“PROCESS FOR THE PREPARATION OF MACROCYCLIC KETONE ANALOGS OF HALICHONDRIN B”

Field of the Invention:

The present invention relates to a novel process for the preparation of macrocyclic ketone analogs of halichondrin B or pharmaceutically acceptable salts thereof and to novel intermediates which are produced during the course of carrying out the novel process.

Background of the Invention:

Halichondrin B is a large naturally occurring polyether macrolide originally isolated from the marine sponge Halichondria okadai with potent antiproliferative activities.

Halichondrin B

A total synthesis of Halichondrin B was published in 1992 (Aicher, T. D. et al. , J. Am. Chem. Soc. 114:3162-3164).

Eribulin, a synthetic macrocyclic ketone analogs of halichondrin B with potent antiproliferative activities is an anticancer drug marketed by Eisai Co, under the trade name Halaven and it is also known as E7389, B1939 and ER-086526.

It was first reported in U.S. Patent No. 6214865. Accordingly, new methods for the synthesis of halichondrin B analogs and particularly, eribulin useful as anti-cancer agents are desirable.

Objects of the Invention:

The object of the present invention is to provide a novel process for preparation of halichondrin B analogs or pharmaceutically acceptable salts thereof.

Yet another object of the present invention is to provide a novel process via new intermediates for the synthesis of halichondrin B analogs or pharmaceutically acceptable salts thereof.

Yet another object of the present invention is to provide a process which is simple, economical and suitable for industrial scale-up.

Statements of Invention:

According to a first aspect of the present invention, there is provided compounds useful in the synthesis of halichondrin B analogs and particularly, eribulin or pharmaceutically acceptable salts thereof.

In one aspect, the invention provides compound of Formula (4A):

4A wherein PG1, is as described herein.

In another aspect, the invention provides compound of Formula (9 A):

9A

wherein PG1, and PG2 are as described herein.

In another aspect, the invention provides compound of Formula (14A):

14A

wherein PG2, and PG3 are as described herein.

In yet another aspect, the invention provides compound of Formula (6B)

wherein PG3, PG4 and X4 are as described herein.

In yet another aspect, the invention provides compound of Formula (9B)

9B

wherein PG3, PG4 and Xe are as described herein.

In yet another aspect, the invention provides an improved batch process for the synthesis of compound of Formula (5C):

5C

wherein PGs, PG9, PGio,PGn, PGi2, R, Ri, R2 and X ₇ are as described herein.

In yet another aspect, the invention provides a process to prepare halichondrin analogs and particularly, eribulin or pharmaceutically acceptable salts thereof, from the compound of Formula 4A, 9A, 14A, 6B, 9B and 5C.

The halichondrin analogs and particularly, eribulin or pharmaceutically acceptable salts thereof, so prepared may be formulated with one or more pharmaceutically acceptable excipients to provide a pharmaceutical composition. Such excipients and compositions are well known to those skilled in the art.

The details of one or more embodiments of the invention are set forth in the description below. Other features, objects, and advantages of the invention will be apparent from the description and from the claims. DETAILED DESCRIPTION OF THE INVENTION:

The present invention provides a process for the preparation of halichondrin B analogs and particularly, eribulin or pharmaceutically acceptable salts thereof, which process is economical, fast and which results in a high purity halichondrin B analogs.

At various places in the present specification, substituents of compounds of the invention are disclosed in groups or in ranges. It is specifically intended that the invention include each and every individual sub combination of the members of such groups and ranges.

For example, the term "Cl-6 alkyl" is specifically intended to individually disclose methyl, ethyl, C3 alkyl, C4 alkyl, C5 alkyl, and C6 alkyl.

The term“ leaving group“ include halide (X) such as chloro, bromo, fluoro, iodo and a sulfonate such as mesylate, besylate, easylate, tosylate, triflate, nonaflate or fluorosulfonate.

The term PG“ hydroxyl protecting groups” include, but are not limited to the protecting groups for hydroxy delineated in Wuts and Greene, Protective Groups in Organic Synthesis, 4th ed., John Wiley & Sons: New Jersey, (2007), which is incorporated herein by reference in its entirety.

In some embodiments, PG is benzyloxycarbonyl (Cbz), 2,2,2- trichloroethoxycarbonyl (Troc ), 2-(trimethylsilyl)ethoxycarbonyl (Teoc), 2-( 4- 20 trifluoromethylphenylsulfonyl)ethoxycarbonyl (Tsc ), t-butoxycarbonyl (BOC), 1- adamantyloxycarbonyl (Adoc ), 2-adamantylcarbonyl (2-Adoc ), 2,4-dimethylpent- 3- yloxycarbonyl (Doc), cyclohexyloxycarbonyl (Hoc), 1,1 -dimethyl-2, 2,2- trichloro ethoxycarbonyl (TcBOC), vinyl, 2-chloroethyl, 2-phenylsulfonylethyl, allyl, benzyl, 2-nitrobenzyl, 4-nitrobenzyl, diphenyl-4-pyridylmethyl, N',N'- dimethylhydrazinyl, methoxymethyl, t-butoxymethyl (Bum), benzyloxymethyl (BOM), or 2-tetrahydropyranyl (THP). In some embodiments, PG is tri(Cl-4 alkyl)silyl (e.g., tri(isopropyl)silyl). In some embodiments, PG is 1, 1- diethoxymethyl. In some embodiments, PG is 2-(trimethylsilyl)ethoxymethyl (SEM). In some embodiments, PG is N-pivaloyloxymethyl (POM). In some embodiments, PG forms an ester, such as acetyl, benzoyl or pivaloyl. In some embodiments, PG forms an ether such as b- methoxyethoxymethyl ether (MEM), trityl (Tr), dimethoxy trityl( DMT),methoxymethyl ether ( MOM), P- toluenesulphonyl ( Ts), tert-butylsilyl (TBS). In some embodiments, PG forms silyl protection such as tert-butyldimethylsilyl (TBDMS), tri-isoprolylsilyloxy methyl (TOM), tri-isopropylsilyl (TIPS), p-Methoxybenzyl (PMB), Methoxybenzyl (MPM).

In one aspect, the present invention provides processes for preparing intermediate compounds useful for producing halichondrin B analogs and particularly, eribulin or pharmaceutically acceptable salts thereof.

In another aspect, the present invention provides intermediate compounds of any of the intermediates described herein.

As described above, the present invention provides intermediate compound of Formula (4 A)

4A

wherein PG1, is as described herein.

In certain embodiments PGi of Formula (4A), taken with the oxygen atom(s) to which it is bound, is silyl ethers or arylalkyl ethers. For example, PGi, is t- butyldimethyl silyl (TBS), t-butyldiphenylmethyl silyl (TBDPS), benzyl (Bz), pivaloyl (Pv), trityl (Tr) or tosyl (Ts). In another embodiment, PGi, taken with the oxygen atom(s) to which it is bound, is arylalkoxy ether for examples p- methoxybenzyl (PMB) ether.

