CHIRAL PHOSPHORAMIDITE AUXILIARIES AND METHODS OF THEIR USE

Field of the Invention

The invention relates to chiral auxiliaries and reagents useful for diastereoselective syntheses of P- stereogenic phosphites, phosphates, and phosphorothioates. The invention also relates to the preparation of oligonucleotides and methods of making chiral reagents.

Background

Oligonucleotides including phosphorothioate phosphodiesters have two possible oligonucleotide diastereomers for each P-stereogenic phosphorothioate. Many oligonucleotide therapeutics include multiple P-stereogenic phosphorothioates and thus have 2 ⁿ possible diastereomers, where n is the number of P-stereogenic phosphorothioates. For example, an oligonucleotide containing six

phosphorothioate phosphodiesters has 64 possible different diastereomers, which collectively can form over 10 ¹⁹ different diastereomeric mixtures. Separation of oligonucleotide diastereomers is impractical, in view of the material losses in the form of other diastereomers and the complexity of method development for oligonucleotide diastereomer separation. Accordingly, synthesis of oligonucleotides including P- stereogenic phosphorothioates requires development of reagents and methods for stereoselective introduction of P-stereogenic phosphorothioates. The currently available chiral reagents typically require lengthy synthetic routes. New reagents and methods for the synthesis of oligonucleotides including stereochemical^ enriched P-stereogenic phosphorothioates are needed.

Summary of the Invention

In general, the present invention provides P-stereogenic groups, compounds containing them, and methods for diastereoselective synthesis of, e.g., oligonucleotides including stereochemical^ enriched internucleoside phosphorothioates.

In one aspect, the invention provides a P-stereogenic group of formula (IA), (IB), (IC), or (ID):

(IA) (IB) (IC) (ID) where

is a single carbon-carbon bond or a double carbon-carbon bond;

each of R ¹ and R ² is independently an optionally substituted C1-6 alkyl or optionally substituted Ce- io aryl, or R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring; and

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted

Ce-10 aryl. In some embodiments, the P-stereogenic group is of formula (IA) or (IB). In certain embodiments, R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8- membered ring (e.g., an optionally substituted 5- to 8-membered carbocyclic ring (e.g., optionally substituted 5- to 8-membered ring is an optionally substituted 6-membered carbocyclic ring)).

In particular embodiments, the P-stereogenic group is of the following structure:

(ΙΙΑ') (ΙΙΒ')

In further embodiments, R ³ is H. In yet further embodiments, R ⁴ is H. In still further embodiments, R ³ and R ⁴ are each H.

In certain embodiments, the P-stereogenic group is of formula (MA), (MB), (ΙΙΑ'), or (MB'). In another aspect the invention provides a compound of formula (IIIA), (IIIB), (IMC), or (MID):

(IIIA) (IIIB) (MIC) (MID) where

is a single carbon-carbon bond or a double carbon-carbon bond;

A is an optionally substituted C1-12 alkyl, optionally substituted C3-10 cycloalkyl, optionally substituted C3-10 cycloalkyl-Ci-6-alkyl, optionally substituted C1-9 heterocyclyl, optionally substituted C1-9 heterocyclyl-Ci-6-alkyl, sugar analogue, nucleoside, nucleotide, or oligonucleotide;

each of R ¹ and R ² is independently an optionally substituted C1-6 alkyl or optionally substituted C6 10 aryl, or R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring; and

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted C6-10 aryl. In some embodiments, the compound is of formula (IMA) or (1MB).

In certain embodiments, R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring (e.g., optionally substituted 5- to 8-membered carbocyclic ring (e.g., optionally substituted 6-membered carbocyclic ring)).

In particular e

(IVA) (IVB) (IVC) (IVD)

(IVA') (IVB')

In further embodiments, R ³ is H. In yet further embodiments, R ⁴ is H. In still further embodiments, R ³ and R ⁴ are each H.

In other embodiments, the compound is of formula (IVA), (IVB), (IVA'), or (IVB').

In yet another aspect, the invention provides a nucleoside phosphoramidite including a sugar bonded to a nucleobase and to a phosphoramidite of the following structure:

where

is a single carbon-carbon bond or a double carbon-carbon bond;

each of R ¹ and R ² is independently an optionally substituted C1-6 alkyl or optionally substituted Ce- io aryl, or R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring; and

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted Ce-10 aryl. In some embodiments, the nucleoside phosphoramidite includes a phosphoramidite of formula (VA) or (VB).

In certain embodiments, the nucleoside phosphoramidite is of the following structure:

(VIC) (VID)

where

B ¹ is a nucleobase;

Y ¹ is H or C1-6 alkyl;

R ⁵ is H, O-protected hydroxyl, optionally substituted C1-6 alkoxy, or halogen; and

R ⁶ is a hydroxyl protecting group.

In particular embodiments, the nucleoside phosphoramidite is of formula (VIA) or (VIB).

In further embodiments, R ⁵ is hydrogen, halogen, or optionally substituted C1-6 alkoxy. In yet further embodiments, R ⁵ is hydrogen, fluoro, or methoxy. In still further embodiments, R ⁶ is dimethoxytrityl.

In some embodiments, R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring (e.g., optionally substituted 5- to 8-membered carbocyclic ring (e.g., optionally substituted 6-membered carbocyclic ring)).

(VIIA) (VI IB) (VIIC) (VIID)

(VIIA") (VIIB")

In further embodiments, R ³ is H. In yet further embodiments, R ⁴ is H. In still further embodiments, R ³ and R ⁴ are each H.

In still another aspect, the invention provides a compound of formula:

(VINA) (VIIIB) (VIIIC) (VIIID) where

is a single carbon-carbon bond or a double carbon-carbon bond;

X is a halogen or pseudohalogen;

each of R ¹ and R ² is independently an optionally substituted C1-6 alkyl or optionally substituted Ce- io aryl, or R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring; and

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted Ce-10 aryl.

In certain embodiments, the compound is of formula (VINA) or (VIIIB).

In some embodiments, R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring (e.g., optionally substituted 5- to 8-member carbocyclic ring (e.g., optionally substituted 6-member carbocyclic ring)).

In particular embodiments, the compound is of the following structure:

(IXA) (IXB) (IXC) (IXD)

(ΙΧΑ') (ΙΧΒ')

In some embodiments, the compound is of formula (IXA), (IXB), (ΙΧΑ'), or (ΙΧΒ').

In further embodiments, R ³ is H. In yet further embodiments, R ⁴ is H. In still further embodiments, R ³ and R ⁴ are each H.

In a further aspect, the invention provides a method of preparing a composition containing an oligonucleotide including a stereochemically enriched internucleoside phosphorothioate by (i) reacting the nucleoside phosphoramidite disclosed herein with a coupling activator and a nucleoside including a 5'- hydroxyl or an oligonucleotide including a 5'-hydroxyl, (ii) reacting with an electrophilic source of acyl, and (iii) reacting with a sulfurizing agent to produce the oligonucleotide containing a stereochemically enriched internucleoside phosphorothioate triester.

In some embodiments, the method further includes converting the phosphorothioate triester into a phosphorothioate diester by reacting the phosphorothioate triester with an aqueous base.

In particular embodiments, the coupling activator is 5-(benzylthio)-1 H-tetrazole (BTT), N- (phenyl)imidazolium trifluoromethanesulfonate (PhlMT), or N-(cyanomethyl)pyrrolidinium

trifluoromethanesulfonate (CMPT). In certain embodiments, the coupling activator is CMPT.

In further embodiments, the nucleoside is a 2'-deoxyribonucleoside. In yet further embodiments, the electrophilic source of acyl is an acid anhydride (e.g., acetic anhydride or trifluoroacetic anhydride). In still further embodiments, the sulfurizing agent is 3-((/V,/V-dimethylaminomethylidene)amino)-3H-1 ,2,4- dithiazole-5-thione (DDTT).

In yet further aspect, the invention provides a method of preparing the nucleoside phosphoramidite including a sugar bonded to a nucleobase and phosphoramidite of the following structure:

(VA) (VB) (VC) (VD) where

— is a single carbon-carbon bond or a double carbon-carbon bond; each of R ¹ and R ² is independently an optionally substituted C1-6 alkyl or optionally substituted Οβ- io aryl, or R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring; and

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted C6-io aryl;

by reacting a sugar bonded to a nucleobase with a compound of formula (VIIIA), (VIIIB), (VIIIC), or (VIIID):

(VIIIA) (VIIIB) (VIIIC) (VIIID)

where

X is a halogen or pseudohalogen.

In particular embodiments, the nucleoside phosphoramidite is of formula (VA) or (VB), and a sugar bonded to a nucleobase is reacted with a compound of formula (VIIIA) or (VIIIB).

In a further aspect, the invention provides an oligonucleotide (e.g., an oligonucleotide having a total of 2- 100 nucleosides (e.g., 2 to 50 or 2 to 35) including one or more (e.g., 1 to 6, 1 to 5, 1 to 4, 1 to 3, 1 to 2, or 1 ) internucleoside groups independently selected from the group consisting of linkers of formula (XIA) and (XIB):

(XIA) (XIB)

where

is a single carbon-carbon bond or a double carbon-carbon bond;

each of R ¹ and R ² is independently an optionally substituted C1-6 alkyl or optionally substituted Ce-10 aryl, or R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring;

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted Ce-10 aryl; and

R ⁷ is acyl (e.g., alkanoyl). In certain embodiments, R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring (e.g., optionally substituted 5- to 8-membered carbocyclic ring (e.g., optionally substituted 6-membered carbocyclic ring)).

In some embodiments, the one or more (e.g., 1 to 6, 1 to 5, 1 to 4, 1 to 3, 1 to 2, or 1 ) internucleoside groups are sele (XMIB), (XMIA ), and (XMIB ) :

(XMIA) (XMIB) (XMIA ) (XMIB ) where

is a single carbon-carbon bond or a double carbon-carbon bond;

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted Ce-10 aryl; and

R ⁷ is acyl (e.g., alkanoyl).

In further embodiments, R ³ is H. In yet further embodiments, R ⁴ is H. In still further embodiments, R ³ and R ⁴ are each H.

In a yet further aspect, the invention provides an oligonucleotide (e.g., an oligonucleotide having a total of 2-100 nucleosides (e.g., 2 to 50 or 2 to 35) including one or more (e.g., 1 to 6, 1 to 5, 1 to 4, 1 to 3, 1 to 2, or 1 ) internucleoside groups independently selected from the group consisting of linkers of formula (XIIA) and (XIIB):

(XIIA) (XIIB)

where

is a single carbon-carbon bond or a double carbon-carbon bond;

each of R ¹ and R ² is independently an optionally substituted C1-6 alkyl or optionally substituted Ce-10 aryl, or R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring; each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted Ce-10 aryl; and

R ⁷ is acyl (e.g., alkanoyl). In certain embodiments, R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring (e.g., optionally substituted 5- to 8-membered carbocyclic ring (e.g., optionally substituted 6-membered carbocyclic ring)).

In some embodiments, the one or more (e.g., 1 to 6, 1 to 5, 1 to 4, 1 to 3, 1 to 2, or 1 ) internucleoside groups are sele VB), (XIVA'), and (XIVB'):

, and

(XIVA) (XIVB) (XIVA') (XIVB') where

is a single carbon-carbon bond or a double carbon-carbon bond;

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted

Ce-10 aryl; and

R ⁷ is acyl (e.g., alkanoyl).

In further embodiments, R ³ is H. In yet further embodiments, R ⁴ is H. In still further embodiments, R ³ and R ⁴ are each H.

Definitions

The term "abasic spacer," as used herein, refers to internucleoside, abasic spacers known in the art, e.g., those described in WO 2018/035380. For example, an abasic spacer may be a group of formula (Χ'):

(X)

where

each of R ^A1 and R ^A2 is independently H, -OR ^A4 , or— N(R ^A4 )(R ^A5 ); where R ^A4 is optionally substituted C1-16 alkyl, optionally substituted C2-16 heteroalkyl, or a protecting group, and R ^A5 is H optionally substituted C1-16 alkyl, optionally substituted C2-16 heteroalkyl, or a protecting group; and each of ml , m2, m3, and m4 is independently an integer from 0 to 1 1 , provided that the quaternary carbon in the structure above is bonded to 0 or 1 atoms other than carbon and hydrogen, and provided that the sum of ml , m2, m3 and m4 is 1 1 or less. The term "about," as used herein, represents a value that is ±10% of the recited value.

The term "acyl," as used herein, represents a group of formula -C(0)-R ¹ , where R ¹ is H, alkyl, aryl, or heteroaryl. Acyl may be optionally substituted as defined for the group present as R ¹ in acyl. Acyl, in which R ¹ is alkyl (e.g., optionally substituted alkyl), may be referred to as an alkanoyl. Acyl, in which R ¹ is aryl (e.g., optionally substituted aryl), may be referred to as an aryloyl. Acyl, in which R ¹ is heteroaryl (e.g., optionally substituted heteroaryl), may be referred to as an heteroaryloyl.

The term "acyloxy," as used herein, represents a group of formula -OR, where R is acyl. Acyloxy may be optionally substituted as defined for acyl. Acyloxy, in which R is alkanoyl (e.g., optionally substituted alkanoyl), may be referred to as an alkanoyloxy. Acyl, in which R is aryloyl (e.g., optionally substituted aryloyl), may be referred to as an aryloyloxy. Acyl, in which R is heteroaryloyl (e.g., optionally substituted heteroaryloyl), may be referred to as an heteroaryloyloxy.

The term "alkanoylamino," as used herein, represents a group of formula -NHR, where R is alkanoyl.

The term "alkenyl," as used herein, represents acyclic monovalent straight or branched chain

hydrocarbon groups of containing one, two, or three carbon-carbon double bonds. An unsubstituted alkenyl includes 2 to 16 carbon atoms. Non-limiting examples of the alkenyl groups include ethenyl, prop- 1 -enyl, prop-2-enyl, 1 -methylethenyl, but-1 -enyl, but-2-enyl, but-3-enyl, 1 -methylprop-1 -enyl, 2- methylprop-1 -enyl, and 1 -methylprop-2-enyl. Alkenyl groups may be optionally substituted with 1 , 2, 3, or 4 substituent groups selected, independently, from the group consisting of aryl, cycloalkyl, heterocyclyl (e.g., heteroaryl), as defined herein, and the substituent groups described for alkyl.

