 (m, 2H, -CH ₂ -NHCbz), 1.84 (p, J = 6.5 Hz, 2H, -CH ₂ - alkane), 1.64 – 1.53 (m, 4H, 2 x - CH ₂ - alkane), 1.33 (t, J = 7.1 Hz, 3H, O-CH ₂ -CH ₃ ). ¹³ C NMR (75 MHz, CDCl ₃ ) δ 166.6, 158.6, 156.6 (C=O CO2Et, C=O Cbz, CAr-O), 136.8, 133.4, 131.66, 128.6, 128.22, 128.19, 120.8, 120.3, 113.2 (C-Ar), 68.5, 66.7, 60.9 (3 x O-CH2), 41.0 (-CH2-NHCbz), 31.1, 28.8, 23.2 (3 x CH ₂ alkane), 14.44 (O-CH ₂ CH ₃ ). LC-HRMS (ESI) calc. for C ₂₂ H ₂₇ NO ₅ Na [M+Na] ⁺ : 408.1781; found: 408.1798. Step e Benzyl (5-(2-(hydroxymethyl)phenoxy)pentyl)carbamate In analogy to the procedure described in Example 1 e), ethyl 2-((5- (((benzyloxy)carbonyl)amino)pentyl)oxy)benzoate was reacted to afford the title compound (737 mg, 2.15 mmol, 86%). ¹ H NMR (300 MHz, CDCl3) δ 7.41 – 7.19 (m, 7H), 6.93 (td, J = 7.4, 1.0 Hz, 1H), 5.10 (s, 2H, OCH ₂ ), 4.68 (s, 2H, OCH ₂ ), 4.01 (t, J = 6.3 Hz, 2H, OCH ₂ ), 3.23 (t, J = 6.6 Hz, 2H CH ₂ NHCbz), 1.84 (p, J = 6.5 Hz, 2H, -CH ₂ - alkane), 1.68 – 1.46 (m, 4H, 2 x -CH2- alkane). ¹³ C NMR (75 MHz, CDCl3) δ 157.0, 156.6 (C=O Cbz, CAr-O), 136.7, 129.3, 129.1, 128.9, 128.7, 128.3, 128.3, 120.8, 111.2, 67.7 (OCH ₂ ), 66.8 (OCH ₂ ), 62.3 (CH ₂ OH), 41.0 (CH ₂ NHCbz), 29.9 (-CH ₂ - alkane), 27.1 (-CH ₂ - alkane), 23.5 (-CH ₂ - alkane). LC-HRMS (ESI) calc. for C20H25NO4Na [M+Na] ⁺ : 366.1676; found: 366.1691. Step f tert-Butyl 3-(((2-((5- (((benzyloxy)carbonyl)amino)pentyl)oxy)benzyl)oxy)methyl)aze tidine-1-carboxylate In analogy to the procedure described in Example 1 f), benzyl (5-(2- (hydroxymethyl)phenoxy)pentyl)carbamate was reacted with tert-butyl 3- (hydroxymethyl)azetidine-1-carboxylate (CAS RN 142253-56-3) to afford the title compound 67.6 mg, 0.132 mmol, 53%) was obtained. ¹ H NMR (600 MHz, CDCl3) δ 7.38 – 7.28 (m, 5H), 7.27 – 7.19 (m, 2H), 6.94 (t, J = 7.4 Hz, 1H), 6.84 (d, J = 8.3 Hz, 1H), 5.10 (s, 2H, OCH ₂ ), 4.97 (s, 1H, NHCbz), 4.56 (s, 2H, OCH ₂ ), 4.00 – 3.93 (m, 4H), 3.70 – 3.64 (m, 2H), 3.64 – 3.59 (m, 2H), 3.23 (q, J = 6.7 Hz, 2H, CH ₂ NHCbz), 2.82 – 2.73 (m, 1H, CH azetidine), 1.85 – 1.77 (m, 2H, CH2 linker), 1.63 – 1.48 (m, 4H, CH2 linker), 1.43 (s, 9H, 3 x CH3 Boc). ¹³ C NMR (151 MHz, CDCl3) δ 156.63, 156.58, 156.55 (C=O Boc, C=O Cbz, C _Ar -O), 136.8, 129.1, 128.9, 128.6, 128.21, 128.17, 126.7, 120.5, 111.2, 79.4 (C(CH ₃ ) ₃ Boc), 72.6, 68.2, 67.8, 66.7 (4 x OCH2), 52.0 (2 x NCH2 azetidine), 41.1 (CH2NHCbz), 29.8, 29.0, 28.8 (CH azetidine, 2 x CH2 linker), 28.5 (3 x CH3 Boc), 23.5 (CH2 linker). LC-HRMS (ESI) Calc for