In an embodiment, compound of Formula (4A), is prepared by a process which comprises steps of,

(i) reacting compound of Formula (1A)

with a protecting agent ( PGi-X) in the presence of a base to obtain compound of Formula (2A);

2A

(ii) reacting the compound of Formula (2A) with a suitable reducing agent to obtain aldehyde of Formula (3 A);

and,

(iii) reacting the aldehyde of Formula (3 A) with

(methoxymethyl)triphenylphosphonium halide

OMe

Ph ₃ P ¹ x ^L 1

to obtain compound of Formula (4A);

wherein PGi is as defined above, X is a leaving group selected from halide and Xi a leaving group, preferably chloride or bromide , more preferably chloride. As described above, the present invention provides intermediate compound of Formula (9 A)

wherein each of PGi, and PG2 are independently hydrogen or a hydroxyl protecting group.

In certain embodiments PGi, and PG2 of Formula (9 A), are same or different protecting groups selected from silyl ethers, arylalkyl ether and arylalkoxy ether. For example, in other embodiments, one or two of PGi, and PG2 taken with the oxygen atom(s) to which they are bound, are t-butyldimethylsilyl (TBS), t- butyldiphenylmethylsilyl (TBDPS), benzyl (Bz), pivaloyl (Pv), trityl (Tr), tosyl (Ts) or p-methoxybenzyl (PMB). For example, one or both of PGi and PG2 are TBS or PMB, or both PGi and PG2 are TBS.

In an embodiment, compound of Formula (9A), is prepared by a process which comprises steps of,

a) reduction of compound of Formula (4A)

4A

with a suitable protonating agent to obtain compound of Formula (5 A)

5A b) intermolecular coupling (Alois Furstner coupling) of compound of Formula (5 A) with compound of Formula (6 A)

6A

to obtain compound of Formula (7 A)

c) Protecting the compound of formula 7 A using suitable protecting agent to form compound of Formula (8A):

and,

d) reacting the compound of formula 8A with ozone, to form aldehyde of Formula ( 9 A) wherein each of PGiand PG2 are as defined above;

and,

X2 is a leaving group, preferably halide, more preferably selected from bromo, chloro and iodo.

As described above, the present invention provides intermediate compound of Formula (14A)

14A

wherein each of PG2, and PG3 are independently hydrogen or a hydroxyl protecting group.

In certain embodiments PG2, and PG3 of Formula (14A), are same or different protecting groups selected from silyl ethers, arylalkyl ether and arylalkoxy ether. For example, in other embodiments, one or two of PG2, and PG3 taken with the oxygen atom(s) to which they are bound, are t-butyldimethylsilyl (TBS), t- butyldiphenylmethylsilyl (TBDPS), benzyl (Bz), pivaloyl (Pv), trityl (Tr), tosyl (Ts) or p-methoxybenzyl (PMB). For example, one or both of PG2, and PG ₃ are TBS or TBDPS, or both PG2, and PG3 are TBS.

In an embodiment, compound of Formula (14A), is prepared by a process which comprises steps of;

a) intermolecular coupling ( Nozaki-Hiyama-Kishi [NHK] coupling) of compound of Formula (9 A)

with compound of Formula

to form compound of Formula (11A):

b) intramolecular cyclization of compound of 11A using Ag ₂ 0/ AgOTf to form compound of Formula (12A):

c) selective deprotection of compound of formula 12 A using suitable deprotecting agent to form compound of Formula (13 A)

and;

d) oxidation with suitable oxidizing agent to form compound of Formula (14A). wherein PGi, PG2 and PG3 are as defined above; and X3 and X4 are leaving group.

In some embodiments, X3 is a halide, such as iodide. In other embodiments, X3 is (Cl- C6) alkyl sulfonate, (C6-C10 aryl or C1-C6 heteroaryl) sulfonate, (C6- C15)aryl(Cl- C6)alkyl sulfonate, or (Cl -C6) heteroaryl(Cl -C6) alkylsulfonate. Specific leaving groups include mesylate, toluenesulfonate, isopropylsulfonate, phenyl sulfonate, or benzyl sulfonate.

In some embodiments, X ₄ is preferably halide, more preferably selected from bromo, chloro and iodo.

In some embodiments, the process further comprises preparing the compound of Formula (16A);

comprising steps of

a) reacting compound of Formula (14A) with methyl magnesium halide (MeMgXs) to form compound of Formula (15A) ;

and,

b) converting compound of Formula (15 A) to form the compound of Formula (16A); wherein PG2 and PG3 are as defined above; PGs PGr _> and PG ₇ are independently hydrogen or a hydroxyl protecting group and X5 is more preferably selected from bromo, chloro and iodo. In certain embodiments PGs PGr, and PG7, are same or different protecting groups selected from silyl ethers, arylalkyl ether and arylalkoxy ether. For example, in other embodiments, one or two of PGs, PG6 and PG7 taken with the oxygen atom(s) to which they are bound, are t-butyldimethylsilyl (TBS), t- butyldiphenylmethylsilyl (TBDPS), benzyl (Bz), pivaloyl (Pv), trityl (Tr), tosyl (Ts) or p-methoxybenzyl (PMB). For example, one or all of PGs. PGr, and PGr are Pv, Ms or Tf, or all PGs, PG ₆ and PG7 are Pv.

Compound (16A) is one of the key intermediate in the synthesis of Eribulin.

Accordingly, an embodiment of the process for the preparation of compound of Formula (14A) and its conversion to compound of Formula (16A) is as shown in Scheme A.

Scheme A

The compounds of Formula 4A, 7A, 8A, 9A, 11A, 12A, 13A, and 14A are hitherto unreported intermediates useful in the process for the preparation of halichondrin B analogs as described herein.

In an embodiment, the hydroxyl group on (S)-m ethyl 3-hydroxy-2- methylpropanoate of Formula (1A) is protected using suitable protecting group to obtain compound of Formula (2A).

Preparation of compounds can involve the protection and deprotection of various chemical groups. The need for protection and deprotection, and the selection of appropriate protecting groups can be readily determined by one skilled in the art. The chemistry of protecting groups can be found, for example, in Greene, et al., Protective Groups in Organic Synthesis, 4d. Ed., Wiley & Sons, 2007, which is incorporated herein by reference in its entirety. Adjustments to the protecting groups and formation and cleavage methods described herein may be adjusted as necessary in light of the various substituents. The protective groups are independently selected from esters, carbonates, carbamates, sulfonates, and ethers.

Preferably, the alcohol is protected as either benzyl (Bn), allyl, p-methoxybenzyl (PMB) or diphenylmethyl (DPM) ether. Trichloroacetimidate is used to form the ether in the presence of a Bronsted or Lewis acid. Preferably, hydroxy protection reaction is performed under anhydrous conditions in the presence of an inert solvent using p-methoxybenzyl-2,2,2-trichloroacetimidate, or diphenylmethyl trichloroacetimidate.

Preferably, the reaction is carried out at a temperature in the range of from about - lO°C to about 40°C for about 1 hour to about 24 hours. More preferably the reaction step is carried out at a temperature in the range from about 0 to about 30°C, for about 5 hours to about 20 hours.

Alternatively 2-(4-Methoxybenzyloxy)-4-methylquinolin may be reacted with methyl triflate in the presence of alcohols to generate a neutral organic salt that transfers the pr/ra-methoxybenzyl (PMB) protecting group onto alcohols in high yield and under mild conditions.

In an embodiment, ester group of compound (2A) is reduced with DIBAL-H or an excess of lithium aluminum hydride to aldehyde of Formula ( 3A).