The term "alkenylene," as used herein, refers to a straight or branched chain alkenyl group with one hydrogen removed, thereby rendering this group divalent. The valency of alkenylene defined herein does not include the optional substituents. Non-limiting examples of the alkenylene groups include ethen-1 ,1 - diyl; ethen-1 ,2-diyl; prop-1 -en-1 ,1 -diyl, prop-2-en-1 ,1 -diyl ; prop-1 -en-1 ,2-diyl, prop-1 -en-1 ,3-diyl ; prop-2- en-1 ,1 -diyl; prop-2-en-1 ,2-diyl; but-1 -en-1 ,1 -diyl ; but-1 -en-1 ,2-diyl; but-1 -en-1 ,3-diyl ; but-1 -en-1 ,4-diyl; but- 2-en-1 ,1 -diyl; but-2-en-1 ,2-diyl; but-2-en-1 ,3-diyl ; but-2-en-1 ,4-diyl ; but-2-en-2,3-diyl; but-3-en-1 ,1 -diyl; but-3-en-1 ,2-diyl; but-3-en-1 ,3-diyl ; but-3-en-2,3-diyl; buta-1 ,2-dien-1 ,1 -diyl; buta-1 ,2-dien-1 ,3-diyl; buta- 1 ,2-dien-1 ,4-diyl ; buta-1 ,3-dien-1 ,1 -diyl; buta-1 ,3-dien-1 ,2-diyl; buta-1 ,3-dien-1 ,3-diyl; buta-1 ,3-dien-1 ,4- diyl; buta-1 ,3-dien-2,3-diyl; buta-2,3-dien-1 ,1 -diyl; and buta-2,3-dien-1 ,2-diyl. The alkenylene group may be unsubstituted or substituted (e.g., optionally substituted alkenylene) as described for alkenyl groups. The term "alkenoxy," as used herein, represents a chemical substituent of formula -OR, where R is an alkenyl group, unless otherwise specified. An alkenyloxy group may be substituted or unsubstituted (e.g., optionally substituted alkenyloxy) as described herein for alkyl groups. The term "alkoxy," as used herein, represents a chemical substituent of formula -OR, where R is a C1-6 alkyl group, unless otherwise specified. In some embodiments, the alkyl group can be optionally substituted in the manner described for alkyl groups.

The term "alkoxycarbonyl," as used herein, represents a chemical substituent of formula -COOR, where R is alkyl. An alkoxycarbonyl group may be substituted or unsubstituted (e.g., optionally substituted alkoxycarbonyl) as described herein for alkyl groups.

The term "alkyl," as used herein, refers to an acyclic straight or branched chain saturated hydrocarbon group having from 1 to 16 carbons (when unsubstituted), unless otherwise specified. Alkyl groups are exemplified by methyl; ethyl; n- and iso-propyl; n-, sec-, iso- and tert-butyl; neopentyl, and the like, and may be optionally substituted with one, two, three, or, in the case of alkyl groups of two carbons or more, four substituents independently selected from the group consisting of: (1 ) alkoxy; (2) alkylsulfinyl; (3) amino; (4) arylalkoxy; (5) (arylalkyl)aza; (6) azido; (7) halo; (8) (heterocyclyl)oxy; (9) (heterocyclyl)aza; (10) hydroxy; (1 1 ) nitro; (12) oxo; (13) aryloxy; (14) sulfide; (15) thioalkoxy; (16) thiol; (17) aryl ; (18) - <X>2R ^A , where R ^A is selected from the group consisting of (a) alkyl, (b) aryl, (c) hydrogen, and (d) arylalkyi; (1 9) -C(0)NR ^B R ^c , where each of R ^B and R ^c is, independently, selected from the group consisting of (a) hydrogen, (b) alkyl, (c) aryl, and (d) arylalkyi; (20) -S02R ^D , where R ^D is selected from the group consisting of (a) alkyl, (b) aryl, and (c) arylalkyi ; (21 ) -S02NR ^E R ^F , where each of R ^E and R ^F is, independently, selected from the group consisting of (a) hydrogen, (b) alkyl, (c) aryl and (d) arylalkyi; (22) silyl; (23) cyano; and (24) -S(0)R ^H where R ^H is selected from the group consisting of (a) hydrogen, (b) alkyl, (c) aryl, and (d) arylalkyi. In some embodiments, each of these groups can be further substituted with unsubstituted substituents as described herein for each respective group.

The term "alkylamino," as used herein, refers to a group -N(R ^N1 )2, in which each R ^N1 is independently H or alkyl, provided that at least one R ^N1 is alkyl. Alkylamino may be optionally substituted; each alkyl in optionally substituted alkylamino is independently and optionally substituted as described for alkyl.

The term "alkylaminocarbonyl," as used herein, represents a chemical substituent of formula R-(CO)-, where R is alkylamino.

The term "alkylaminoalkylaminocarbonyl," as used herein, represents a chemical substituent of formula R ¹ -R ² -NH-(CO)-, where R ¹ is alkylamino, and R ² is alkylene.

The term "alkylene," as used herein, refers to a saturated divalent hydrocarbon group derived from a straight or branched chain saturated hydrocarbon by the removal of two hydrogen atoms. The valency of alkylene defined herein does not include the optional substituents. Non-limiting examples of the alkylene group include methylene, ethane-1 ,2-diyl, ethane-1 , 1 -diyl, propane-1 ,3-diyl, propane-1 ,2-diyl, propane-

1 .1 - diyl, propane-2,2-diyl, butane-1 ,4-diyl, butane-1 ,3-diyl, butane-1 ,2-diyl, butane-1 ,1 -diyl, and butane-

2.2- diyl, butane-2,3-diyl. The term "Cx- _y alkylene" represents alkylene groups having between x and y carbons. Exemplary values for x are 1 , 2, 3, 4, 5, and 6, and exemplary values for y are 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , and 12. In some embodiments, the alkylene can be optionally substituted with 1 , 2, 3, or 4 substituent groups as defined herein for an alkyl group. Similarly, the suffix "ene" designates a divalent radical of the corresponding monovalent radical as defined herein. For example, alkenylene, alkynylene, arylene, aryl alkylene, cycloalkylene, cycloalkyl alkylene, cycloalkenylene, heteroarylene, heteroaryl alkylene, heterocyclylene, and heterocyclyl alkylene are divalent forms of alkenyl, alkynyl, aryl, aryl alkyl, cycloalkyl, cycloalkyl alkyl cycloalkenyl, heteroaryl, heteroaryl alkyl, heterocyclyl, and heterocyclyl alkyl. For aryl alkylene, cycloalkyl alkylene, heteroaryl alkylene, and heterocyclyl alkylene, the two valences in the group may be located in the acyclic portion only or one in the cyclic portion and one in the acyclic portion. For example, the alkylene group of an aryl-Ci-alkylene or a heterocyclyl-Ci -alkylene can be further substituted with an oxo group to afford the respective aryloyl and (heterocyclyl)oyl substituent group.

The term "alkyleneoxy," as used herein, refers to a divalent group -R-0-, in which R is alkylene.

Alkylene in alkyleneoxy may be unsubstituted or substituted (e.g., optionally substituted alkyleneoxy) as described for alkyl.

The term "alkylsulfonyl," as used herein, refers to a group -SO2-R, where R is alkyl.

The term "alkylsulfonyloxy," as used herein, refers to a group -OR, where R is alkylsulfonyl. The term "alkynyl," as used herein, represents monovalent straight or branched chain hydrocarbon groups of from two to sixteen carbon atoms containing at least one carbon-carbon triple bond and is exemplified by ethynyl, 1 -propynyl, and the like. Alkynyl groups may be optionally substituted with 1 , 2, 3, or 4 substituent groups that are selected, independently, from aryl, alkenyl, cycloalkyl, and heterocyclyl (e.g., heteroaryl), as described herein, and the substituent groups described for alkyl.

The term "alkynylene," as used herein, refers to a straight-chain or branched-chain divalent substituent including one or two carbon-carbon triple bonds and containing only C and H when unsubstituted. An unsubstituted alkynylene contains from two to sixteen carbon atoms, unless otherwise specified. The valency of alkynylene defined herein does not include the optional substituents. Non-limiting examples of the alkenylene groups include ethyn-1 ,2-diyl; prop-1 -yn-1 ,3-diyl ; prop-2-yn-1 ,1 -diyl; but-1 -yn-1 ,3-diyl; but- 1 -yn-1 ,4-diyl; but-2-yn-1 ,1 -diyl; but-2-yn-1 ,4-diyl ; but-3-yn-1 ,1 -diyl; but-3-yn-1 ,2-diyl ; but-3-yn-2,2-diyl; and buta-1 ,3-diyn-1 ,4-diyl. The alkynylene group may be unsubstituted or substituted (e.g., optionally substituted alkynylene) as described for alkynyl groups. The term "amino," as used herein, represents -N(R ^N1 )2, where, if amino is unsubstituted, both R ^N1 are H; or, if amino is substituted, each R ^N1 is independently H, -OH, -NO2, -N(R ^N2 ) ₂ , -S0 ₂ OR ^N2 , -S0 ₂ R ^N2 , - SOR ^N2 , -COOR ^N2 , an /V-protecting group, alkyl, alkenyl, alkynyl, alkoxy, aryl, arylalkyi, aryloxy, cycloalkyl, cycloalkenyl, heteroalkyl, or heterocyclyl, provided that at least one R ^N1 is not H, and where each R ^N2 is independently H, alkyl, or aryl. Each of the substituents may itself be unsubstituted or substituted with unsubstituted substituent(s) defined herein for each respective group. In some embodiments, amino is unsubstituted amino (i.e., -NH2) or substituted amino (e.g., -NHR ^N1 ), where R ^N1 is independently -OH, - S0 ₂ OR ^N2 , -S0 ₂ R ^N2 , -SOR ^N2 , -COOR ^N2 , optionally substituted alkyl, or optionally substituted aryl, and each R ^N2 can be optionally substituted alkyl or optionally substituted aryl. In some embodiments, substituted amino may be alkylamino, in which the alkyl group is optionally substituted as described herein for alkyl. In further embodiments, substituted amino may be dialkylamino, in which the alkyl groups are optionally substituted as described herein for alkyl. In certain embodiments, an amino group is -NHR ^N1 , in which R ^N1 is optionally substituted alkyl. Non-limiting examples of -NHR ^N1 , in which R ^N1 is optionally substituted alkyl, include: optionally substituted alkylamino, a proteinogenic amino acid, a non- proteinogenic amino acid, a C1-6 alkyl ester of a proteinogenic amino acid, and a C1-6 alkyl ester of a non- proteinogenic amino acid.

The term "aminoalkyl," as used herein, represents a chemical substituent of formula -R'-R", where R' is alkylene, and R" is amino. Aminoalkyl may be optionally substituted as defined for each of the two portions. The term "aminoalkylaminocarbonyl," as used herein, represents a chemical substituent of formula R ¹ -R ² -NH-(CO)-, where R ¹ is amino, and R ² is alkylene.

The term "aryl," as used herein, represents a mono-, bicyclic, or multicyclic carbocyclic ring system having one, two, or three (e.g., one or two) aromatic rings and is exemplified by phenyl, naphthyl, 1 ,2- dihydronaphthyl, 1 ,2,3,4-tetrahydronaphthyl, fluorenyl, indanyl, indenyl, and the like, and may be optionally substituted with one, two, three, four, or five substituents independently selected from the group consisting of: (1 ) acyl ; (2) alkyl; (3) alkenyl; (4) alkynyl; (5) alkoxy; (6) alkylsulfinyl ; (7) aryl ; (8) amino; (9) arylalkyi; (1 0) azido; (1 1 ) cycloalkyl; (12) cycloalkylalkyl ; (13) cycloalkenyl ; (14) cycloalkenylalkyl; (15) halo; (16) heterocyclyl (e.g., heteroaryl); (17) (heterocyclyl)oxy; (1 8) (heterocyclyl)aza; (19) hydroxy; (20) nitro; (21 ) thioalkoxy; (22) -(CH2) _q C02R ^A , where q is an integer from zero to four, and R ^A is selected from the group consisting of (a) alkyl, (b) aryl, (c) hydrogen, and (d) arylalkyi; (23) -(CH2) _q CONR ^B R ^c , where q is an integer from zero to four and where R ^B and R ^c are independently selected from the group consisting of (a) hydrogen, (b) alkyl, (c) aryl, and (d) arylalkyi; (24) -(CH2) _q S02R ^D , where q is an integer from zero to four and where R ^D is selected from the group consisting of (a) alkyl, (b) aryl, and (c) arylalkyi; (25) - (CH2) _q S02NR ^E R ^F , where q is an integer from zero to four and where each of R ^E and R ^F is, independently, selected from the group consisting of (a) hydrogen, (b) alkyl, (c) aryl, and (d) arylalkyi; (26) thiol ; (27) aryloxy; (28) cycloalkoxy; (29) arylalkoxy; (30) heterocyclylalkyl (e.g., heteroarylalkyl); (31 ) silyl; (32) cyano; and (33) -S(0)R ^H where R ^H is selected from the group consisting of (a) hydrogen, (b) alkyl, (c) aryl, and (d) arylalkyi. An unsubstituted aryl includes 6 to 14 carbon atoms (e.g., 6 to 10 carbon atoms). In some embodiments, each of these groups can be substituted with unsubstituted substituents as described herein for each respective group. The term "aryl alkyl," as used herein, represents an alkyl group substituted with an aryl group. Each of the aryl and alkyl portions may be independently unsubstituted or substituted (e.g., optionally substituted aryl alkyl) as described for the individual groups.

The term "arylene," as used herein, refers to a divalent group that is aryl, as defined herein, in which one hydrogen atom is replaced with a valency. Arylene may be unsubstituted or substituted (e.g., optionally substituted arylene) as described for aryl. The term "arylcarbonyl," as used herein, refers to a group -(CO)-R, where R is aryl. Arylcarbonyl may be unsubstituted or substituted (e.g., optionally substituted arylcarbonyl) as described herein for aryl.