C29H40N2O6Na [M+Na]+: 535.2779; found: 537.2784 BB10 tert-Butyl 6-(2-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzylidene)-2- azaspiro[3.3]heptane-2-carboxylate Step i Synthesis of the building block: tert-butyl 6-((4,4,5,5-tetramethyl-1,3,2- dioxaborolan-2-yl)methylene)-2-azaspiro[3.3]heptane-2-carbox ylate In an oven-dried flask, tetramethylpiperidine (CAS RN 768-66-1,1.25 mL, 7.40 mmol) was dissolved in anhydrous THF (37.0 mL) and cooled to -78 °C under N2 atmosphere. A solution of nBuLi 2.5 M in THF (3.00 mL, 7.40 mmoL) was added dropwise, and the reaction was stirred at the same temperature for 30 min. Next, a 0.84 M solution of bis((pinacolato)boryl)methane (CAS RN 78782-17-9) in THF (8.83 mL, 7.40 mmol) was added dropwise. The reaction was stirred for 5 min and then a 0.20 M solution of ketone in anhydrous THF (18.5 mL, 3.70 mmol) was added dropwise over 5 min. The reaction mixture was slowly allowed to warm up to room temperature overnight. Upon completion, the reaction was opened to air and filtered through a silica plug eluting with Et2O. The mixture was concentrated under reduced pressure and purified by silica gel chromatography 0 to 20% EtOAc in cyclohexane with ELSD detection to afford the title compound in quantitative yield. LC-HRMS (ESI) calc. for C18H31BNO4 [M+H] ⁺ : 336.2340; found: 336.2342. Step d Benzyl (2-(2-bromophenoxy)ethyl)carbamate In analogy to the procedure described in Example 1 d), 2-bromophenol (CAS 95-56-7) was reacted with 2-(((benzyloxy)carbonyl)amino)ethyl 4-methylbenzenesulfonate (CAS RN 93407-96-6) to afford the title compound (985 mg, 2.81 mmol, 94%). ¹ H NMR (300 MHz, CDCl3) δ 7.47 (dd, J = 7.9, 1.6 Hz, 1H), 7.33 – 7.13 (m, 6H), 6.87 – 6.73 (m, 2H), 5.31 (s, 1H, NHCbz), 5.06 (s, 2H, OCH2), 4.03 (t, J = 5.0 Hz, 2H, OCH2), 3.59 (q, J = 5.4 Hz, 2H, CH ₂ NHCbz). ¹³ C NMR (75 MHz, CDCl ₃ ) δ 156.6, 154.9 (C=O Cbz, C _Ar -O), 136.5, 133.5, 128.7, 128.7, 128.29, 128.26, 122.6, 113.7, 112.5, 68.5 (OCH2), 67.0 (OCH2), 40.6 (CH2NHCbz). LC-HRMS (ESI) Calc for C16H16BrNO3Na [M+Na]+: 372.0206; found: 372.0209. Step h tert-Butyl 6-(2-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzylidene)-2- azaspiro[3.3]heptane-2-carboxylate In a closed vial under nitrogen atmosphere, tert-butyl 6-((4,4,5,5-tetramethyl-1,3,2- dioxaborolan-2-yl)methylene)-2-azaspiro[3.3]heptane-2-carbox ylate (117 mg, 0.35 mmol), Benzyl (2-(2-bromophenoxy)ethyl)carbamate (123 mg, 0.35 mmol) and Na2CO3 (74.2 mg, 0.70 mmol) were suspended in a dioxane/water 