The reduction step is performed in the presence of polar aprotic solvent such as THF under inert atmosphere at a temperature in the range of from about -70°C to about -60°C for about 30 minutes to about 5 hours.

In an embodiment, aldehyde (3A) is reacted with (methoxymethyl) triphenylphosphonium halide and a base to form alkene of Formula (4A). The Wittig reaction is performed under salt free, aprotic condition in the presence of polar aprotic solvent such as THF under inert atmosphere at a temperature in the range of from about -lO°C to about 30°C for about 30 minutes to about 5 hours. The product obtained is optionally purified on column chromatography.

In an embodiment, alkene of Formula (4 A), is further protonated in aqueous acid to obtain aldehyde of Formula (5A). Preferably the reaction is performed in the presence of carboxylic acid aqueous acetic acid, more preferably acetic acid. The acid catalyzed hydration is performed at a temperature in the range of from about lO°C to about 60°C for about 30 minutes to about 20 hours.

In an embodiment, aldehyde of Formula (5 A) is subjected to an intermolecular Alois Furstner coupling reaction with halide of Formula (6A). The asymmetric coupling reaction is, preferably carried in the presence of CrC12 and a ligand in the presence of a catalytic amount of vitamin B 12 or cobalt phthalocyanine. The ligand used is preferably selected from sulfonamide ligands such as sulfonamide-A, sulfonamide-B and sulfonamide-C.

Sulfonamide-A Sulfonamide-B Sulfonamide-C

Cr-Co bimetallic catalyst-promotes redox addition of vinyl halides to aldehydes. Addition of (Bn)(n-Bu)3NCl or Et3NTTCl, and LiCl enhances the coupling efficiency. A key advantage is the high chemoselectivity toward aldehydes. The liberated chromium (III) salt is reduced to chromium(II) with manganese powder or via electrochemical reduction and can take part in the reaction again. Alternatively palladium acetate may be added as co-catalyst to enhance the rate of the reaction. The coupling is conducted in the presence of a polar aprotic solvent such as THF, DMSO, and acetonitrile at a temperature in the range of from about 10°C to about 40°C for about 1 hour to about 25 hours.

The selective activation of the alkyl iodide and subsequent Cr/Co-catalysed coupling with the aldehyde provided the desired product with a high level of diastereoselectivity.

In an embodiment, hydroxy group of compound (7 A) is protected using suitable protecting agent. Preferably, the protection reaction is performed under anhydrous conditions in the presence of a polar protic solvent such as THF, MTBE, DMF, as PMB, TBS,TBDMS, Pv, Bn ether.

In an embodiment, alkene of compound (8A), is cleaved using ozone in a suitable inert solvent such as MDC. Preferably, ozone is purged at the temperatures at which these reactions are done (usually dry-ice/acetone, or -78°C) where ozonides are fairly stable. To obtain the final products (as well as to get rid of any excess ozone), the reductive workup is performed. In reductive workup, a reagent either zinc (Zn), dimethyl sulfide (Me2S) or triphenylphosphine (Ph3P), is added that will cleave the 0-0 bond. Warming of the solution then results in the desired aldehyde (9 A).

In an embodiment, an intermolecular coupling reaction of aldehyde of Formula (9A ) and halide of Formula (10A), is a chromium-induced redox reaction. The coupling reaction is, Cr-Ni bimetallic catalyst-promotes redox addition of vinyl halides to aldehydes. A key advantage is the high chemoselectivity toward aldehydes. Alternatively, catalytic amount of chromium(II) which is regenerated by reduction with manganese or via electrochemical reduction, or palladium acetate may be added as co-catalyst to enhance the rate of the reaction. In a preferred embodiment the catalyst used for the coupling reaction is NiCk/CrCh. The coupling is preferably carried in the presence of a ligand and polar aprotic solvent such as THF, DMSO, and acetonitrile at room temperature for about 5 to 20 hours. The ligand used is preferably selected from sulfonamide ligands such as sulfonamide-A, sulfonamide-B and sulfonamide-C.

In an embodiment compound (11A) undergoes intramolecular cyclization using silver (I) oxide and silver trifluoromethanesulfonate to form compound of Formula (12A). The cyclization is conducted in the presence of a polar aprotic solvent such as THF, DMSO, and acetonitrile at a temperature in the range of from about 0°C to about 30°C for about 1 hour to about 30 hours.

Selective deprotection of (12A) using suitable deprotecting agent forms compound of Formula (13A). The -methoxybenzyl (PMB) ethers and their somewhat less acid sensitive congeners, the 2-naphthylmethyl (Nap) ethers, are staple protecting groups in organic synthesis in general, and especially in oligosaccharide synthesis, owing to their facile oxidative cleavage with either dichlorodicyanoquinone (DDQ) or ceric ammonium nitrate (CAN). Optionally an additive such as 2-amino-2- methyl-1 -propanol (AMP), may be added to trap formaldehyde thereby suppressing the formation of hydroxymethyl derivative. The ethers are preferably cleaved in the presence of aqueous solvents such as acetonitrile. The deprotection is conducted at a temperature in the range of from about lO°C to about 30°C for about 1 hour to about 10 hours.

In an embodiment compound (13A) is oxidized with suitable oxidizing agent to form the aldehyde intermediate of Formula (14A). In one embodiment, for example and without limitation, the oxidation is performed using a chromium-based reagent, such as Collins reagent, pyridinium dichromate (PDC) or pyridinium chlorochromate (PCC); dimethyl sulfoxide (DMSO), such as, Swem oxidation, Moffatt oxidation or Doering oxidation; or hypervalent iodine compounds, such as, Dess-Martin periodinane or 2-iodoxybenzoic acid. Preferably oxidation is performed using Dess-Martin periodinane reagent in the presence of non polar solvent such as DCM. The reaction mixture is stirred at 20°C to about 30°C for about 30 minutes to about 5 hours.

In an embodiment compound of Formula (14A) is reacted with Grignard reagent such as with methyl magnesium halide to form compound of Formula (15A). The reaction is performed under anhydrous condition using suitable inert solvent such as THF at a temperature of -30°C to about -lO°C for about 10 minutes to about 2 hours.

Intermediate compound (15A) is then converted to compound (16A) by following the methodology as described in the WO 2005/118565.

In one preferred embodiment, when X is trichloroacetimidate, Xi is chloro, X2 is iodo, X3 is iodo, X4 is chloro and X5 is bromo. PGi is 4-Methoxybenzyl (PMB), PG2 is t-butyldimethyl silyl (TBS), PG3 is tert-butyldimethylsilyl(TBDMS), PG5 is pivaloyl (Pv) , PG6 is Mesyl (Ms) and PG7 is triflate (Tf); the compound (14A) obtained by the process of the invention includes compound of formula (14A1):

Accordingly, a process for preparing a compound of formula (14A1) and its conversion to (16A1) according to the present invention is exemplified in Scheme Al .

Scheme A1

The compounds of Formula 4A1, 7A1, 8A1, 9Al,l lAl, 12A1, 13A1, and 14A1 are hitherto unreported intermediates useful in the process for the preparation of halichondrin B analogs as described herein.

Intermediate 16A1 obtained by the process of the present invention is converted to Eribulin by using methodology known in the prior art such as WO 2005/118565.

In yet another aspect, the invention provides compound of Formula (6B).