The term "aryloxy," as used herein, refers to a group -OR, where R is aryl. Aryloxy may be unsubstituted or substituted (e.g., optionally substituted aryloxy) as described herein for aryl.

The term "aryloxy-carbonyl," as used herein, refers to a group -COOR, where R is aryl. Aryloxycarbonyl may be unsubstituted or substituted (e.g., optionally substituted aryloxycarbonyl) as described herein for aryl. The term "arylsulfonate," as used herein, represents a group -S(0)2-R, where R is aryl. Arylsulfonate may be unsubstituted or substituted (e.g., optionally substituted arylsulfonate) as described herein for aryl.

The term "aza," as used herein, represents a divalent -N(R ^N1 )- group or a trivalent -N= group. The aza group may be unsubstituted, where R ^N1 is H or absent, or substituted, where R ^N1 is as defined for

"amino." Aza may also be referred to as "N," e.g., "optionally substituted N." Two aza groups may be connected to form "diaza."

The term "azido," as used herein, represents an N3 group.

The term "carbamoyl," as used herein, refers to a group of formula RCOO-, where R is amino.

The term "carbocyclic," as used herein, represents an optionally substituted C3-12 monocyclic, bicyclic, or tricyclic structure in which the rings, which may be aromatic or non-aromatic, are formed by carbon atoms. Carbocyclic structures include cycloalkyl, cycloalkenyl, and aryl groups.

The term "cycloalkenyl," as used herein, refers to a non-aromatic carbocyclic group having from three to ten carbons (e.g., a C3-C10 cycloalkylene), unless otherwise specified. Non-limiting examples of cycloalkenyl include cycloprop-1 -enyl, cycloprop-2-enyl, cyclobut-1 -enyl, cyclobut-1 -enyl, cyclobut-2-enyl, cyclopent-1 -enyl, cyclopent-2-enyl, cyclopent-3-enyl, norbornen-1 -yl, norbornen-2-yl, norbornen-5-yl, and norbornen-7-yl. The cycloalkenyl group may be unsubstituted or substituted (e.g., optionally substituted cycloalkenyl) as described for cycloalkyi.

The term "cycloalkenyl alkyl," as used herein, represents an alkyl group substituted with a cycloalkenyl group. Each of the cycloalkenyl and alkyl portions may be independently unsubstituted or substituted (e.g., optionally substituted cycloalkenyl alkyl) as described for the individual groups.

The term "cycloalkenylene," as used herein, refers to a divalent carbocyclic non-aromatic group having from three to ten carbons (e.g., C3-C10 cycloalkenylene), unless otherwise specified. Non-limiting examples of the cycloalkenylene include cycloprop-1 -en-1 ,2-diyl; cycloprop-2-en-1 ,1 -diyl; cycloprop-2-en- 1 ,2-diyl; cyclobut-1 -en-1 ,2-diyl; cyclobut-1 -en-1 ,3-diyl; cyclobut-1 -en-1 ,4-diyl ; cyclobut-2-en-1 ,1 -diyl; cyclobut-2-en-1 ,4-diyl; cyclopent-1 -en-1 ,2-diyl; cyclopent-1 -en-1 ,3-diyl ; cyclopent-1 -en-1 ,4-diyl; cyclopent- 1 -en-1 ,5-diyl; cyclopent-2-en-1 ,1 -diyl; cyclopent-2-en-1 ,4-diyl; cyclopent-2-en-1 ,5-diyl; cyclopent-3-en-1 ,1 - diyl;cyclopent-1 ,3-dien-1 ,2-diyl; cyclopent-1 ,3-dien-1 ,3-diyl ; cyclopent-1 ,3-dien-1 ,4-diyl; cyclopent-1 ,3- dien-1 ,5-diyl ; cyclopent-1 ,3-dien-5,5-diyl ; norbornadien-1 ,2-diyl ; norbornadien-1 ,3-diyl; norbornadien-1 ,4- diyl; norbornadien-1 ,7-diyl; norbornadien-2,3-diyl; norbornadien-2,5-diyl; norbornadien-2,6-diyl;

norbornadien-2,7-diyl ; and norbornadien-7,7-diyl. The cycloalkenylene may be unsubstituted or substituted (e.g., optionally substituted cycloalkenylene) as described for cycloalkyi. The term "cycloalkyi," as used herein, refers to a cyclic alkyl group having from three to ten carbons (e.g., a C3-C10 cycloalkyi), unless otherwise specified. Cycloalkyi groups may be monocyclic or bicyclic.

Bicyclic cycloalkyi groups may be of bicyclo[p.q.0]alkyl type, in which each of p and q is, independently, 1 , 2, 3, 4, 5, 6, or 7, provided that the sum of p and q is 2, 3, 4, 5, 6, 7, or 8. Alternatively, bicyclic cycloalkyi groups may include bridged cycloalkyi structures, e.g., bicyclo[p.q.r]alkyl, in which r is 1 , 2, or 3, each of p and q is, independently, 1 , 2, 3, 4, 5, or 6, provided that the sum of p, q, and r is 3, 4, 5, 6, 7, or 8. The cycloalkyi group may be a spirocyclic group, e.g., spiro[p.q]alkyl, in which each of p and q is,

independently, 2, 3, 4, 5, 6, or 7, provided that the sum of p and q is 4, 5, 6, 7, 8, or 9. Non-limiting examples of cycloalkyi include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, 1 - bicyclo[2.2.1 .]heptyl, 2-bicyclo[2.2.1 .Jheptyl, 5-bicyclo[2.2.1 .Jheptyl, 7-bicyclo[2.2.1 .Jheptyl, and decalinyl. The cycloalkyi group may be unsubstituted or substituted as defined herein (e.g., optionally substituted cycloalkyi). The cycloalkyi groups of this disclosure can be optionally substituted with: (1 ) acyl ; (2) alkyl; (3) alkenyl; (4) alkynyl; (5) alkoxy; (6) alkylsulfinyl; (7) aryl; (8) amino; (9) arylalkyl ; (10) azido; (1 1 ) cycloalkyi; (12) cycloalkylalkyl; (13) cycloalkenyl ; (14) cycloalkenylalkyl; (15) halo; (16) heterocyclyl (e.g., heteroaryl); (17) (heterocyclyl)oxy; (18) (heterocyclyl)aza; (1 9) hydroxy; (20) nitro; (21 ) thioalkoxy; (22) -(CH2) _q C02R ^A , where q is an integer from zero to four, and R ^A is selected from the group consisting of (a) alkyl, (b) aryl, (c) hydrogen, and (d) arylalkyl ; (23) -(CH2) _q CONR ^B R ^c , where q is an integer from zero to four and where R ^B and R ^c are independently selected from the group consisting of (a) hydrogen, (b) alkyl, (c) aryl, and (d) arylalkyl; (24) -(CH2) _q S02R ^D , where q is an integer from zero to four and where R ^D is selected from the group consisting of (a) alkyl, (b) aryl, and (c) arylalkyl; (25) -(CH2) _q S02NR ^E R ^F , where q is an integer from zero to four and where each of R ^E and R ^F is, independently, selected from the group consisting of (a) hydrogen, (b) alkyl, (c) aryl, and (d) arylalkyl; (26) thiol; (27) aryloxy; (28) cycloalkoxy; (29) arylalkoxy; (30) heterocyclylalkyl (e.g., heteroarylalkyl); (31 ) silyl; (32) cyano; and (33) -S(0)R ^H where R ^H is selected from the group consisting of (a) hydrogen, (b) alkyl, (c) aryl, and (d) arylalkyl. In some embodiments, each of these groups can be substituted with unsubstituted substituents as described herein for each respective group.

The term "cycloalkylene," as used herein, refers to a divalent group that is cycloalkyl, as defined herein, in which one hydrogen atom is replaced with a valency. Cycloalkylene may be unsubstituted or substituted (e.g., optionally substituted cycloalkylene) as described for cycloalkyl. The term "cycloalkyl alkyl," as used herein, represents an alkyl group substituted with a cycloalkyl group. Each of the cycloalkyl and alkyl portions may be independently unsubstituted or substituted (e.g., optionally substituted cycloalkyl alkyl) as described for the individual groups.

The term "dialkylamino," as used herein, represents a group -N(R ^N1 )2, in which each R ^N1 is independently alkyl. Dialkylamino may be optionally substituted; each alkyl in optionally substituted dialkylamino is independently and optionally substituted as described for alkyl.

The term "dialkylaminocarbonyl," as used herein, represents a chemical substituent of formula R-(CO)-, where R is dialkylamino.

The term "dialkylaminoalkylaminocarbonyl," as used herein, represents a chemical substituent of formula R ¹ -R ² -NH-(CO)-, where R ¹ is dialkylamino, and R ² is alkylene.

The term "halo," as used herein, represents a halogen selected from bromine, chlorine, iodine, and fluorine.

The term "haloalkyi," as used herein, represents an alkyl group, as defined herein, substituted by a halogen group (i.e., F, CI, Br, or I). A haloalkyi may be substituted with one, two, three, or, in the case of alkyl groups of two carbons or more, four halogens, or, when the halogen group is F, haloalkyi group can be perfluoroalkyl. In some embodiments, the haloalkyi group can be further optionally substituted with 1 , 2, 3, or 4 substituent groups as described herein for alkyl groups.

The term "heteroalkyl," as used herein refers to an alkyl, alkenyl, or alkynyl group interrupted once by one heteroatom; twice, each time, independently, by one heteroatom ; three times, each time, independently, by one heteroatom; or four times, each time, independently, by one heteroatom. Each heteroatom is, independently, O, N, or S. In some embodiments, the heteroatom is O or N. An unsubstituted CX Y heteroalkyl contains from X to Y carbon atoms as well as the heteroatoms as defined herein. The heteroalkyl group may be unsubstituted or substituted (e.g., optionally substituted heteroalkyl). When heteroalkyl is substituted and the substituent is bonded to the heteroatom, the substituent is selected according to the nature and valency of the heteroatom. Thus, the substituent, if present, bonded to the heteroatom, valency permitting, is selected from the group consisting of =0, -N(R ^N2 )2, -S020R ^N3 , - S02R ^N2 , -SOR ^N3 , -COOR ^N3 , an /V-protecting group, alkyl, alkenyl, alkynyl, aryl, cycloalkyl, cycloalkenyl, cycloalkynyl, heterocyclyl, or cyano, where each R ^N2 is independently H, alkyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, or heterocyclyl, and each R ^N3 is independently alkyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, or heterocyclyl. Each of these substituents may itself be unsubstituted or substituted with unsubstituted substituent(s) defined herein for each respective group. When heteroalkyl is substituted and the substituent is bonded to carbon, the substituent is selected from those described for alkyl, provided that the substituent on the carbon atom bonded to the heteroatom is not CI, Br, or I. It is understood that carbon atoms are found at the termini of a heteroalkyl group. The term "heteroaryl," as used herein, represents that subset of heterocyclyls, as defined herein, which include an aromatic ring system that contains at least one heteroatom. Thus, heteroaryls contain 4n+2 pi electrons within the mono- or multicyclic ring system. Heteroaryl can be unsubstituted or substituted (e.g., optionally substituted heteroaryl) with 1 , 2, 3, or 4 substituents groups as defined for heterocyclyl. The term "heteroarylcarbonyl," as used herein, refers to a group -(CO)-R, where R is heteroaryl.

Heteroarylcarbonyl may be unsubstituted or substituted (e.g., optionally substituted heteroarylcarbonyl) as described herein for heterocyclyl.

The term "heteroaryloxy," as used herein, refers to a group -OR, where R is heteroaryl. Heteroaryloxy may be unsubstituted or substituted (e.g., optionally substituted heteroaryloxy) as described herein for heterocyclyl.

The term "heteroaryloxy-carbonyl," as used herein, refers to a group -COOR, where R is heteroaryl. Heteroaryloxycarbonyl may be unsubstituted or substituted (e.g., optionally substituted

heteroaryloxycarbonyl) as described herein for heterocyclyl.

The term "heteroaryl alkyl," as used herein, represents an alkyl group substituted with a heteroaryl group. Thus, heteroaryl alkyl is a heterocyclyl alkyl group, in which the heterocyclyl includes at least one aromatic ring system including a heteroatom. Each of the heteroaryl and alkyl portions may be independently unsubstituted or substituted (e.g., optionally substituted heteroaryl alkyl) as described for the individual groups.