3:1 mixture (2.30 mL) previously purged by bubbling N ₂ with sonication. The mixture was purged with N ₂ bubbling for 10 min. Then, Pd(dppf)Cl2 (CAS RN 72287-26-4) was added and the mixture was purged for additional 15 min. The reaction was warmed up to 55 °C and stirred overnight at this temperature. The reaction was then diluted with DCM (15 mL), extracted with aq. sat. NaHCO ₃ (20 mL) and washed with brine (20 mL). The organic layer was dried over MgSO4, concentrated under reduced pressure and purified by silica gel chromatography 0 to 60% EtOAc in cyclohexane to afford the title compound (97.0 mg, 0.20 mmol, 58%). LC-HRMS (ESI) calc. for C28H34N2O5Na [M+Na]+: 501.2360; found: 501.2388. BB11 tert-Butyl 6-(3-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzylidene)-2- azaspiro[3.3]heptane-2-carboxylate Step d Benzyl (2-(3-bromophenoxy)ethyl)carbamate In analogy to the procedure described for BB10, step d), 3-Bromophenol (CAS RN 591-20- 8) was reacted with 2-(((benzyloxy)carbonyl)amino)ethyl 4-methylbenzenesulfonate (CAS RN 93407-96-6) to afford the title compound (366mg, 0.69mmol, 69%). LC-MS [M+Na] ⁺ : 372.0. Step h tert-Butyl 6-(3-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzylidene)-2- azaspiro[3.3]heptane-2-carboxylate In analogy to the procedure described for BB10, step h), Benzyl (2-(3- bromophenoxy)ethyl)carbamate was reacted with tert-butyl 6-((4,4,5,5-tetramethyl-1,3,2- dioxaborolan-2-yl)methylene)-2-azaspiro[3.3]heptane-2-carbox ylate to afford the title compound (181mg, 0.38mmol, 63%). ¹ H NMR (300 MHz, CDCl ₃ ) δ 7.41 – 7.30 (m, 5H), 7.21 (t, J = 8.1 Hz, 1H), 6.83 – 6.60 (m, 3H), 6.11 (s, 1H), 5.22 (s, 1H), 5.11 (s, 2H), 4.08 – 3.90 (m, 6H), 3.60 (d, J = 5.5 Hz, 2H), 3.20 (s, 2H), 3.04 (s, 2H), 1.42 (s, 9H). LC-MS (ESI): [M+H] ⁺ : 479.2. BB12 tert-Butyl 6-(2-((5-(((benzyloxy)carbonyl)amino)pentyl)oxy)benzylidene) -2- azaspiro[3.3]heptane-2-carboxylate Step d Benzyl (5-(2-bromophenoxy)pentyl)carbamate In analogy to the procedure described for BB10, step d), 3-Bromophenol (CAS RN 591-20- 8) was reacted with 5-(((benzyloxy)carbonyl)amino)pentyl 4-methylbenzenesulfonate (CAS RN 93066-51-4) to afford the title compound (403 mg, 1.03 mmol, 51%). ¹ H NMR (300 MHz, CDCl ₃ ) δ 7.52 (dd, J = 7.9, 1.6 Hz, 1H), 7.39 – 7.20 (m, 6H), 6.94 – 6.71 (m, 2H), 5.10 (s, 2H, OCH2), 4.78 (s, 1H, NHCbz), 4.01 (t, J = 6.2 Hz, 2H, OCH2), 3.24 (q, J = 6.3 Hz, 2H, CH2NHCbz), 1.86 (t, J = 6.8 Hz, 2H, CH2 linker), 1.76 – 1.48 (m, 4H, 2 x CH2 linker). ¹³ C NMR (75 MHz, CDCl ₃ ) δ 156.4, 155.3 (C=O Cbz, C _Ar -O), 136.6, 133.3, 128.5, 128.4, 128.1, 121.8, 113.2, 112.3, 68.8 (OCH2), 66.7 (OCH2), 41.0 (CH2NHCbz), 29.7 (CH2 linker), 28.7 (CH2 linker), 23.3 (CH2 linker). LC-HRMS (ESI) calc. for C19H23BrNO3 [M+H] ⁺ : 392.0856; found: 392.0860. Step h tert-Butyl 6-(2-((5-(((benzyloxy)carbonyl)amino)pentyl)oxy)benzylidene) -2- azaspiro[3.3]heptane-2-carboxylate In analogy to the procedure described for BB10, step h), Benzyl (5-(2- bromophenoxy)pentyl)carbamate was reacted with tert-butyl 6-((4,4,5,5-tetramethyl-1,3,2- dioxaborolan-2-yl)methylene)-2-azaspiro[3.3]heptane-2-carbox ylate to afford the title compound (100 mg, 0.19 mmol, 25%). LC-HRMS (ESI) calc. for C ₃₁ H ₄₁ N ₂ O ₅ [M+H] ⁺ : 521.3010; found: 521.3000. BB 14 tert-Butyl (1R,5S)-6-(((2-(2-(((benzyloxy)carbonyl)amino)ethoxy)benzyl) oxy)methyl)- 3-azabicyclo[3.1.0]hexane-3-carboxylate In analogy to the procedure described in Example 1 g), benzyl (2-(2- (bromomethyl)phenoxy)ethyl)carbamate (see Example 1) was reacted with tert-butyl (1R,5S,6r)-6-(hydroxymethyl)-3-azabicyclo[3.1.0]hexane-3-car boxylate (CAS RN 827599- 21-3) to afford the title compound (32.3 mg, 0.069 mmol, 57%). ¹ H NMR (300 MHz, CDCl3) δ 7.40 – 7.20 (m, 7H), 6.96 (td, J = 7.5, 1.1 Hz, 1H), 6.85 (d, J = 8.3 Hz, 1H), 5.09 (s, 2H, - OCH ₂ -), 4.52 (s, 2H, -OCH ₂ -), 4.10 (t, J = 5.1 Hz, 2H), 3.65 – 3.39 (m, 5H), 3.36 – 3.19 (m, 3H), 1.49 – 1.32 (m, 11H, 3 x CH3 Boc, 2 x CH fused cycle), 0.98 – 0.87 (m, 1H, CH propyl cycle). ¹³ C NMR (75 MHz, CDCl ₃ ) δ 156.57, 156.53, 155.0 (C=O Cbz, C=O Boc, C _Ar -O), 136.6, 129.8, 129.2, 128.6, 128.30, 128.25, 127.0, 121.2, 112.2 (C-Ar), 79.4, 71.7, 68.0, 67.6, 66.9, 48.1 (CH cyclopropyl), 40.7 (CH2-NHCbz), 28.6 (3 x CH3 Boc), 27.0, 22.4 (CH fused cycle). LC-HRMS (ESI) calc. for C28H37N2O6 [M+H] ⁺ : 497.2646; found: 497.2658. BB16 tert-Butyl 3-(3-(ethoxycarbonyl)phenoxy)azetidine-1-carboxylate In analogy to the procedure described in Example 39 d), ethyl 3-hydroxy benzoate (CAS RN 7781-98-8) was reacted with tert-butyl 3-iodoazetidine-1-carboxylate (CAS RN 254454-54-1) to afford the title compound. LC-MS (ESI) [M+Na] ⁺ : 344.1. BB17 tert-Butyl 3-((2-(ethoxycarbonyl)phenoxy)methyl)azetidine-1-carboxylate In analogy to the procedure described in Example 39 d), ethyl 3-hydroxy benzoate (CAS RN 7781-98-8) was reacted with tert-butyl 3-(bromomethyl)azetidine-1-carboxylate (CAS RN 253176-93-1) to afford the title compound. LC-MS (ESI) [M+Na] ⁺ : 358.1.