In certain embodiments PG3 and PG4 of Formula (6B), are same or different protecting groups selected from silyl ethers, arylalkyl ether and arylalkoxy ether. For example, in other embodiments, one or two of PG3 and PG4 taken with the oxygen atom(s) to which they are bound, are t-butyldimethylsilyl (TBS), t- butyldiphenylmethylsilyl (TBDPS), benzyl (Bz), pivaloyl (Pv), trityl (Tr), tosyl (Ts) or p-methoxybenzyl (PMB). For example, one or both of PG3 and PG4 are TBS, TBDMS or PMB, or both PGi and PG2 are TBS; X4 is a leaving group.

In some embodiments, X4 is preferably halide, more preferably selected from bromo, chloro and iodo.

In an embodiment, compound of Formula (6B), is prepared by a process which comprises steps of;

(i) dihydroxylation of alkene compound of Formula (1B)

1 B

with a suitable hydroxylating agent, to form vicinal diol of Formula ( 2B)

(ϋ) oxidative cleavage of diol using periodate to form aldehyde of Formula ( 3B)

and;

(iii) intermolecular coupling ( Nozaki-Hiyama-Kishi [NΉK] coupling) of compound of Formula (3B) with compound of Formula (5B)

to obtain compound (6B), wherein PG3 and PG4 are as defined above; and X3 and X ₄ are leaving group, preferably halide, more preferably selected from bromo, chloro and iodo.

In some embodiments, the process further comprises preparing the compound of Formula (5B); by haloboration of alkyne compound of Formula (4B)

with B- Bromo- or B-iodo-9-borabicyclo[3.3. l]-nonane (B-X-9-BBN) and other haloboranes to give corresponding l-halo-l-alkenes of Formula (5B).

In yet another aspect, the invention provides compound of Formula (9B)

wherein PG3, and PG4 are as described above and X| is halide preferably iodo. In an embodiment, compound of Formula (9B), is prepared by a process which comprises steps of;

a) intramolecular cyclization of compound of Formula (6B), using Ag ₂ 0/ AgOTf to form compound of Formula (7B);

b) reacting compound of Formula (7B) with methyl magnesium halide (MeMgXs) to form compound of Formula (8B);

c) reacting the compound of formula 8B with hydrazine hydrate to obtain intermediate hydrozone followed by subsequent iodination to obtain vinyl iodide of Formula (9B), wherein PG3, PG4 and Xe are as defined above and X5 is a leaving group, preferably halide, selected from bromo, chloro and iodo; more preferably bromo.

In some embodiments, the process further comprises preparing the compound of Formula (12B);

comprising steps of :

a) deprotecting vinyl iodide of Formula (9B) using suitable deprotecting agents such as PTSA or HC1 results in the diol compound of Formula (10B).

b) selectively protecting terminal hydroxy group of compound of formula 10B with suitable protecting group to obtain compound (1 IB);

and;

c) selectively protecting the compound of formula 11B with suitable protecting group to obtain compound (12B);

wherein PG3, PG4, PGs, PG6 and Xe are as defined above.

Compound (9B) is one of the key intermediate in the synthesis of Eribulin.

Accordingly, an embodiment of the process for the preparation of compound of Formula (9B) and its conversion into compound of Formula (12B) is as shown in Scheme B.

Scheme B

The compounds of Formula 6B and 9B are hitherto unreported intermediates useful in the process for the preparation of halichondrin B analogs as described herein. The bracket indicates, that the intermediate could be isolated, but not isolated in the process of the present invention.

Hydroxylation of compound of Formula (1B) is carried out using dilute potassium permanganate (KMn04) or osmium catalyst. A preferred osmium catalyst is osmium tetroxide (0s04). Optionally, a stoichiometric amount of an oxidant [e.g. K3Fe(CN) ₆ or /V-methyl morpholine oxide (NMO)] and a buffered solution may be added to ensure a stable pH, since the reaction proceeds more rapidly under slightly basic conditions. Alternatively, hydroxylation may be carried out by the Woodward Reaction to give corresponding diol of Formula (2B).

Preferably, the hydroxylation is performed in the presence of aqueous solvents at a temperature in the range of from about -lO°C to about 30°C for about 1 hour to about 24 hours.

Oxidative cleavage of diol using periodate such as sodium periodate or potassium periodate, preferably sodium periodate (NaIQ4) breaks apart 1,2-diols (vicinal diols) to form aldehyde of Formula (3B).

The Lemieux-Johnson oxidation proceeds in a two step manner, beginning with dihydroxylation of the alkene (IB) by osmium tetroxide, followed by a Malaprade reaction to cleave the diol (2B) using periodate. Excess periodate is used to regenerate the osmium tetroxide, allowing it to be used in catalytic amounts.

In one embodiment, intermediate (1B) is converted to (3B) without isolation of intermediate (2B).

Optionally, a non-nucleophilic base, such as 2,6-lutidine, can be added to improve on the yield. 0s0 ₄ may be replaced with a number of other Osmium compounds. Periodate may also be replaced with other oxidising agents, such as oxone. In an embodiment, aldehyde of Formula (3B) is subjected to an intermolecular NHK coupling reaction with halide of Formula (5B) to obtain compound (6B).

The asymmetric coupling reaction is, preferably carried in the presence of CrCh and a ligand in the presence of a catalytic amount of MC12 . The ligand used is preferably selected from sulfonamide ligands such as sulfonamide- A, sulfonamide- B and sulfonamide-C.

The coupling is conducted in the presence of a polar aprotic solvent such as TF1F, DMSO, and acetonitrile at a temperature in the range of from about 0°C to about 40°C for about 1 hour to about 25 hours.

The selective activation of the alkyl iodide and subsequent Cr/Co-catalysed NHK coupling with the aldehyde provided the desired product with a high level of diastereoselectivity.

In an embodiment compound (6B) undergoes intramolecular cyclization using silver(I) oxide and silver trifluoromethanesulfonate to form compound of Formula (7B). The cyclization is conducted in the presence of a polar aprotic solvent such as THF, DMSO, and acetonitrile at a temperature in the range of from about 0°C to about 30°C for about 1 hour to about 30 hours.

In one embodiment, intermediate (5B) is converted to (7B) without isolation of intermediate (6B).

In an embodiment compound (5B) is prepared by haloboration of alkyne compound of Formula (4B). Haloboration reaction is carried out using B-iodo BBN at -10°C to room temperature for about 30 minutes to about 2 hours. Preferably reaction is conducted under inert condition using inert solvent such as DCM. In an embodiment Weinreb amide of Formula (7B) is treated with an organometallic reagent such as a Grignard reagent or organolithium reagent to form acyl compound of Formula (8B). Most commonly employed Grignard reagents are methyl magnesium halide (MeMgXs) , preferably methyl magnesium bromide. Most commonly employed lithiates are methyllithium, ethyllithium, tert- butyllithium, n-butyllithium, isopropyllithium, and cyclohexanyllithium, preferably methyllithium. The reaction is performed under anhydrous condition using suitable inert solvent such as THF or diethylether at a temperature of -30°C to about -lO°C for about 10 minutes to about 2 hours.