The term "heterocyclyl," as used herein, represents a 5-, 6-, or 7-membered ring or a fused ring system of two, three, or four rings, each of which is independently a 5-, 6-, or 7-membered ring, unless otherwise specified, provided that at least one of the rings contains one, two, three, or four heteroatoms independently selected from the group consisting of nitrogen, oxygen, and sulfur. The 5-membered ring has zero to two double bonds, and the 6- and 7-membered rings have zero to three double bonds. An unsubstituted heterocyclyl contains from one to twelve carbon atoms, unless specified otherwise. In some embodiments, an unsubstituted heterocyclyl contains at least two carbon atoms. In certain embodiments, an unsubstituted heterocyclyl contains up to nice carbon atoms. The fused "heterocyclyl" be a bridged multicyclic structure in which one or more carbons and/or heteroatoms bridges two non- adjacent members of a monocyclic ring, e.g., as found in a quinuclidinyl group. In some embodiments, the fused "heterocyclyl" includes bicyclic, tricyclic, and tetracyclic groups, in which at least one of the rings includes one or more heteroatoms as defined herein, and the remaining rings are carbocyclic rings, e.g., an aryl ring, a cyclohexane ring, a cyclohexene ring, a cyclopentane ring, a cyclopentene ring. Non- limiting examples of such fused heterocyclyls include indolyl, quinolyl, isoquinolyl, tetrahydroquinolyl, benzofuryl, benzothienyl, tropanes, and 1 ,2,3,5,8,8a-hexahydroindolizine. Non-limiting examples of heterocyclyls include pyrrolyl, pyrrolinyl, pyrrolidinyl, pyrazolyl, pyrazolinyl, pyrazolidinyl, imidazolyl, imidazolinyl, imidazolidinyl, pyridyl, piperidinyl, homopiperidinyl, pyrazinyl, piperazinyl, pyrimidinyl, pyridazinyl, oxazolyl, oxazolidinyl, isoxazolyl, isoxazolidiniyl, morpholinyl, thiomorpholinyl, thiazolyl, thiazolidinyl, isothiazolyl, isothiazolidinyl, indolyl, quinolinyl, isoquinolinyl, benzimidazolyl, benzothiazolyl, benzoxazolyl, furyl, thienyl, thiazolidinyl, isothiazolyl, isoindazoyl, triazolyl, tetrazolyl, oxadiazolyl, purinyl, thiadiazolyl (e.g., 1 ,3,4-thiadiazole), tetrahydrofuranyl, dihydrofuranyl, tetrahydrothienyl, dihydrothienyl, dihydroindolyl, tetrahydroquinolyl, tetrahydroisoquinolyl, pyranyl, dihydropyranyl, dithiazolyl, benzofuranyl, benzothienyl and the like. Still other exemplary heterocyclyls are: 2,3,4,5-tetrahydro-2-oxo-oxazolyl; 2,3- dihydro-2-oxo-1 H-imidazolyl; 2,3,4,5-tetrahydro-5-oxo-1 H-pyrazolyl (e.g., 2,3,4,5-tetrahydro-2-phenyl-5- oxo-1 H-pyrazolyl); 2,3, 4, 5-tetrahydro-2,4-dioxo-1 H-imidazolyl (e.g., 2,3,4, 5-tetrahydro-2,4-dioxo-5-methyl- 5-phenyl-1 H-imidazolyl) ; 2,3-dihydro-2-thioxo-1 ,3,4-oxadiazolyl (e.g., 2,3-dihydro-2-thioxo-5-phenyl-1 ,3,4- oxadiazolyl); 4, 5-dihydro-5-oxo-1 -/-triazolyl (e.g., 4,5-dihydro-3-methyl-4-amino 5-oxo-1 /-/-triazolyl);

1 ,2,3,4-tetrahydro-2,4-dioxopyridinyl (e.g., 1 ,2,3,4-tetrahydro-2,4-dioxo-3,3-diethylpyridinyl); 2,6-dioxo- piperidinyl (e.g., 2,6-dioxo-3-ethyl-3-phenylpiperidinyl) ; 1 ,6-dihydro-6-oxopyridiminyl; 1 ,6-dihydro-4- oxopyrimidinyl (e.g., 2-(methylthio)-1 ,6-dihydro-4-oxo-5-methylpyrimidin-1 -yl); 1 ,2,3,4-tetrahydro-2,4- dioxopyrimidinyl (e.g., 1 ,2,3,4-tetrahydro-2,4-dioxo-3-ethylpyrimidinyl); 1 ,6-dihydro-6-oxo-pyridazinyl (e.g., 1 ,6-dihydro-6-oxo-3-ethylpyridazinyl); 1 ,6-dihydro-6-oxo-1 ,2,4-triazinyl (e.g., 1 ,6-dihydro-5-isopropyl-6- oxo-1 ,2,4-triazinyl) ; 2,3-dihydro-2-oxo-1 /--indolyl (e.g., 3,3-dimethyl-2,3-dihydro-2-oxo-1 /--indolyl and 2,3- dihydro-2-oxo-3,3'-spiropropane-1 /- -indol-1 -yl) ; 1 ,3-dihydro-1 -oxo-2/-/-iso-indolyl ; 1 ,3-dihydro-1 ,3-dioxo- 2/-/-iso-indolyl; 1 /-/-benzopyrazolyl (e.g., l -(ethoxycarbonyl)- 1 /-/-benzopyrazolyl) ; 2,3-dihydro-2-oxo-1 H- benzimidazolyl (e.g., 3-ethyl-2,3-dihydro-2-oxo-1 /-/-benzimidazolyl); 2,3-dihydro-2-oxo-benzoxazolyl (e.g., 5-chloro-2,3-dihydro-2-oxo-benzoxazolyl); 2,3-dihydro-2-oxo-benzoxazolyl; 2-oxo-2H-benzopyranyl ; 1 ,4- benzodioxanyl; 1 ,3-benzodioxanyl ; 2,3-dihydro-3-oxo,4/-/-1 ,3-benzothiazinyl; 3,4-dihydro-4-oxo-3/-/- quinazolinyl (e.g., 2-methyl-3,4-dihydro-4-oxo-3/-/-quinazolinyl); 1 ,2,3,4-tetrahydro-2,4-dioxo-3/-/- quinazolyl (e.g., 1 -ethyl-1 ,2,3,4-tetrahydro-2,4-dioxo-3f/-quinazolyl); 1 ,2,3,6-tetrahydro-2,6-dioxo-7/ purinyl (e.g., 1 ,2,3,6-tetrahydro-1 ,3-dimethyl-2,6-dioxo-7 /-/ -purinyl); 1 ,2,3,6-tetrahydro-2,6-dioxo-1 H - purinyl (e.g., 1 ,2,3,6-tetrahydro-3,7-dimethyl-2,6-dioxo-1 /-/ -purinyl); 2-oxobenz[c,c |indolyl ; 1 ,1 -dioxo-2H- naphth[1 ,8-c,c |isothiazolyl ; and 1 ,8-naphthylenedicarboxamido. Heterocyclic groups also include groups of the fo

F' is selected from the group consisting of -CH2-, -CH2O- and -0-, and G' is selected from the group consisting of -C(O)- and -(C(R')(R")) _V -, where each of FT and R" is, independently, selected from the group consisting of hydrogen or alkyl of one to four carbon atoms, and v is one to three and includes groups, such as 1 ,3-benzodioxolyl, 1 ,4-benzodioxanyl, and the like. Any of the heterocyclyl groups mentioned herein may be optionally substituted with one, two, three, four, or five substituents independently selected from the group consisting of: (1 ) acyl; (2) alkyl; (3) alkenyl; (4) alkynyl ; (5) alkoxy; (6) alkylsulfinyl; (7) aryl; (8) amino; (9) arylalkyl; (10) azido; (1 1 ) cycloalkyl ; (12) cycloalkylalkyl; (13) cycloalkenyl; (14) cycloalkenylalkyl; (15) halo; (1 6) heterocyclyl (e.g., heteroaryl); (17) (heterocyclyl)oxy; (18) (heterocyclyl)aza; (19) hydroxy; (20) oxo; (21 ) nitro; (22) sulfide; (23) thioalkoxy; (24) -(CH2) _q C0 ₂ R ^A , where q is an integer from zero to four, and R ^A is selected from the group consisting of (a) alkyl, (b) aryl, (c) hydrogen, and (d) arylalkyl; (25) -(CH2) _q CONR ^B R ^c , where q is an integer from zero to four and where R ^B and R ^c are independently selected from the group consisting of (a) hydrogen, (b) alkyl, (c) aryl, and (d) arylalkyl; (26) -(CH2) _q S02R ^D , where q is an integer from zero to four and where R ^D is selected from the group consisting of (a) alkyl, (b) aryl, and (c) arylalkyl ; (27) -(CH2) _q S02NR ^E R ^F , where q is an integer from zero to four and where each of R ^E and R ^F is, independently, selected from the group consisting of (a) hydrogen, (b) alkyl, (c) aryl, and (d) arylalkyl ; (28) thiol; (29) aryloxy; (30) cycloalkoxy; (31 ) arylalkoxy; (31 ) heterocyclylalkyl (e.g., heteroarylalkyl); (32) silyl ; (33) cyano; and (34) -S(0)R ^H where R ^H is selected from the group consisting of (a) hydrogen, (b) alkyl, (c) aryl, and (d) arylalkyl. In some embodiments, each of these groups can be independently unsubstituted or substituted with unsubstituted substituent(s) as described herein for each of the recited groups. For example, the alkylene group of an aryl-Ci- alkylene or a heterocyclyl-Ci -alkylene can be further substituted with an oxo group to afford the respective aryloyl and (heterocyclyl)oyl substituent group.

The term "heterocyclyl alkyl," as used herein, represents an alkyl group substituted with a heterocyclyl group. Each of the heterocyclyl and alkyl portions may be independently unsubstituted or substituted (e.g., optionally substituted heterocyclyl alkyl) as described for the individual groups.

The term "heterocyclylene," as used herein, refers to a divalent group that is heterocyclyl, as defined herein, in which one hydrogen atom is replaced with a valency. Heterocyclylene may be unsubstituted or substituted (e.g., optionally substituted heterocyclylene) as described for heterocyclyl.

The terms "hydroxyl" and "hydroxy," as used interchangeably herein, represent an -OH group.

The term "internucleoside," as used herein, refers to a position within an oligonucleotide that is disposed between two contiguous nucleosides, one nucleoside and an adjacent abasic spacer, or two contiguous abasic spacers.

The term "n-membered ring," as used herein, represents a cycloalkylene, arylene, or heterocyclylene having n atoms in a ring bearing both valencies. The n-membered rings can be unsubstituted or substituted (e.g., optionally substituted n-membered ring) as described herein for cycloalkyl, when n- membered ring is cycloalkylene, for aryl, when n-membered ring is arylene, or for heterocyclyl, when n- membered ring is heterocyclylene.

The term "nitro," as used herein, represents an -NO2 group. The term "nucleobase," as used herein, represents a nitrogen-containing heterocyclic ring found at the 1 ' position of the sugar moiety of a nucleotide or nucleoside. Nucleobases can be unmodified or modified. As used herein, "unmodified" or "natural" nucleobases include the purine bases adenine (A) and guanine (G), and the pyrimidine bases thymine (T), cytosine (C) and uracil (U). Modified nucleobases include other synthetic and natural nucleobases such as 5-methylcytosine (5-me-C or m5c), 5-hydroxymethyl cytosine, xanthine, hypoxanthine, 2-aminoadenine, 6-methyl and other alkyl derivatives of adenine and guanine, 2-propyl and other alkyl derivatives of adenine and guanine, 2-thiouracil, 2-thiothymine and 2- thiocytosine, 5- halouracil and cytosine, 5-propynyl uracil and cytosine, 6-azo uracil, cytosine and thymine, 5-uracil (pseudouracil), 4-thiouracil, 8-halo, 8-amino, 8-thiol, 8- thioalkyl, 8-hydroxyl and other 8- substituted adenines and guanines, 5-halo particularly 5-bromo, 5-trifluoromethyl and other 5-substituted uracils and cytosines, 7-methylguanine and 7-methyladenine, 8-azaguanine and 8-azaadenine, 7- deazaguanine and 7-deazaadenine and 3-deazaguanine and 3- deazaadenine. Further nucleobases include those disclosed in U.S. Pat. No. 3,687,808; those disclosed in The Concise Encyclopedia Of Polymer Science And Engineering, pages 858-859, Kroschwitz, J. I., ed. John Wiley & Sons, 1990; those disclosed by Englisch et al., Angewandte Chemie, International Edition, 1991 , 30, 613; and those disclosed by Sanghvi, Y. S., Chapter 1 5, Antisense Research and Applications, pages 289 302, (Crooke et al., ed., CRC Press, 1993). Nucleobases can be 5-substituted pyrimidines, 6-azapyrimidines and N-2, N-6 and 0-6 substituted purines, including 2-aminopropyladenine, 5-propynyluracil and 5- propynylcytosine. 5-methylcytosine substitutions have been shown to increase nucleic acid duplex stability by 0.6-1 .2° C. (Sanghvi et al., eds., Antisense Research and Applications 1993, CRC Press, Boca Raton, pages 276-278). These may be combined, in particular embodiments, with 2'-0- methoxyethyl sugar modifications. United States patents that teach the preparation of certain of these modified nucleobases as well as other modified nucleobases include, but are not limited to, the above noted U.S. Patent Nos. 3,687,808; 4,845,205; 5,130,302; 5,134,066; 5,175,273; 5,367,066; 5,432,272; 5,457,187; 5,459,255; 5,484,908; 5,502,177; 5,525,71 1 ; 5,552,540; 5,587,469; 5,594,121 ; 5,596,091 ; 5,614,617; and 5,681 ,941 . For the purposes of this disclosure, "modified nucleobases," as used herein, further represents nucleobases, natural or non-natural, which include one or more protecting groups as described herein. The term "nucleoside," as used herein, represents a sugar-nucleobase combination. Nucleoside, as used herein, is a compound, a monovalent group, or a divalent group. The sugar is: ribose, modified ribose (e.g., 2'-deoxyribose), mannose, arabinose, glucopyranose, galactopyranose, 4-thioribose, a morpholino sugar (as found in morpholino oligonucleotides), threose (as found in threose nucleic acids), propanediol (as found in glycol nucleic acids), or a locked nucleic acid (e.g., ribose that is modified to include a bridge (e.g., a -CH2-O- bridge), e.g., connecting 4' and 2' carbon atoms of the ribose). The sugar can be an L- sugar or D-sugar. A modified ribose has a substitution at position 2' with H, OR, R, halo (e.g., F), SH, SR, NH2, NHR, NR2, or CN, where R is an optionally substituted C1-6 alkyl (e.g., (C1-6 alkoxy)-Ci-6-alkyl) or optionally substituted (Ce-14 aryl)-Ci-4-alkyl. In some embodiments, the term "nucleoside" refers to a group having the following structure: , or , in which B ¹ is a nucleobase; R ⁵ is H, halogen (e.g., F), O-protected hydroxyl, or optionally substituted C1-6 alkoxy (e.g., methoxy or methoxyethoxy); Y ¹ is H or C1-6 alkyl (e.g., methyl); R ⁶ is H or a hydroxyl protecting group; and each of 3' and 5' indicate the position of a bond to another group. In some embodiments, the nucleoside is a locked nucleic acid (LNA). Locked nucleosides are known in the art and are described, for example, in US

6,794,499; US 7,084,125; and US 7,053,207. In certain embodiments, the nucleoside is a locked nucleic acid having the following structure:

in which

X is -0-, -S-,— N(R ^N* )— , -C(R ⁸ R ^6* )-, -0-C(R ⁷ R ^7* )-, -C(R ⁶ R ^6* )-0- -S-C(R ⁷ R ^7* )-,

-C(R ⁶ R ^6* )-S- -N(R ^N* )-C(R ⁷ R ^7* )-, -C(R ⁶ R ^6* )-N(R ^N* )-, or -C(R ⁶ R ^6* )-C(R ⁷ R ^7* )-;