In an embodiment acyl compound (8B) is reacted with hydrazine hydrate to obtain intermediate hydrazone followed by subsequent iodination to obtain vinyl iodide of Formula (9B). Hydrazone iodination is an organic reaction in which a hydrazone is converted into a vinyl iodide by Shapiro reaction of molecular iodine and a non- nucleophilic base such as TEA, DBU and 2-tert-butyl-l, 1,3,3- tetramethylguanidine in inert solvent such as ethanol, toluene, diethylether

Preferably, compound (8B) is reacted with hydrazine and triethylamine in ethanol at reflux to the hydrazone followed by reaction of the hydrazone with iodine in the presence of TEA in diethylether at room temperature.

The hydroxyl protecting groups of compound Formula (9B) are removed by appropriate means to afford compound of Formula (10B). One of the ordinary skilled in the art would recognize that the methods appropriate to achieve removal of the protecting groups of compound of Formula (9B) depend upon the actual protecting groups used and include those described in the“Greene”. In one embodiment, for example and without limitation, when each of the protecting groups of compound of Formula (9B) is a TBS group, then removal may be achieved by treating with tetra-butyl ammonium fluoride (TBAF). In another embodiment, for example and without limitation when each of the protecting groups of compound of Formula (9B) is either a TBS group or a TBDPS group then removal may be achieved by treating with HC1 solution.

Preferably, deprotection is achieved by using hydrogen chloride in anhydrous solvent such as IP A, methanol or dioxane for about 30 min to about 5 hours at room temperature.

The details of which are set forth in the examples infra.

The deprotection of protected diol using suitable deprotecting agents results in the diol compound of Formula (10B).

Diol compound of Formula (10B) is useful intermediate for preparing various Halichondrin B analogs and particularly, eribulin or pharmaceutically acceptable salts thereof.

A selective protection of primary alcohol of compound of Formula (10B) is carried out by converting the alcohol into a protecting group to form an intermediate compound (11B) followed by converting the second alcohol into a leaving group to form an intermediate compound (12B).

In an embodiment, selective protection is carried out by using PvCl, TBSPSC1, TBSC1,TS20, TsCl, TMSOTf or MsCl in presence of a base such as collidine, lutidine or TEA in the presence of suitable solvent.

In one preferred embodiment, when X3 is iodo, X ₄ is chloro, X5 is bromo and X 6 is iodo. PG3 is tert-butyldimethylsilyl (TBDMS), PG4 is tert-butylsilyl (TBS), PG5 is pivaloyl (Pv), and PG6 is Mesyl (Ms); the compound (9B) obtained by the process of the invention includes compound of formula (9B1):

Accordingly, a process for preparing a compound of formula (9B1) and its conversion according to the present invention is exemplified in Scheme B l.

Scheme Bl

The compounds of Formula 6B1 and 9B1 are hitherto unreported intermediates useful in the process for the preparation of halichondrin B analogs as described herein.

Intermediate (12B1) obtained by the process of the present invention is converted to Eribulin by using methodology known in the prior art such as WO 2005/118565. In an embodiment, compound of Formula (7B), is prepared by an alternate process which comprises steps of;

a) intermolecular coupling (Alois Furstner coupling) of compound of Formula (16B)

with compound of Formula (

to form compound of Formula (15B);

b) protecting the compound of formula 15B with suitable protecting group to obtain compound (14B);

c) hydrolyzing the ester compound of formula 14B to obtain acid compound (13B); d) converting acid compound of 13B in to /V-Methoxy-/V-methyl (Weinreb) amide compound (7B)

wherein PG3 and PG4 are as defined above and X8 is a leaving group, preferably halide, selected from bromo, chloro and iodo; more preferably iodo.

Compound (7B) is one of the key intermediate in the synthesis of Eribulin.

Accordingly, an embodiment of the process for the preparation of compound of Formula (7B) is as shown in Scheme B2

Scheme B2

The compounds of Formula 13B, 14B and 15B are hitherto unreported intermediates useful in the process for the preparation of halichondrin B analogs as described herein.

In an embodiment, aldehyde of Formula (16B) is subjected to an intermolecular Alois Furstner coupling reaction with halide of Formula (17B). The asymmetric coupling reaction is, preferably carried in the presence of CrC12 and a ligand in the presence of a catalytic amount of vitamin B 12 or cobalt phthalocyanine. The ligand used is preferably selected from sulfonamide ligands such as sulfonamide-A, sulfonamide-B and sulfonamide-C.

The hydroxyl group on compound of Formula (15B) is protected using suitable protecting group to obtain compound of Formula (14B). In an embodiment, protection is carried out by using PvCl, TBSPSC1, TBSC1,TS20, TsCl, TMSOTf or MsCl in presence of a base such as collidine, lutidine or TEA in the presence of suitable solvent.

Compound of Formula (14B) is further hydrolyzed to acid of Formula (13B) by methods known in the art. Examples of such methods include, but not limited to, treatment with NaOH or LiOH in the presence of an alcohol, water or mixture thereof.

The conversion of sterically hindered carboxylic acid of Formula (13B) to N- methoxy-N-methyl amide of Formula (7B) can be efficiently carried out by reaction of N, O-dimethyl hydroxylamine hydrochloride in the presence of a coupling reagent. A preferred coupling reagent is EDC.HC1. The major byproduct in the reaction, N-methoxy-N-methylmethanesulfonamide can be removed by placing the product mixture under vacuum for 15-25 h.

In one preferred embodiment, when X8 is iodo, PG3 is tert-butyldimethylsilyl (TBDMS), PG4 is tert-butylsilyl (TBS); and the compound (7B) obtained by the process of the invention includes compound of formula (7B 1).

Accordingly, a process for preparing a compound of formula (7B1) is exemplified in Scheme B3.

Scheme B3

The compounds of Formula 13B1, 14B1 and 15B 1 are hitherto unreported intermediates useful in the process for the preparation of halichondrin B analogs as described herein.

In yet another aspect, the invention provides an improved batch process for the synthesis of compound of Formula (5C):

5C wherein each of PGs, PGs, PGio, PGn, and PG12, are independently H or Cl -6 alkyl or a hydroxyl protecting group; and X7 is a leaving group.

In certain embodiments, one or both of PGx and PG9 of Formula (5C), taken with the oxygen atom(s) to which they are bound, are silyl ethers or aryl alkyl ethers. For example, one or both of PGs and PG9 are TBS or benzyl, or both PGx and PG9 are TBS;

In certain embodiments, each of PGs and PG9 are independently FI or Cl -6 alkyl; or PGs and PG9, together with the oxygen atoms to which they are attached, form a diol protecting 5- to 6-membered heterocyclic ring, which is optionally substituted with Cl -4 alkyl groups. Diol protecting groups are well known in the art and include cyclohexylidene and benzylidene diol protecting group.

In one embodiment R is H, Cl-6 alkyl or Cl-6 haloalkyl. In a further embodiment R is Cl-6 alkyl. In a preferred embodiment R is methyl.

Ri and R2 each independently is H, -CH2OR3 or -CFhSCkAr, or Ri and R2 together form =CFl2S02Ar, wherein R3 is IT or a hydroxyl protecting group; and Ar is an aryl group.