B is a nucleobase;

R ^3* is a valency or OR ^A , where R ^A is H or a hydroxyl protecting group;

one or two pairs of non-geminal substituents selected from the group consisting of R ^{1 *} , R ^4* , R ⁵ , R ^5* , R ⁶ , R ^6* , R ⁷ , R ^7* , R ^N* , R ² , R ^2* , and R ³ combine to form one or two biradicals, respectively, where each biradical independently consists of 1 -8 groups independently selected from the group consisting of -C(R ^a R ^b )-, -C(R ^a )=C(R ^a )-, -C(R ^a )=N- -0-, -Si(R ^a ) ₂ - -S-, -SO2-, -N(R ^a )-, and >C=Z, where Z is selected from =0-, =S- =N(R ^a ), and =CH2, and each R ^a and each R ^b is independently hydrogen, optionally substituted C1-12 alkyl, optionally substituted C2-12 alkenyl, optionally substituted C2-12 alkynyl, -OH, Ci-i2-alkoxy, C2-12 alkenyloxy, -COOH, C1-12 alkoxycarbonyl, optionally substituted aryl, optionally substituted aryloyl, optionally substituted aryloxy-carbonyl, optionally substituted aryloxy, optionally substituted heteroaryl, optionally substituted heteroaryloyi, optionally substituted heteroaryloxy-carbonyl, optionally substituted heteroaryloxy, amino, (Ci-6-alkyl)amino, di(Ci-6-alkyl)amino, carbamoyl, (Ci e-alkyl)- amino-carbonyl, di(Ci-6-alkyl)-amino-carbonyl, amino-Ci-6-alkyl-aminocarbonyl, (Ci-6-alkyl)amino-Ci-6- alkyl-aminocarbonyl, di(Ci-6-alkyl)amino-Ci-6-alkyl-aminocarbonyl, -NHCONH2, C2-7-alkanoylamino, C1-6 alkanoyloxy, alkylsulfonyl, C1-6 alkylsulphonyloxy, nitro, azido, -SH, C1-6 thioalkyl, or halo; and

each of the remaining substituents R ^{1 *} , R ² , R ^2* , R ³ , R ^4* , R ⁵ , R ^5* , R ⁶ , R ^6* , R ⁷ , and R ^7* is independently hydrogen, optionally substituted C1-12 alkyl, optionally substituted C2-12 alkenyl, optionally substituted C2-12 alkynyl, hydroxy, C1-12 alkoxy, C2-12 alkenyloxy, -COOH, C1-12 alkoxycarbonyl, C1-12 alkanoyi, formyl, optionally substituted aryl, optionally substituted aryloxy-carbonyl, optionally substituted aryloxy, optionally substituted arylcarbonyl, optionally substituted heteroaryl, optionally substituted heteroaryloxy-carbonyl, optionally substituted heteroaryloxy, optionally substituted heteroarylcarbonyl, amino, (Ci-6-alkyl)amino, di(Ci-6-alkyl)amino, carbamoyl, (Ci-6-alkyl)-amino-carbonyl, di(Ci-6-alkyl)-amino- carbonyl, amino-Ci-6-alkyl-aminocarbonyl, (Ci-6-alkyl)amino-Ci-6-alkyl-aminocarbonyl, di(Ci-6-alkyl)amino- Ci-6-alkyl-aminocarbonyl, C1-6 alkanoylamino, C1-6 alkanoyloxy, C1-6 alkylsulfonyl, C1-6 alkylsulfonyloxy, nitro, azido, -SH, Ci-6-thioalkyl, or halogen; or two remaining geminal substituents may combine to form =0, =S, =NR ^a , =CH2, or a 1 -5 carbon atom(s) alkylene chain which is optionally interrupted one or two heteroatoms independently selected from the group consisting of -0-, -S-, and -(NR ^N )-, where R ^N is hydrogen or Ci-4-alkyl; or two remaining vicinal substituents combine to form an additional bond resulting in a double bond; and R ^N* , when present and not involved in the biradical, is hydrogen or Ci-4-alkyl.

In particular embodiments, the locked nucleic acid has the following structure:

In further embodiments, X is -O- and B is a nucleobase. In some embodiments,

R ^3* is a valency or OR ^A , where R ^A is H or a hydroxyl protecting group;

R ^2* and R ^4* combine to form a biradical consisting of 2-5 groups/atoms selected from -(CR ^* R ^* )r- Y-(CR ^* R ^* )s- -(CR ^* R ^* ),-Y-(CR ^* R ^* )s-Y-, -Y-(CR ^* R ^* ) _r+s -Y-, -Y-(CR ^* R ^* ),-Y-(CR ^* R ^* )s-, -(CR ^* R ^* ) _r+s -, each R ^* is independently hydrogen, halogen, -OH, -SH, amino, optionally substituted Ci-6-alkoxy, optionally substituted C1-6 alkyl, where Y is -0-, -S-, absent, or -N(R ^N )-, and each of r and s is an integer from 0 to 4, provided that the sum r+s is 1 -4, and provided that, when the biradical is -(CR ^* R ^* )r- Y-(CR ^* R ^* )s- then Y is -S- or N(R ^N' )— ; and

each of the substituents R ^{1 *} , R ² , R ³ , R ⁵ , and R ^5* is independently hydrogen, optionally substituted C1-12 alkyl, optionally substituted C2-12 alkenyl, optionally substituted C2-12 alkynyl, -OH, C1-12 alkoxy, C2-12 alkenyloxy, -COOH, C1-12 alkoxycarbonyl, C1-12 alkanoyl, optionally substituted aryl, optionally substituted aryloxy-carbonyl, optionally substituted aryloxy, optionally substituted aryloyi, optionally substituted heteroaryl, optionally substituted heteroaryloxy-carbonyl, optionally substituted heteroaryloxy, optionally substituted heteroaryloyl, amino, (Ci-6-alkyl)amino, di(Ci-6-alkyl)amino, carbamoyl, (Ci-6-alkyl)-amino- carbonyl, di(Ci-6-alkyl)-amino-carbonyl, amino-Ci-6-alkyl-aminocarbonyl, (Ci-6-alkyl)amino-Ci-6-alkyl- aminocarbonyl, di(Ci-6-alkyl)amino-Ci-6-alkyl-aminocarbonyl, -NHCONH2, C2-7-alkanoylamino, C1-6 alkanoyloxy, alkylsulfonyl, C1-6 alkylsulphonyloxy, nitro, azido, -SH, C1-6 thioalkyl, or halo.

The term "nucleotide," as used herein, represents a nucleoside bonded to a phosphate,

phosphorothioate, phosphorodithioate, phosphonate, or phosphoramidate. The term "oligonucleotide," as used herein, represents a compound containing nucleosides and optionally abasic spacers covalently linked to each other through internucleoside bridging groups, e.g., phosphates, phosphorothioates, phoshorodithioates, phosphites, phosphonates, and phosphoramidates. An oligonucleotide includes a total of 2-100 nucleosides and abasic spacers, provided that the

oligonucleotide includes at least one nucleoside. In some embodiments, an oligonucleotide includes 1 -6 (e.g., 1 , 2, or 3) abasic spacers.

The terms "oxa" and "oxy," as used interchangeably herein, represents a divalent oxygen atom that is connected to two groups (e.g., the structure of oxy may be shown as -0-). The term "oxo," as used herein, represents a divalent oxygen atom that is connected to one group (e.g., the structure of oxo may be shown as =0). The term "pseudohalogen," as used herein, represents an optionally substituted alkylsulfonate or optionally substituted arylsulfonate. Non-limiting examples of pseudohalogens include methanesulfonate, trifluoromethanesulfonate, benzenesulfonate, and p-toluenesulfonate.

The term "protecting group," as used herein, represents a group intended to protect a functional group (e.g., a hydroxyl, an amino, or a carbonyl) from participating in one or more undesirable reactions during chemical synthesis (e.g., polynucleotide synthesis). The term "O-protecting group," as used herein, represents a group intended to protect an oxygen containing (e.g., phenol, hydroxyl or carbonyl) group from participating in one or more undesirable reactions during chemical synthesis. The term "N- protecting group," as used herein, represents a group intended to protect a nitrogen containing (e.g., an amino or hydrazine) group from participating in one or more undesirable reactions during chemical synthesis. Commonly used O- and /V-protecting groups are disclosed in Greene, "Protective Groups in Organic Synthesis," 3 ^rd Edition (John Wiley & Sons, New York, 1999), which is incorporated herein by reference. Exemplary O- and /V-protecting groups include alkanoyl, aryloyl, or carbamyl groups such as formyl, acetyl, propionyl, pivaloyl, t-butyl acetyl, 2-chloroacetyl, 2-bromoacetyl, trifluoroacetyl,

trichloroacetyl, phthalyl, o-nitrophenoxyacetyl, a-chlorobutyryl, benzoyl, 4-chlorobenzoyl, 4-bromobenzoyl, f-butyldimethylsilyl, tri-/ ^' so-propylsilyloxymethyl, 4,4'-dimethoxytrityl, isobutyryl, phenoxyacetyl, 4- isopropylpehenoxyacetyl, dimethylformamidino, and 4-nitrobenzoyl. /V-protecting groups useful for protection of amines in nucleobases include phenoxyacetyl and (4-isopropyl)phenoxyacetyl. Exemplary O-protecting groups for protecting carbonyl containing groups include, but are not limited to: acetals, acylals, 1 ,3-dithianes, 1 ,3-dioxanes, 1 ,3-dioxolanes, and 1 ,3-dithiolanes.

Other O-protecting groups include, but are not limited to: substituted alkyl, aryl, and arylalkyl ethers (e.g., trityl; methylthiomethyl; methoxymethyl ; benzyloxymethyl ; siloxymethyl ; 2,2,2,-trichloroethoxymethyl; tetrahydropyranyl ; tetrahydrofuranyl ; ethoxyethyl ; 1 -[2-(trimethylsilyl)ethoxy]ethyl; 2-trimethylsilylethyl ; t- butyl ether; p-chlorophenyl, p-methoxyphenyl, p-nitrophenyl, benzyl, p-methoxybenzyl, and nitrobenzyl) ; silyl ethers (e.g., trimethylsilyl; triethylsilyl ; triisopropylsilyl ; dimethylisopropylsilyl; t-butyldimethylsilyl; t- butyldiphenylsilyl ; tribenzylsilyl; triphenylsilyl; and diphenymethylsilyl) ; carbonates (e.g., methyl, methoxymethyl, 9-fluorenylmethyl ; ethyl ; 2,2,2-trichloroethyl ; 2-(trimethylsilyl)ethyl; vinyl, allyl, nitrophenyl; benzyl; methoxybenzyl; 3,4-dimethoxybenzyl ; and nitrobenzyl).

Other /V-protecting groups include, but are not limited to, chiral auxiliaries such as protected or unprotected D, L or D, L-amino acids such as alanine, leucine, phenylalanine, and the like; sulfonyl- containing groups such as benzenesulfonyl, p-toluenesulfonyl, and the like; carbamate forming groups such as benzyloxycarbonyl, p-chlorobenzyloxycarbonyl, p-methoxybenzyloxycarbonyl, p- nitrobenzyloxycarbonyl, 2-nitrobenzyloxycarbonyl, p-bromobenzyloxycarbonyl, 3,4- dimethoxybenzyloxycarbonyl, 3,5-dimethoxybenzyl oxycarbonyl, 2,4-dimethoxybenzyloxycarbonyl, 4-methoxybenzyloxycarbonyl, 2-nitro-4,5-dimethoxybenzyloxycarbonyl,

3,4,5-trimethoxybenzyloxycarbonyl, 1 -(p-biphenylyl)-l -methylethoxycarbonyl, α,α-dimethyl- 3,5-dimethoxybenzyloxycarbonyl, benzhydryloxy carbonyl, t-butyloxycarbonyl,

diisopropylmethoxycarbonyl, isopropoxycarbonyl, ethoxycarbonyl, methoxycarbonyl, allyloxycarbonyl, 2,2,2-trichloroethoxycarbonyl, phenoxycarbonyl, 4-nitrophenoxy carbonyl, fluorenyl-9-methoxycarbonyl, cyclopentyloxycarbonyl, adamantyloxycarbonyl, cyclohexyloxycarbonyl, phenylthiocarbonyl, and the like, arylalkyl groups such as benzyl, triphenylmethyl, benzyloxymethyl, and the like and silyl groups such as trimethylsilyl, and the like. Useful /V-protecting groups are formyl, acetyl, benzoyl, pivaloyl, t-butylacetyl, alanyl, phenylsulfonyl, benzyl, t-butyloxycarbonyl (Boc), benzyloxycarbonyl (Cbz), phenoxyacetyl, and (4- isopropyl)phenoxyacetyl.

The term "silyl," as used herein, refers to a group of formula -S1R3, where each R is independently alkyl, alkenyl, aryl, or arylalkyl. Silyl can be optionally substituted in the same manner as defined for each R group.