In certain embodiments, one, two, or three ofPGio, PG11, and PG12 ofFormula (5C), taken with the oxygen atom(s) to which they are bound, are silyl ethers or arylalkyl ethers. For example, one, two, or three of PG10, PG11, and PG12 of Formula (5C) are t-butyldimethylsilyl (TBS) or benzyl, or all of PGs, PG9, and PG10 of Formula (VIII) are t-butyldimethylsilyl (TBS). In other embodiments, X3 is a halogen, (Cl- C6)alkyl sulfonate, (C6-C10 aryl or Cl -C6 heteroaryl) sulfonate, (C6-Cl5)aryl(Cl- C6)alkylsulfonate, or (Cl- C6)heteroaryl (Cl-C6)alkyl sulfonate. Specific examples of X ₃ include iodide, mesylate, toluenesulfonate, isopropylsulfonate, phenyl sulfonate, nitro-phenyl sulfonate (nosylate), and bromo-phenyl sulfonate (brosylate ), and benzylsulfonate.

In certain embodiments, one or both of PGio, PGn, and PG12 of Formula (5C), taken with the oxygen atom(s) to which they are bound, are independently selected from esters, ethers, silyl ethers, alkyl ethers, arylalkyl ethers, and alkoxyalkyl ethers. Examples of such esters include formates, acetates, carbonates, and sulfonates. Specific examples include formate, benzoyl formate, chloroacetate, trifluoroacetate, methoxyacetate, triphenylmethoxyacetate, p-chloro phenoxyacetate, 3-phenylpropionate, 4-oxopentanoate, 4,4-( ethylenedithio )pentanoate,

pivaloate (trimethylacetyl), crotonate, 4-methoxy-crotonate, benzoate, p- benylbenzoate,

2,4,6-trimethylbenzoate, carbonates such as methyl, 9-fluorenylmethyl, ethyl, 2,2,2-trichloro ethyl, 2-(trimethylsilyl)ethyl, 2-(phenylsulfonyl)ethyl, vinyl, allyl, and p-nitrobenzyl.

Examples of such silyl ethers include trimethyl silyl, tri ethyl silyl, t- butyldimethyl silyl, t-butyldiphenylsilyl, triisopropylsilyl, and other trialkylsilyl ethers. Alkyl ethers include methyl, benzyl, p-methoxybenzyl, 3,4- dimethoxybenzyl, trityl, t-butyl, allyl, and allyloxycarbonyl ethers or derivatives. Alkoxyalkyl ethers include acetals such as methoxymethyl, methylthiom ethyl, (2- methoxyethoxy)methyl, benzyloxymethyl, beta(trimethylsilyl) ethoxymethyl, and tetrahydro pyranyl ethers. Examples of arylalkyl ethers include benzyl, p- methoxybenzyl (MPM), 3,4-dimethoxybenzyl, o-nitrobenzyl, pnitrobenzyl, p- halobenzyl, 2,6-dichlorobenzyl, p-cyanobenzyl, 2- and 4-picolyl.

For example, in other embodiments, one, two, or three of PG10, PG11, and PG12, are t-butyldimethylsilyl (TBS), benzyl(Bz) or tosyl (Ts), or all of PG10, PG11, and PG12, are t-butyldimethylsilyl (TBS) or tosyl (Ts). In some embodiments PGio and PGn , together with the oxygen atoms to which they are attached, form a diol protecting 5- to 6-membered heterocyclic ring, which is optionally substituted with Cl-4 alkyl groups. In other embodiments, PGio and PGn are taken together to form a cyclohexylidene protecting group.

In some embodiments X7 is halogen, such as iodide. In other embodiments, X7 is (Cl- C6)alkylsulfonate, (C6-C10 aryl or C1-C6 heteroaryl)sulfonate, (C6- C15)aryl(Cl- C6)alkyl sulfonate, or (Cl -C6)heteroaryl(C 1 -C6)alkylsulfonate. Specific leaving groups include mesylate, toluenesulfonate, isopropylsulfonate, phenyl sulfonate, or benzyl sulfonate.

In an embodiment, compound of Formula (3C)

Int- 3C

is coupled with compound of Formula (4C)

Int 4C

in the presence of a base and a suitable solvent, similar to those as noted herein and disclosed in US Patent Number 6,214,865 B 1 (incorporated herein by reference) to form an intermediate alcohol. This is followed by oxidation of the alcohol using reagents to give the compound of Formula (5C). Preferably, compound of Formula (4C) is treated with n-butyllithium then with the aldehyde of Formula (3C). The resulting diol intermediate is then oxidized with Dess-Martin reagent to form the ketone-aldehyde intermediate of Formula (5C) as shown in Scheme C.

Scheme C

In one preferred embodiment, R is methyl, Ri and R2 together form CFhSC Ph, PGs, PG9, PG10, PG11, and PG12 together with the oxygen atoms to which they are attached, form a TBS ether; and X7 is iodide; the compound (5C) obtained by the process of the invention includes compound of formula (5C1):

In a preferred embodiment compound (4C1) is converted to compound (5C1) as shown in Scheme Cl. Scheme Cl

Preferably, intermediate (4C1) is dissolved in an inert solvent such as THF or DME and cooled to about 5°C to about -10°C. A solution of n-butyllithium is added to the dry solution and the reaction mixture is further chilled to about -60°C to about -70°C. Then reacted with intermediate (3C1) and further stirred for about 30 mins to about 60 mins. The saturated aqueous ammonium chloride was added, and the mixture extracted with non polar solvent such as ethyl acetate, toluene, or hexane.. The usual work-up, followed by chromatography gave 80% of a solid.

The process of the present invention is advantages as it not only improves the yield from 20-30% to 70% as reported in the prior art US 8,148,554 B2. This forms one aspect of the present invention. The intermediate (5C1) is isolated in the solid form as against reported oily form, which makes work up and storage feasible on industrial scale. This forms another aspect of the present invention. The isolated solid optionally purified on large scale before taking up for the next step. The intermediate 5C1 is one of the key intermediate in the synthesis of Eribulin.

Intermediates 16A1, 12B and 5C1 obtained by the processes of the present invention are converted to Eribulin by using methodology known in the prior art such as WO 2005/118565, as shown in scheme D 1.

Scheme D1

Eribulin obtained by using intermediates is free of many impurities.

Eribulin obtained by the process of the present invention may subsequently be converted to the corresponding pharmaceutically accepted salts by reacting with corresponding acid in suitable solvents.

The pharmaceutically acceptable salt of eribulin prepared according to the present invention, preferably having purity at least 98%, more preferably at least 99%, are selected from inorganic acid salt or organic acid salt. The inorganic acid salts may be selected from but not limited to hydrochloride, sulfate, hydrobromide, hydroiodide, nitrate, bisulfate and phosphate salts.

The organic acid salts may be selected from but not limited to ascorbate, malonate, citrate, cinnamate , malate, isonicotinate, acetate, lactate, salicilate, tartrate, pantotenate, ascorbate, succinate, stearate maleate, fumarate, gluconate, saccharate, formate, benzoate, glutamate, mesyalte, esylate, benzenesulfonate , p- toluenesulfonate, pamoate, lactate, oleate, tannate and oxalate salts. Preferably, eribulin is converted to mesylate salt.

While emphasis has been placed herein on the specific steps of the preferred process, it will be appreciated that many steps can be made and that many changes can be made in the preferred steps without departing from the principles of the invention. These and other changes in the preferred steps of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

The details of the invention given in the examples which are provided below are for illustration only and therefore these examples should not be construed to limit the scope of the invention.

Examples

Example 1 : Preparation of Compound (2A1):-

1 A1 2A1

To a solution of 4-Methoxybenzyl-2,2,2-trichloroacetimidate (18 g, 76 mmol, 1.5 eq) in dichloromethane (50 ml) at room temperature, was added (S)-methyl 3- hydroxy-2-methylpropanoate (5 g, 42 mmol, 1.5 eq) followed by camphor sulfonic acid (CSA) (176 mg, 0.76 mmol, 0.018 eq). The reaction mixture was stirred at ambient temperature for 18 hr, and then diluted with Dichloromethane (20 ml). The reaction mixture was washed with sat. aqueous NaHC03 (40 mL), followed by brine (40 mL), dried over sodium sulphate and evaporated under reduced pressure. The product was purified by column chromatography by using SiCh and eluted with Ethyl acetate/ hexane. The collected fractions were evaporated to give a compound 2A1 (9 g, 90%) [alpha 25 D] = +7.5 deg (c = 1.0 in CHC13).

Example 2 : Preparation of Compound (3A1):-

2A1 3A1

Compound 2A1 (5 g, 21 mmol, 1.0 eq) was taken in THF (50 ml) and cooled to - 78°C by using dry ice and Acetone. A solution, of Diisobutylaluminum hydride 25 wt. % in toluene ( DIBAL-H) (26 ml, 46 mmol, 2.2 eq) was added dropwise over 45 min and stirred further for 60 min at same temperature. Upon completion, the reaction mixture was quenched with sodium potassium tartrate solution (50 ml) and stirred vigorously for 3 hrs. The organic layer was separated, dried over Na2S04 and evaporated under reduced pressure. The product was purified by column chromatography by using SiCk and eluted with Hexane / Ethyl acetate mixture. The collected fraction evaporated to give a compound 3Al(Yield 3.5, 80%).

Example 3 : Preparation of Compound (4A1)>

3A1 4A1

To a solution of (Methoxy Methyl) Triphenyl Phosphonium Chloride (12.3 g, 36 mmol, 2.5 eq) in anhydrous THF (50 ml) under nitrogen atmosphere was added a solution of potassium tert- butoxide 1M solution in tetrahydrofuran (36 ml, 36 mmol, 2.5 eq), over 30- 45 min at 0-5° C. The reaction temperature was raised to 22-25° C and stirred further for 2 hr. The reaction mixture was cooled to 0-5° C. A solution of Compound 3A1 (3 g, 14.4 mmol, 1 eq) in tetrahydrofuran (10 ml) was added slowly over 30-45 min at 0-5° C. The reaction temperature was raised to 22-

25° C and stirred further for 2 h. The reaction mixture was cooled to below l5°C and diluted with Methyl tert-butyl ether (50 ml) followed by D.I water (50 ml) at l0-l5°C. The organic layer was separated and aqueous layer was extracted with Methyl tert-butyl ether (50 ml). The combined organic layers were dried over sodium sulphate and evaporated under vacuum at 35-40°C. The product was purified by column chromatography by using SiCh. With Hexane / Ethyl acetate mixture. The collected fractions evaporated to give a compound 4A1 (Yield 2.1 g, 61%).

Example 4 : Preparation of Compound (5A1):-

4A1 5A1

A solution of compound 4A1 (5 g, 21.2 mmol, 1 eq) in a mixture of acetic acid (25 ml) and water (3 ml) was stirred at 25°C for 16 h. The reaction mixture was diluted with MTBE (50 ml), washed with water (20 ml), saturated aqueous sodium bicarbonate (20 ml) and brine (20 ml), dried over sodium sulphate and evaporated under vacuum at 35-40°C. The product was purified by column chromatography by using S1O2 and eluted with Hexane / Ethyl acetate mixture. The collected fractions evaporated to give a compound 5Al(Yield 3.5 g, 74%).

Example 5: Preparation of Compound (7A1):-

Sulfonamide Ligand (666 mg, 45 mmol, leq) and Co phthalocyanine (13 mg, 0.022mmol, 0.01 eq) were weighed outside a glove box and put in a flask. In a glove box, proton sponge (481 mg, 2.25 mmol, leq), CrCl2 (275 mg, 2.25 mmol, 1 eq) and DME (21 ml) were added and the resulting mixture was then stirred at room temperature for 1 h. To the resulting green solution were added LiCl (567 mg, l3.5mmol, 6.0 eq), Mn powder (729 mg, 13.5 mmol, 6.0 equiv), Zr(Cp)2Cl2 ( 3.94 g, 13.5 mmol, 6.0 equiv) and a solution of Compound 5A1 aldehyde (222 mg, 2.25 mmol, 1 eq) and diiodide 6 (410 mg, 4.5 mmol, 2.0 eq) in DME (2 ml) successively. The reaction mixture was stirred at room temperature in a glove box for 16 h. The reaction mixture was evaporated and the slurry was loaded in to the column chromatography and eluted with Ethyl acetate : hexane to provide alcohol compound 7A1 (Yield 150 mg, 54%).

Example 6: Preparation of Compound (8A1):-

7A1 8A1

Compound 7A1 (4g, l4.3mmol, leq) was stirred in MTBE (40 ml) under nitrogen atmosphere. To the reaction mixture was added 2,6-lutidine (4.1 ml, 36mmol, 2.5 eq) and then cooled to 0-5°C. To the reaction mixture was added drop wise TBSOTf (5.6 g, 21 45mmol, 1 5eq ) at 0°C. The reaction mixture was further stirred for 30 min at 0-10 °C, then gradually warmed to 23 °C for 16 h. MeOH (2 ml) and water (20 ml) were added drop wise sequentially to the reaction mixture and stirred for 30 min. After phase separation, the upper layer was washed with 0.5N aqueous hydrochloric acid (2X 20 ml), 5 % NaCI solution. (20 ml), 5 % NaHC03 Solution. (20 ml), 5 % NaCI solution (20 ml), and 5 % NaCI solution (20 ml), respectively. The upper organic layer was concentrated under reduced pressure to afford the crude compound 8 A1. The crude product was purified by column chromatography on 230-400 mesh silica gel, and eluted with ethyl acetate: hexane mixture. The collected fractions were evaporated under reduced pressure to give a pure compound8Al (Yield 4.2 g, 75%).

Example 7: Preparation of Compound (9A1):-

9A1

A solution of compound 8A1 (5g, 12.75 mmol, leq) was taken in dichloromethane (50 ml) and the mixture was cooled to -78° C. Purged ozone gas at -78° C until the slight blue colour appeared. Then quenched with Triphenyl phosphine (3.6 g, Mmmol, l . leq) and stirred at room temperature for 16 hr. Dichloromethane was evaporated and the residue was treated with 5% ethyl acetate: hexane (100 ml) stirred for 2 h. Triphenyl phosphine oxide was removed by filtration and the filtrate was evaporated to obtain crude. The crude product was purified by column chromatography by using 230-400 mesh silica gel, and eluted with ethyl acetate: hexane mixture. The collected fractions were evaporated under reduced pressure to give a compound 9A1 (Yield 4.5 g, 90%).