The term "sugar analogue," as used herein, represents a C3-6 monosaccharide or C3-6 alditol (e.g., glycerol), which is modified to replace one hydroxyl group with a bond to an oxygen atom in formula (MIA), (NIB), (MIC), or (MID) (e.g., in formula (IVA), (IVB), (IVC), (IVD), (IVA"), (IVB"), (IVC), (IVD"), (IVA"), (IVB"), (IVC"), or (IVD")). A sugar analogue does not contain a nucleobase capable of engaging in hydrogen bonding with a nucleobase in a complementary strand. A sugar analogue is cyclic or acyclic. Further optional modifications included in a sugar analogue are: a replacement of one, two, or three of the remaining hydroxyl groups or carbon-bonded hydrogen atoms with H; optionally substituted C1-6 alkyl; - (CH2)n-OR ^z , where t1 is an integer from 1 to 6, and R ^z is optionally substituted C1-6 alkyl, optionally substituted C2-6 alkenyl, optionally substituted C2-6 alkynyl, optionally substituted Ce-14 aryl, optionally substituted C3-8 cycloalkyl, optionally substituted (C1-9 heterocyclyl)-Ci-6-alkyl, optionally substituted (Ce-ιο aryl)-Ci-6-alkyl, or optionally substituted (C3-8 cycloalkyl)-Ci-6-alkyl; introduction of one or two

unsaturation(s) (e.g., one or two double bonds); and replacement of one, two, or three hydrogens or hydroxyl groups with substituents as defined for alkyl, alkenyl, cycloalkyl, cycloalkenyl, or heterocyclyl. Non-limiting examples of sugar analogues are optionally substituted C2-6 alkyl, optionally substituted

C2-6 alkenyl, optionally substituted C5 cycloalkyl, optionally substituted C5 cycloalkenyl, optionally substituted heterocyclyl (e.g., optionally substituted pyrrolidinyl, optionally substituted tetrahydrofuranyl, or optionally substituted tetrahydrothiophenyl), optionally substituted (C1-9 heterocyclyl)-Ci-6-alkyl, or optionally substituted (C3-8 cycloalkyl)-Ci -6-alkyl .

The term "stereochemically enriched," as used herein, refers to a local stereochemical preference for one enantiomer of the recited group over the opposite enantiomer of the same group. Thus, a,

oligonucleotide containing a stereochemically enriched phosphorothioate is an oligonucleotide, in which a phosphorothioate of predetermined stereochemistry is present in preference to a phosphorothioate of stereochemistry that is opposite of the predetermined stereochemistry. This preference can be expressed numerically using a diastereomeric ratio (dr) for the phosphorothioate of the predetermined stereochemistry. The diastereomeric ratio for the phosphorothioate of the predetermined stereochemistry is the molar ratio of the diastereomers having the identified phosphorothioate with the predetermined stereochemistry relative to the diastereomers having the identified phosphorothioate with the

stereochemistry that is opposite of the predetermined stereochemistry. The diastereomeric ratio for the phosphorothioate of the predetermined stereochemistry may be75:25 or greater (e.g., 80:20 or greater, 90:1 0 or greater, 95:5 or, or 98:2 or greater).

The term "sulfide," as used herein, represents -S- or =S.

The term "thioalkyl ," as used herein, refers to a divalent group -SR, in which R is alkyl. Thioalkyl may be unsubstituted or substituted (e.g., optionally substituted thioalkyl) as described for alkyl.

The term "thiocarbonyl ," as used herein, represents a C(=S) group. Non-limiting example of functional groups containing a "thiocarbonyl" includes thioesters, thioketones, thioaldehydes, thioanhydrides, thioacyl chlorides, thioamides, thiocarboxylic acids, and thiocarboxylates.

The term "thioheterocyclylene," as used herein, represents a divalent group -S-R'-, where R' is a heterocyclylene as defined herein.

The term "thiol," as used herein, represents an -SH group.

One of skill in the art will recognize that references P-stereogenic groups, compounds containing them , and diastereoselective syntheses utilizing the same are for enantioenriched and diastereoenriched compositions of the compounds (e.g. , enantiomeric ratio of 90:1 0 or greater (e.g ., 95:5 or greater or 98:2 or greater)), where the major stereoisomer is that which is identified either by a structure or by a stereochemical identifier, such as (S) or (R) for the carbon stereocenters and (Sp) or (Rp) for the phosphorus stereocenters.

Detailed Description

The invention provides P-stereogenic groups for diastereoselective synthesis of stereochemical^ enriched P-stereogenic compounds. P-stereogenic groups of the invention can be used in highly diastereoselective synthesis of P-stereogenic phosphorothioates (e.g., with dr of 90:1 0 or greater (e.g. , 95:5 or greater or 98:2 or greater)). Advantageously, P-stereogenic groups (e.g. , those having R ³ and R ⁴ be H)) can be readily accessed through a short (e.g ., a two-step synthesis) from commercially available materials. A P-st r (I D) :

(IA) (IB) (IC) (I D) where

is a single carbon-carbon bond or a double carbon-carbon bond;

each of R ¹ and R ² is independently an optionally substituted C1-6 alkyl or optionally substituted Ce- 10 aryl, or R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring; and

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted Ce-10 aryl.

In some embodiments, the P-stereogenic group is a group of formula (IA) or In certain embodiments, the P-stereogenic group is of the following structure

(MA ) (MB') (IIC) (IID')

(MA") (MB") (IIC") (IID")

In particular embodiments, R ³ and R ⁴ are each H. In some embodiments, the P-stereogenic group is a group of formula (MA), (MB), (MA ), (MB'), (MA"), or (MB").

The P-stereogenic groups of the invention may be provided in a compound of formula (IIIA), (1MB), (IMC), or (MID):

(IIIA) (1MB) (MIC) wherein

is a single carbon-carbon bond or a double carbon-carbon bond;

A is an optionally substituted C1-12 alkyl, optionally substituted C3-10 cycloalkyl, optionally substituted C3-10 cycloalkyl-C-6-alkyl, optionally substituted C1-9 heterocyclyl, optionally substituted C1-9 heterocyclyl-Ci-6-alkyl, sugar analogue, nucleoside, nucleotide, or oligonucleotide;

each of R ¹ and R ² is independently an optionally substituted C1-6 alkyl or optionally substituted C6-10 aryl, or R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring; and

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted C6-10 aryl.

In certain embodiments, the P-ster is of formula (MIC) or (MID'):

(MIC) (MID')

(IVA") (IVB") (IVC) (IVD")

(IVA") (IVB") (IVC") (IVD")

In particular embodiments, A is an optionally substituted C1-12 alkyl, optionally substituted C3-10 cycloalkyl, optionally substituted C3-10 cycloalkyl-C-6-alkyl, optionally substituted C1-9 heterocyclyl, optionally substituted C1-9 heterocyclyl-C-6-alkyl, or sugar analogue. In further embodiments, A is a group of formula (X):

(X)

where

each of R ^A1 , R ^A2 , and R ^A3 is independently H, -OR ^A4 , or— N(R ^A4 )(R ^A5 ); where R ^A4 is optionally substituted -16 alkyl, optionally substituted -16 heteroalkyl, or a protecting group, and R ^A5 is H optionally substituted -16 alkyl, optionally substituted -16 heteroalkyl, or a protecting group; and

each of ml , m2, m3, and m4 is independently an integer from 0 to 1 1 , provided that the quaternary carbon in the structure above is bonded to 0 or 1 atoms other than carbon and hydrogen, and provided that the sum of ml , m2, m3 and m4 is 1 1 or less.

In some embodiments, the compound is of formula (IVA), (IVB), (IVA'), (IVB'), (IVA"), or (IVB"). In other

(IVE) (IVF) (IVE') (IVF') (IVE")

In certain embodiments, P-stereogenic groups may be provided in nucleoside phosphoramidites. The nucleoside phosphoramidites of the invention can be used to prepare oligonucleotides having P- stereogenic phosphorothioates with high diastereoselectivity (e.g., with dr of 90:10 or greater (e.g., 95:5 or greater or 98:2 or greater)). Advantageously, nucleoside phosphoramidites of the invention (e.g., those having R ³ and R ⁴ be H) can be readily accessed through a short synthesis (e.g., a two-step synthesis) from commercially available materials. Accordingly, the nucleoside phosphoramidites of the invention are a practical solution for high-yield synthesis of oligonucleotides having stereochemical^ enriched P-stereogenic phosphorothioates.

The nucleoside phosphoramidites of the invention include a sugar bonded to a nucleobase and to a phosphoramidite of the following structure: where

— is a single carbon-carbon bond or a double carbon-carbon bond;

each of R ¹ and R ² is independently an optionally substituted C1-6 alkyl or optionally substituted Ce- 10 aryl, or R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring; and

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted Ce-10 aryl.

In certain embodiments, the phosphoramidite is of formula (VA) or (VB). In particular embodiments, the phosphoramidite is of formula (VC) '):

(VC) (VD')

In some embodiments, the nucleoside phosphoramidite is of the following structure:

(VIC) (VID) where

B ¹ is a nucleobase; Y ¹ is H or C1-6 alkyl (e.g., methyl);

R ⁵ is H, O-protected hydroxyl, optionally substituted C-6 alkoxy, or halogen (e.g., F); and R ⁶ is a hydroxyl protecting group;

and the remaining variables are as defined for formulas (VA), (VB), (VC), and (VD). In particular embodim ID'):

(VIC) (VID')

In certain embodiments, the phosphoramidite is of the following structure:

(VIIA) (VIIB) (VIIC) (VIID)

(VIIA') (VIIB') (VIIC) (VIID')

(VIIA") (VIIB") (VIIC") (VIID").

In particular embodiments, R ³ and R ⁴ are each H. In some embodiments, the phosphoramidite is of formula (VIIA), (VIIB), (VIIA'), or (VIIB'). In other embodiments, the phosphoramidite is of formula (VIIE), (VIIF), (VIIE'), (VIIF'), (VIIE"), or (VIIF"):

(VI IF")

Diastereoselective Preparation of Oligonucleotides Containing Phosphorothioate Phosphodiester

The nucleoside phosphoramidites of the invention may be used for the diastereoselective preparation of oligonucleotides containing a phosphorothioate phosphodiester using reaction conditions known in the art for the phosphoramidite route for oligonucleotide synthesis.

Typically, a nucleoside phosphoramidite of formula (VA) produces an internucleoside (Rp)- phosphorothioate, and a nucleoside phosphoramidite of formula (VB) produces an internucleoside (Sp)- phosphorothioate.

In a typical oligonucleotide chain growth step, a nucleoside phosphoramidite of the invention is coupled to a nucleoside having a 5'-hydroxyl (e.g. , a nucleoside linked to a solid support) or an oligonucleotide having a 5'-hydroxyl (e.g., an oligonucleotide linked to a solid support) to produce a product

oligonucleotide including an internucleoside phosphite substituted with a ring-opened chiral auxiliary. Typically, the coupling step is performed in the presence of a coupling activator. Coupling activators are known in the art; non-limiting examples of coupling activators are (benzylthio)-l H-tetrazole (BTT), N- phenylimidazolium trifluoromethanesulfonate (PhlMT) , 1 -(cyanomethyl)pyrrolidinium

trifluoromethanesulfonate (CMPT), 1 ,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 4,5-dicyanoimidazole (DCI), 4,5-dichloroimidazole, benzimidazolium trifluoromethanesulfonate (BIT), benzotriazole, 3-nitro- 1 ,2,4-triazole (NT), tetrazole, (ethylthio)-l H-tetrazole (ETT), (4-nitrophenyl)-1 H-tetrazole, 1 - (cyanomethyl)piperidinium trifluoromethanesulfonate, and N-cyanomethyldimethylammonium

trifluoromethanesulfonate. In certain embodiments (e.g., when the nucleoside phosphoramidite includes 2'-deoxyribose), the coupling activator is preferably CMPT. The product oligonucleotide may be an oligonucleotide (e.g. , an oligonucleotide having a total of 2-1 00 nucleosides (e.g., 2 to 50 or 2 to 35) including one or more (e.g. , 1 to 6, 1 to 5, 1 to 4, 1 to 3, 1 to 2, or 1 ) internucleoside groups independently selected from the group consisting of linkers of formula (XIA) and (XIB) :

(XIA) (XIB)

where

is a single carbon-carbon bond or a double carbon-carbon bond;

each of R ¹ and R ² is independently an optionally substituted C1-6 alkyl or optionally substituted

Ce-10 aryl, or R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring ;

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted

R ⁷ is acyl (e.g., alkanoyl).

The oligonucleotides including one or more internucleoside groups of formula (XIA) and/or (XIB) may be intermediates in the synthesis of an oligonucleotide including at least one stereochemical^ enriched internucleoside phosphorothioate. For example, these oligonucleotides may be subjected to a sulfurization reaction with a sulfurizing agent (e.g., Beaucage reagent; 3-((N,N- dimethylaminomethylidene)amino)-3H-1 ,2,4-dithiazole-5-thione (DDTT) ; Ss; or a compound of formula (XA) or (XB)) to produce an oligonucleotide (e.g., an oligonucleotide having a total of 2-1 00 nucleosides (e.g., 2 to 50 or 2 to 35) including one or more (e.g. , 1 to 6, 1 to 5, 1 to 4, 1 to 3, 1 to 2, or 1 ) internucleoside groups independently selected from the group consisting of linkers of formula (XMA) and (XI IB) :

(XMA) (XI IB)

where the variables are as describe for formulae (XIA) and (XIB). Sulfurizing agents are known in the art; non-limiting examples of the sulfurizing agents are Beaucage reagent; 3-((/V,/V-dimethylaminomethylidene)amino)-3H-1 ,2,4-dithiazole-5-thione (DDTT) ; Ss; and compounds of formula (XA) and (XB). The compound of formula (XA) is of the following structure:

R ⁸ -S-S-R ⁸ ,

(XA)

or a salt thereof,

where

each R ⁸ is independently R ⁹ C(X ¹ )-, (R ¹⁰ ) ₂ P(X ¹ )-, or R ^{1 1} S(0) ₂ - where each R ⁹ is independently alkylamino or dialkylamino; each R ¹⁰ is independently alkoxy or aryloxy; each R ^{1 1} is independently hydroxyl, alkyl, aryl, or heteroaryl; and X ¹ is =0 or =S. The compound of formula (XB) is of the following structure:

2 where

X ² is O or S; and

R ¹² is aryl, amino, or alkoxy.

For example, the compound of formula (XB) can be:

The oligonucleotide including one or more internucleoside groups of formula (XIIA) and/or (XIIB) is then fed back into the synthesis, e.g., by deprotecting the 5'-protecting group and treating the resulting 5'- hydroxyl as described above or using a different nucleoside phosphoramidite (e.g., those known in the art). Alternatively, if the synthesis of the oligonucleotide chain is complete, the oligonucleotide may be subjected to further modifications (e.g., capping the 5' end). If the oligonucleotide chain is linked through a linker to solid support, the linker may be cleaved using methods known in the art after the synthesis of the oligonucleotide chain is complete. The remainder of the ring-opened chiral auxiliaries of the invention may be removed from phosphotriesters through hydrolysis with aqueous ammonia (30% (w/w)) (e.g., by heating for 12-24 hours at, e.g., about 55 °C). The remainder of the ring-opened chiral auxiliaries of the invention may be removed before, after, or concomitantly with the oligonucleotide chain removal from the solid support.

A non-limiting example of an oligonucleotide synthesis route is shown in Scheme 1 .

R = O-protecting group

R ⁷ = acyl

As shown in Scheme 1 , compound A, which is a protected nucleoside optionally linked to a solid support, may be subjected to a deprotection reaction to remove the O-protecting group (e.g., DMT) at R ⁶ and produce compound B. Compound B is then coupled to phosphoramidite C to produce phosphite D. In certain embodiments (e.g., when the nucleoside phosphoramidite includes 2'-deoxyribose, e.g., when R ⁵ is H), the coupling activator is preferably CMPT.

Compound D is oxidized using a sulfurizing agent to afford phosphorothioate E with retention of stereochemistry.

Nucleoside phosphoramidites including phosphoramidites of formula (IA), (IB), (IC), and (ID) can be in the synthesis of oligonucleotides in accordance with the procedure described above using reaction conditions known in the art.

Preparation of Nucleoside Phosphoramidites

Phosphoramidite Precursors

The nucleoside phosphoramidites of the invention may be prepared from a compound of formula:

(VINA) (VIIIB) (VIIIC) (VIIID)

where

— is a single carbon-carbon bond or a double carbon-carbon bond;

X is a halogen (e.g., CI or Br) or pseudohalogen;

each of R ¹ and R ² is independently an optionally substituted C1-6 alkyl or optionally substituted Ce 10 aryl, or R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring; and

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted Ce-10 aryl.

In particular embodiments, the precursor to a nucleoside phosphoramidite may be a compound of formula:

(IXA) (IXB) (IXC) (IXD)

(ΙΧΑ') (ΙΧΒ') (IXC) (IXD')

(IXA") (IXB") (IXC") (IXD") where

each of R ³ and R ⁴ is independently H, optionally substituted C1-6 alkyl, or optionally substituted Ce-10 aryl; and

X is halogen (e.g., CI or Br) or pseudohalogen.

A non-limiting example of the preparation of a nucleoside phosphoramidite of the invention is shown in Scheme 2. Scheme 2

H

As shown in Scheme 2, aminoalcohol G can be converted to oxazaphospholane of formula (VIIIA) using an electrophilic source of phosphorus (III), e.g., phosphorus (III) halide (e.g., PC ). An

oxazaphospholane of formula (VIIIA) may be coupled to nucleoside H to give a nucleoside

phosphoramidite of formula (VIA). The reaction conditions useful for this coupling are known in the art and typically involve the use of a sterically hindered organic base (e.g., A/./V-diisopropylethylamine). Typically, the oxazaphospholane formation and phosphoramidite formation are performed in a one-pot transformation without isolation or purification of the oxazaphospholane of formula (VIIIA).

Nucleoside phosphoramidites including phosphoramidites of formula (VA), (VB), (VC), and (VD) can be prepared according to the procedure described above using reaction conditions known in the art.

Aminoalcohol G and its enantiomer can be prepared from the corresponding amino acid using methods and reactions known in the art. Aminoalcohol G can be used in the preparation of compounds containing a P-stereogenic group of formula (IA) or (IB) (e.g., compounds of formula (IIIA) or (NIB)). Aminoalcohol I and its enantiomer for the preparation of phosphoramidites of formula (VC) and (VD) can be prepared from the corresponding amino acids using methods and reactions known in the art. Aminoalcohol I can be used in the preparation of compounds containing a P-stereogenic group of formula (IC) or (ID) (e.g., compounds of formula (IMC) or (MID)). Aminoalcohol I is a compound of the following structure:

where each of R ¹ and R ² is independently optionally substituted C1-6 alkyl or optionally substituted Ce-ιο aryl, or R ¹ and R ² , together with the atoms to which each is attached, combine to form an optionally substituted 5- to 8-membered ring.

Advantageously, when R ³ and R ⁴ are each H, nucleoside phosphoramidites of the invention can be prepared through a short reaction sequence of only three steps, two of which can be carried out in one pot. The following examples are meant to illustrate the invention. They are not meant to limit the invention in any way.

Chiral Auxiliaries and Phosphoramidites

To a solution of (2S)-dihydro-1 H-indole-2-carboxylic acid 1 (1 .63 g, 10.0 mmol) in ether (50 mL) was added a solution of LiAlhU in THF (2M, 7.5 mL, 15.0 mmol) under argon, and the mixture was stirred overnight. After completion of the reaction, the mixture was quenched with Na2SO4-10H2O. The solid was filtered off and washed with ethyl acetate, and the filtrate was dried over anhydrous Na2S04. The mixture was filtered, and the solvent evaporated to give a residue, which was subjected to flash silica gel column purification on an ISCO (hexane/ethyl acetate, 10-70%) to give 1 .44 g (96%) of compound 2 as a gray solid. ¹ H NMR (500 MHz, CDCI _3; ppm): 57.10 (1 H, d, J 7.5 Hz), 7.04 (1 H, t, J 7.5 Hz), 6.75 (1 H, t, J 7.5 Hz), 6.69 (1 H, d, J 7.5 Hz), 4.10-4.06 (2H, m), 3.75 (1 H, dd, J 1 1 .0, 4.0 Hz), 3.60 (1 H, dd, J 1 1 .0, 6.0 Hz), 3.12 (1 H, dd, J 16.0, 9.0 Hz), 2.87 (1 H, dd, J 16.0, 8.0 Hz); ESI MS for C ₉ H NO calculated 149.2, observed [M+H] ⁺ 150.1

To a solution of compound 2 (1 .0 g, 6.7 mmol) in anhydrous THF (5 mL) was added N,N- diisopropylethylamine (2.41 mL, 13.4 mmol) under argon. The resulting mixture was added dropwise to a solution of phosphorus trichloride (0.58 mL, 6.7 mmol) in anhydrous THF (8 mL) at 0 °C under argon. The mixture was warmed to room temp and stirred for 1 .5 h. In a separate round bottom flask, a solution of 5' -(4,4'-dimethoxytrityl)-2'-methoxy-uridine (2.25 g, 4.0 mmol) and A/./V-diisopropylethylamine (4.81 mL, 26.8 mmol) in THF (5 mL) under argon was cooled to -78 °C, and the above mixture was slowly added. The mixture was warmed to room temp, stirred for 3 h, diluted with dichloromethane (30 mL), and washed with saturated aqueous sodium bicarbonate (20 mL). The organic layer dried over anhydrous sodium sulfate and filtered. The filtrate was evaporated to afford a residue, which was subjected to flash silica gel amine column purification on an ISCO (1 -8% methanol in dichloromethane) to give 1 .14 g (39%) of the title compound 3 as a white foam. ESI MS for C40H40N3O9P Calculated 737.7, Observed 738.2 (M+1 ); ³¹ P NMR (202MHz, CDCI3): 6141 .2 (s).

Compound 4 was prepared by the same procedure as reported here for Compound 3 using 5'-0-(4,4'- dimethoxytrityl)-2'-fluoro-uridine as a starting material. Compound 4 was produced in 24% yield. ESI MS for C39H37FN3O8P Calculated 725.7, Observed 748.3 (M+Na); ³¹ P NMR (202MHz, CDCI3) : 5141 .0 (s).

5 6

To a solution of (2S,3aS,7aS)-octahydro-1 H-indole-2-carboxylic acid 5 (1 .69 g, 10.0 mmol) in ether (50 mL) was added a solution of LiAlhU in THF (2M, 7.5 mL, 15 mmol) under argon, and the mixture was stirred overnight. After completion of the reaction, the mixture was quenched with Na2SO4-10H2O, and the solids were filtered off and washed with ethyl acetate. The filtrate was dried over anhydrous Na2S04 and evaporated to give 1 .23 g (79%) of the crude compound 6 as a colorless oil. ¹ H NMR (500 MHz, CDCI3; ppm): 53.70 (1 H, dd, J 1 1 .0, 3.5 Hz), 3.60 (1 H, dd, J 1 1 .0, 6.0 Hz), 3.50-3.40 (1 H, m), 3.24 (1 H, q, J 6.0 Hz), 2.13-2.08 (1 H, m), 1 .94-1 .86 (1 H, m), 1 .75-1 .65 (1 H, m), 1 .65-1 .40 (6H, m), 1 .35-1 .23 (2H, m); ESI MS for C9H11 NO calculated 155.2, observed [M+H] ⁺ 156.1 .

Compound 7 was prepared by the same procedure as reported here for Compound 3 using 5'-0-(4,4'- dimethoxytrityl)-2'-fluoro-uridine as a starting material. ESI MS for C39H43FN3O8P calculated 731 .7, observed 732.2 (M+1 ); ³¹ P NMR (202MHz, CDCI3) : 5140.7 (s).

Compound 8 was prepared by the same procedure as reported here for Compound 3 using 5'-0-(4,4'- dimethoxytrityl)-2'-methoxy-uridine as a starting material. ESI MS for C40H46N3O9P calculated 743.8, observed 742.5 (M-1 ); ³¹ P NMR (202MHz, CDC ): 5140.0 (s).

To a solution of (2/ ^: ?)-dihydro-1 H-indole-2-carboxylic acid 9 (4.90 g, 30.0 mmol) in ether (100 mL) was added a solution of LiAlhU in THF (2M, 22.5 mL, 45 mmol) under argon, and the mixture was stirred overnight. After completion of the reaction, the reaction mixture was quenched with Na2SO4- 10H2O, and the solids were filtered off and washed with ethyl acetate. The filtrate was dried over anhydrous Na2S04, the mixture was filtered, and the solvent evaporated to give a residue, which was subjected to flash silica gel column purification on an ISCO (hexane/ethyl acetate, 10-70%) to give 3.68 g (82%) of compound 10 as a gray solid. ¹ H NMR (500 MHz, CDCI _3; ppm): 57.10 (1 H, d, J 7.5 Hz), 7.04 (1 H, t, J 7.5 Hz), 6.75 (1 H, t, J 7.5 Hz), 6.69 (1 H, d, J 7.5 Hz), 4.1 0-4.06 (1 H, m), 3.75 (1 H, dd, 1 1 .0, 4.0 Hz), 3.60 (1 H, dd, 1 1 .0, 6.0 Hz), 3.12 (1 H, dd, J 16.0, 9.0 Hz), 2.87 (1 H, dd, J 16.0, 8.0 Hz); ESI MS for C9H11 NO calculated 149.2, observed [M+H] ⁺

Compound 11 was prepared by the same procedure as reported here for Compound 3 using 5'-0-(4,4'- dimethoxytrityl)-2'-methoxy-uridine as a starting material. Compound 11 was produced in 56% yield. ESI MS for C40H40N3O9P calculated 737.7, observed 738.2 (M+1 ); ³¹ P NMR (202 MHz, CDCb): 5141 .3 (s).

Compound 12 was prepared by the same procedure as reported here for Compound 3 using 5'-0-(4,4'- dimethoxytrityl)-2'-fluoro-uridine as a starting material. Compound 12 was produced in 72% yield. ESI MS for C39H37FN3O8P Calculated 725.7, Observed 748.3 (M+Na); ³¹ P NMR (202 MHz, CDCI3): 5141 .8 (s).

Compound 13 was prepared by the same procedure as reported here for Compound 3 using 5'-0-(4,4'- dimethoxytrityl)-2'-deoxy-cytidine (/V-acetyl) as a starting material. Compound 13 was produced in 33% yield. ESI MS for C41 H41 N4O8P Calculated 748.8, Observed 747.4 (M-1 ); ³¹ P NMR (202 MHz, CDCI3): 5140.2 (s).

Compound 14 was prepared by the same procedure as reported here for Compound 3 using 5'-0-(4,4'- dimethoxytrityl)-2'-deoxy-cytosine(/V-acetyl) as a starting material. Compound 14 was produced in 27% yield. ESI MS for C41 H41 N4O8P Calculated 748.8, Observed 747.4 (M-1 ); ³¹ P NMR (202 MHz, CDCI3): 5139.7 (s).

Compound 15 was prepared by the same procedure as reported here for Compound 3 using 5'-0-(4,4'- dimethoxytrityl)-2'-methoxy-cytosine (/V-acetyl) as a starting material. Compound 15 was produced in 35% yield. ESI MS for C42H43N4O9P Calculated 778.8, Observed 779.3 (M) ; ³¹ P NMR (202 MHz, CDC ) : 6141 .0(s).

Compound 16 was prepared by the same procedure as reported here for Compound 3 using 5'-0-(4,4'- dimethoxytrityl)-2'-methoxy-adenosine(/V-benzoyl) as a starting material. Compound 16 was produced in 48% yield. ESI MS for C48H ₄ 5N ₆ 08P Calculated 864.8, Observed 865.3 (M) ; ³¹ P NMR (202 MHz, CDCb) : 5140.0 (s).

Compound 17 was prepared by the same procedure as reported here for compound 3 using 5'-0-(4,4'- dimethoxytrityl)-2'-methoxy-guanosine(/V-i-butyryl) as a starting material. Compound 17 was produced in 10% yield. ESI MS for C45H47N6O9P Calculated 846.9, Observed 847.3 (M) ; ³¹ P NMR (202 MHz, CDCb) : 5138.9 (s). Compounds listed in Table 1 were prepared by the same procedure as reported here for compound 3.

Table 1

Synthesis of the Polynucleotide Constructs

All the polynucleotide constructs synthesized were modified at the 2'-ribose sugar position with 2'-F, 2'- OMe, or 2'-deoxy modification. O-protecting groups, such as 2'-OTBDMS, can also be used. Automated polynucleotide synthesis (1 μιηοΙ scale) was carried out with the following reagents/solvents:

Solid support - CPG Glen Uny support

Coupling agent - 0.25 M BTT in acetonitrile

Oxidizer - 0.02 M l ₂ in THF/Pyridine/H ₂ 0 (2x 30 s oxidation per cycle)

Deblock - 3% Trichloroacetic Acid/DCM (2x 40 s deblocks per cycle)

Cap Mix A - THF/ 2, 6-Lutidine/Ac20 (2x 30 s capping per cycle)

Cap Mix B - 1 6% Methyl imidazole in THF (2x 30 s capping per cycle)

Sulfurization - 0.05 M sulfurizing reagent, 3-((/V,/V-dimethylaminomethylidene)amino)-3H-

1 ,2,4-dithiazole-5-thione (DDTT), in 60% pyridine/40% acetonitrile (3x 60 s sulfurization per cycle)

Coupling - Phosphoramidites were suspended to a concentration of 100 mM in anhydrous acetonitrile prior to synthesis, phosphoramidite activation was performed with 2.5-fold molar excess of BTT, 0.25 M in acetonitrile. Activated phosphoramidites were coupled for 3x 60 seconds per cycle

Polynucleotide deprotection and purification protocol:

When polynucleotides contain standard nucleobase protecting groups (such as A-Bz, C-Ac and G-iBu etc.), the following cleavage and deprotection conditions were used: polynucleotides were cleaved and deprotected in 1 .0 mL of AMA (1 :1 ratio of 36% aq.

ammonia and 40% methylamine in methanol) for 2 h at room temperature followed by centrifugal evaporation.

Crude polynucleotide pellets were re-suspended in 100 μΙ_ of 50% acetonitrile/water, briefly heated to 65 °C, and vortexed thoroughly. Total 1 00 μΙ_ crude polynucleotide samples were injected onto reverse phase HPLC with the following buffers/gradient:

Buffer A = 50 mM aqueous triethylammonium acetate (TEAA)

Buffer B = 90% acetonitrile in water

Flow Rate 1 mL/min

Gradient:

0 - 2 min (100% Buffer A / 0% Buffer B)

2 - 42 min (0% to 60% Buffer B)

42 - 55 min (60% to 1 00% Buffer B) Across the dominant reverse phase HPLC peaks, 0.5 mL fractions were collected and analyzed by MALDI-TOF mass spectrometry to confirm the presence of compounds with the desired mass peaks. Purified fractions containing compounds with the correct mass peaks were frozen and lyophilized. Once dry, fractions were re-suspended, combined with corresponding fractions, frozen, and lyophilized to give the final product.

Polynucleotides requiring additional deprotection were initially isolated as described above followed by the necessary secondary deprotection steps (see below): Secondary deprotection of polynucleotides having TBDMS protection:

Reverse phase HPLC-purified polynucleotide products were re-suspended in 219 μΙ_ of anhydrous DMSO, heated briefly to 65 °C, and vortexed thoroughly. To the DMSO solution, 31 μΙ_ of 6.1 M triethylamine trihydrofluoride (TEA.3HF) was added to give a final concentration of 0.75 M. The reaction was allowed to proceed at room temperature for ~1 h per TBDMS-protected hydroxyl modification.

Reaction was monitored by MALDI-TOF mass spectrometry to confirm complete deprotection. Once deprotection was complete, 35 μΙ_ of 3M sodium acetate and 1 mL of butanol were sequentially added. Samples were vortexed thoroughly and placed at -80 °C for 2 h. After 2 h, samples were centrifuged to pellet the polynucleotides. The butanol layer was removed, and the polynucleotide pellet was re- suspended in 1 mL of aqueous 20% acetonitrile. Samples were gel-filtered for isolation of the final polynucleotide construct.

Synthesis of Polynucleotide Constructs with Stereochemically Enriched Internucleoside

Phosphorothioates (PS):

The following modified experimental conditions have been used for the synthesis of polynucleotide constructs including stereochemically enriched internucleoside phosphorothioates from chiral phosphoramidite monomers. Automated polynucleotide synthesis (1 μιηοΙ scale) was carried out with the following reagents/solvents:

Solid support - CPG Glen Uny support

Coupling agent - BTT/ETT/CMPT/phenyl imidazole as required

Oxidizer - 0.02 M l ₂ in THF/Pyridine/H ₂ 0 (2x 30 s oxidation per cycle)

Deblock - 3% dichloroacetic Acid/DCM (2x 40 s deblocks per cycle)

Cap Mix A - THF/2,6-lutidine/Ac20 (2x 30 s capping per cycle)

Cap Mix B - 1 6% methyl imidazole in THF (2x 30 s capping per cycle)

Sulfurization - 0.05 M sulfurizing reagent, 3-((/V,/V-dimethylaminomethylidene)amino)-3H- 1 ,2,4-dithiazole-5-thione (DDTT), in 60% pyridine/40% acetonitrile (3x 120 s sulfurization per cycle)

Coupling - chiral phosphoramidites (e.g., compounds of formula (MA) or (MB)) were suspended to a concentration of 100 mM in anhydrous acetonitrile prior to synthesis, phosphoramidite activation was performed with 2.5-fold molar excess of respective activators as specified (BTT = 0.25 M in acetonitrile, CMPT = 0.5 M in acetonitrile, Ph- Imidazole = 0.5 M in Acetonitrile). Activated chiral phosphoramidites were coupled for 3x 200 seconds per cycle.

Chiral polynucleotide deprotection and purification protocol:

Following automated polynucleotide synthesis, stereopure phosphorothioate containing polynucleotides with standard nucleobase protecting groups (such as A-Bz, C-Ac, and G-iBu etc.) and chiral auxiliary were deprotected and cleaved with the following conditions: DMT protected chiral phosphorothioate polynucleotides on solid support was suspended in 1 .0 mL of aqueous ammonia (30 wt %) and heated at 55 °C for 12-24h, followed by centrifugal evaporation.

- Crude chiral polynucleotide pellets were re-suspended in 1 00 μΙ_ of 50% acetonitrile, briefly heated to 65 °C, and vortexed thoroughly. Total 1 00 μΙ_ crude polynucleotide samples were injected onto reverse phase HPLC with the following buffers/gradient:

• Buffer A = 1 00 mM aqueous triethylammonium acetate (TEAA)

• Buffer B = 90% acetonitrile in water

· Flow Rate = 1 mL/min

• Gradient:

^■ 0 - 2 min (1 00% Buffer A / 0% Buffer B)

^■ 2 - 50 min (0% to 45% Buffer B)

^■ 50 - 55 min (45% to 1 00% Buffer B)

- Across the dominant reverse phase HPLC peaks, 1 .0 mL fractions were collected and

analyzed by MALDI-TOF mass spectrometry to confirm the presence of compounds with the desired mass peaks. Purified fractions containing compounds with the correct mass peaks were frozen and lyophilized. Once dry, fractions were re-suspended, combined with corresponding fractions, frozen, and lyophilized to give the final product.

Analysis of stereochemical purity of phosphorothioate containing polynucleotides:

DMT protected oligonucleotides with stereochemical^ enriched phosphorothioates were analyzed by HPLC/UPLC to determine the diastereoselectivity of Rp and Sp isomers. The absolute stereochemical identity of the internucleoside phosphorothioate identified with an asterisk (*) was determined through comparison of the HPLC traces of the oligonucleotides of the invention to the HPLC traces of authentic racemic and diastereomerically enriched oligonucleotides that were prepared using methods known in the art. The HPLC conditions were as follows:

Reverse Phase H PLC

Column : AdvancedBio Oligonucleotide, 2.1 ^x 1 00 mm , 2.7 μιτι

· Mobile Phase A: 1 00 mM tetraethylammonium acetate in water

Mobile Phase B: acetonitrile

Gradient: 1 0-12% mobile phase B in 45 min

Column Temperature: 60 °C

Flow Rate: 0.35 mL/min

· Detection : 260 nm (UV) For comparison, reference standards of the same oligonucleotide with Rp and Sp isomers were prepared using literature methods as described elsewhere (Oka et al. , Chem. Soc. Rev., 40:5829-5843, 201 1 ; Oka et al., Org. Lett , 1 1 :967-970, 2009; and U.S. pre-grant publication Nos. 2013/01 84450 and

201 5/01 97540).

Diastereomer ratios (SP:RP) have been established by integrating the product peaks in U PLC traces of the prepared oligonucleotides. Absolute stereochemical identity of the dominant diastereomer was determined by comparison to the reference standard. UPLC was performed as follows. Samples were dissolved in water, injected onto UPLC, and analyzed under the following conditions:

· Column : Xbridge C1 8, 4.6 x 1 50 mm , 5 μιτι

• Mobile phase A = 50 mM aqueous triethylammonium acetate (TEAA) in water

• Mobile phase B = Acetonitrile in water

• Flow Rate = 1 mL/min

• Column Temperature = 50 °C

· Detection = 260 nm

• Gradient:

^■ 0 - 1 min (90% mobile phase A/1 0% mobile phase B)

^■ 1 - 30 min (88.5% mobile phase A/1 1 .5% mobile phase B) The stereochemical purity, stereochemical identity, and coupling activators used in the synthesis of the prepared oligonucleotides are shown in Table 2.

Table 2

Oligonucleotide

Entry Activator PN (**) Sp:Rp

(5' -3')

1 uUGAAGUAAA BTT Racemic Racemic Racemic

2 u*UGAAGUAAA BTT (Rp)-OHI (SP) >99.0:<1.0

3 u*UGAAGUAAA BTT (RP)-DHI (SP) >99.0:<1.0

4 u*UGAAGUAAA PhlMT (Rp)-OHI (SP) >99.0:<1.0

5 u*UGAAGUAAA PhlMT (RP)-DHI (SP) >99.0:<1.0

6 u*UGAAGUAAA CMPT (Rp)-OHI (SP) >99.0:<1.0

7 u*UGAAGUAAA CMPT (RP)-DHI (SP) >99.0:<1.0

8 uUGAAGUAAA BTT Racemic Racemic Racemic

9 u*UGAAGUAAA BTT (Rp)-OHI (SP) 91 :11

10 u*UGAAGUAAA BTT (RP)-DHI (SP) >99.0:<1.0

11 u*UGAAGUAAA CMPT (Rp)-OHI (SP) 95.0:5.0

12 u*UGAAGUAAA CMPT (RP)-DHI (SP) >99.0:<1.0

13 u*UGAAGUAAA PhlMT (Rp)-OHI (SP) >99.0:<1.0

14 u*UGAAGUAAA PhlMT (RP)-DHI (SP) >99.0:<1.0

15 u*UGAAGUAAA BTT (Sp)-DHI (ft) 18:82

16 u*UGAAGUAAA BTT (SP)-DHI (Ftp) <1 :>99.0

17 u*UGAAGUAAA CMPT (SP)-DHI (Ftp) 1.7:98.3

18 u*UGAAGUAAA CMPT (SP)-DHI (Ftp) <1 :>99.0

19 u*UGAAGUAAA PhlMT (SP)-DHI (Ftp) 4.2:95.8

20 u*UGAAGUAAA PhlMT (SP)-DHI (Ftp) 7.4:92.6

21 mNUAAGUAAA BTT Racemic Racemic Racemic

22 m*NUAAGUAAA BTT (SP)-DHI (Ftp) 16:84

23 m*NUAAGUAAA BTT (RP)-DHI (SP) 73.9:26.1

24 m*NUAAGUAAA CMPT (SP)-DHI (FIP) <1.0:>99.0

25 m*NUAAGUAAA CMPT (RP)-DHI (SP) 96.3:3.7

26 m*NUAAGUAAA PhlMT (SP)-DHI (FIP) 12.1 :87.9

27 m*NUAAGUAAA PhlMT (RP)-DHI (SP) 74.4:25.6

28 aUGAAGUAAA BTT Racemic Racemic Racemic

29 a*UGAAGUAAA CMPT (SP)-DHI (Ftp) <1.0:>99.0

30 mUGAAGUAAA BTT Racemic Racemic Racemic

31 m*UGAAGUAAA CMPT (SP)-DHI (Ftp) <1.0:>99.0

30 gUGAAGUAAA BTT Racemic Racemic Racemic

31 g*UGAAGUAAA CMPT (SP)-DHI (Ftp) <1.0:>99.0

32 aNUAAGUAAA BTT Racemic Racemic Racemic

33 a*NUAAGUAAA CMPT (RP)-DHI (SP) 98.4:1.6

34 gNUAAGUAAA BTT Racemic Racemic Racemic

35 g*NUAAGUAAA CMPT (RP)-DHI (SP) 90.9:9.1

36 tNUAAGUAAA BTT Racemic Racemic Racemic Oligonucleotide

Entry Activator PN (**) Sp:Rp

(5' - 3')

37 t*NUAAGUAAA CMPT (RP)-DHI (SP) 86.8:13.2

In Table 2, lower case u is uridine having 2'-F and a 3' position bonded to phosphorothioate; lower case bold u is uridine having 2'-OMe and a 3' position bonded to phosphorothioate; lower case a is 2'- deoxyadenosine having a 3' position bonded to phosphorothioate; lower case bold a is adenosine having a 2'-OMe and a 3' position bonded to phosphorothioate; lower case g is 2'-deoxyguanosine having a 3' position bonded to phosphorothioate; lower case bold g is guanosine having 2'-OMe and a 3' position bonded to phosphorothioate; lower case m is 2'-deoxycytidine having a 3' position bonded to phosphorothioate; lower case bold m is cytidine having 2'-OMe and a 3' position bonded to

phosphorothioate; lower case t is 2'-deoxythymidine having a 3' position bonded to phosphorothioate; ^* indicates a stereochemical^ enriched internucleoside phosphorothioate; UPPER CASE LETTERS identify nucleosides having 2'-F and a 3' position bonded to phosphate; UPPER CASE BOLD LETTERS identify nucleosides having 2'-OMe and a 3' position bonded to phosphate; N is a 2'-deoxyguanosine having a 3' position bonded to phosphate; PN means phosphoramidite; ( ^** ) provides stereochemical identity of the internucleoside phosphorothioate identified with ^* in the oligonucleotide column; and DHI and OHI represent the following structures:

(Rp)-DHI (Sp)-DHI (Rp)-OHI

, and , respectively.

Other Embodiments

Various modifications and variations of the described invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention that are obvious to those skilled in the art are intended to be within the scope of the invention.

Other embodiments are in the claims.