Example 8: Preparation of Compound (12A1):-

^{1 0A1} 1 1A1 12A1

Anhydrous chromous chloride (4.26 g, 35 mmol, 4.6 eq) was taken in clean dry RB under argon atmosphere in glove box. A solution of Sulphonamide ligand (10.34 g, 35 mmol, 4.6 eq) in dry THF (1.5 ml) was added Followed by triethylamine (4.9 ml, 35 mmol, 4.6 eq). The resulting light green solution was heated at 35°C for 2 hr. Deep green reaction mixture was cooled to 0°C, NiC12 (0.1 g, 0.76 mmol, 0.1 eq) was added to the reaction mass under argon atmosphere followed by a solution of compound 9A1 (3.0 g, 7.6 mmol, 1.0 eq) and compound 10A1 (4.7 g, 35 mmol, 1.2 eq) in dry THF (21 ml). The reaction mixture was allowed to stir at room temperature for 16 hr, diluted with MTBE (100 ml) and filtered over celite pad. The filtrate was concentrated under reduced pressure to obtain the crude compound 11 Al and then passed through a short pad of silica gel. The solvent was evaporated and the crude product was taken for next step without purification.

A solution of compound 11 Al (crude) in THF (45 mL) in a clean and dry RBF , covered with aluminum foil, was cooled to 0-5°C. Then silver(I) oxide (2.61 g, 11.4 mmol, 1.5 eq) and silver trifluoromethanesulfonate (3.9 g, 15.2 mmol, 2 eq) were added. And the resultant black suspension was stirred for 12 h at room temperature. The reaction mixture was cooled to 0-5°C, quenched with triethylamine (4.0 mL), diluted with EtOAc, and filtered through a pad of Celite. The solvent was evaporated and the residue was purified by flash column chromatography on silica gel to give cyclized compound 12A1 (Yield: 2.9 g, 50 %). Example 9: Preparation of Compound (13A1):-

12A1

13A1

To a cooled solution of compound 12A1 (2g, 2.6 mmol, leq)) in a mixture of acetonitrile and water (19: 1, 90 mL), was added solid ceric ammonium nitrate (7.3 g, 13.42 mmol, 5eq) in one portion at 0°C. The resulting reaction mixture was allowed to stir at room temperature for 6 hr. The reaction mixture was diluted with EtOAc and saturated NaHC03 was added. The resulting suspension was stirred for 30 min at room temperature, and then filtered through a pad of celite. The organic layer was separated and washed once with brine. The organic layer was dried over Na2S04 and evaporated under vacuum below 35°C. The crude product was purified by column chromatography by using S1O2 and eluted with Hexane / Ethyl acetate mixture. The collected fractions evaporated to give a compound 13A1 (Yield 1.2 g, 71%).

Example 10: Preparation of Compound (14A1):-

13A1

14A1

Compound 13Al(l.O g, 1.6 mmol, 1 eq) was dissolved in dichloromethane (15 ml) under nitrogen atmosphere. Dess-Martin periodinane ((1.1 g, 2.4 mmol, 1.5 eq) was added portion wise at 20-30°C. The reaction mixture was stirred at 20-30°C for 2 hr. Reaction mixture was quenched with 5 wt% , aqueous NaHC03 solution (50 ml) followed by DCM (50 ml) at room temperature and stirred for 30-40 min. The organic layer was washed with 5 wt% NaHC03 solution, followed by mixture of 5 wt% NaHC03 solution and 20 wt% Na2S03 solution. The organic layer was separated and the aqueous layer was extracted with DCM (20 ml). The organic layer was separated, dried over Na2S04 and evaporated under vacuum below 35°C. The product was purified on column chromatography by using S1O2 and eluted with Hexane / Ethyl acetate mixture collected fractions and evaporated to give a compound 14A1 (Yield 800 mg, 80%).

Example 11 : Preparation of Compound (15A1):

14A1 ^{1 5A1}

To a stirred solution of compound 14A1 (0.5 g, 0.77 mmol, 1) in dry THF(25 ml), methyl magnesium bromide (3 M), ( 1.0 ml, 3.0 mmol, 4eq) solution was added drop wise at -20°C under argon atmosphere and the reaction mass was stirred at same temperature for 15 min. The reaction mixture was quenched with sat ammonium chloride solution (20 ml) and extracted with ethyl acetate (3 x 100 ml), washed with water(l0 ml) followed by brine (10 ml), dried over anhydrous sodium sulphate and evaporated under reduced pressure to afford the crude compound which was purified by column chromatography by using Si02 .Compound eluted with ethylacetate in hexane mixture to give compound 15A1 (yield 400 mg, 78%). Example 12: Preparation of Compound (3B1):-

1B1 2B1 3B1

To a stirred solution of compound 1B1 (8.0 g, 24 mmol) in THF-H20 (6: 1, 60 ml : 10 ml) was added osmium tetroxide (14 ml, 1% t-BuOH solution) followed by NMO (5.62g, 48 mmol) at 0°C under argon atmosphere. After completion of the reaction, sodium periodate (28 g, 72 mmol) was added at 0°C and the resultant mixture was stirred at room temperature for 6 hrs. Reaction mixture was diluted with water (500 ml), organic part was extracted with ethyl acetate (2x 600 ml), washed with water (500 ml) followed by brine (200 ml), dried over anhydrous sodium sulphate and evaporated under reduced pressure to get the crude compound 3B1, which was purified by column chromatography by using silica gel, eluted ethyl acetate in hexane to afford the desired compound 3B1 (5.8 g, 75 %) as yellow oil.

Example 13 : Preparation of Compound (5B1):-

4B1 5B1

To a solution of compound 4B1 (10.0 g, 26 mmol) in CH2C12 (130 ml) at 0°C was added dropwise B-iodo-9-BBN (Aldrich, 28 ml, 1.0 M in hexanes). The reaction mixture was stirred for 30 min at 0°C before addition of acetic acid (3.3 ml, 52 mmol). The reaction was allowed to stirred further for 0.5 h at 0°C. The reaction mixture was titrated to red with 30% aqueous hydrogen peroxide and then to colourless with aqueous sodium thiosulfate. The organic layer was washed with saturated aqueous sodium bicarbonate (3x100 ml), dried over anhydrous Na2S04 and concentrated under reduced pressure. The crude product was purified on flash column chromatography and eluted with ethyl acetate in hexane to give compound 5B1 (Yields: l l .O g, 83%)

Example 14: Preparation of Compound (7B1):-

Anhydrous chromous chloride (11 g, 89.83 mmol) was taken in clean dry RB under argon atmosphere in glove box. R- ligand (26.5 g, 89.83 mmol) was dissolved in dry THF (300 ml) was added, followed by triethylamine (12.9 ml, 89.83 mmol). To ensure ligand-Chromium complex formation the resulting light green solution was heated at 35°C for 2 hr and reaction mass turned dark green in colour. Deep green reaction mass was cooled to 0°C and NiC12 (0.13 g, 1.0 mmol) was added to the reaction mass under argon atmosphere followed by addition of compound 5B1 (10.0 g, 19.53 mmol) and compound 3B1 (8.4 g, 25.39 mmol) in dry THF(60 ml). The reaction mass was allowed to stir at room temperature for 16 hrs (overnight), diluted with THF (100 ml) and filtered over celite pad. Collected filtrate was concentrated under reduced pressure to obtain the crude compound 6B 1 and then passed through a short pad of silica gel. The solvent was evaporated and used in the next step without purification.

Example 15: Preparation of Compound (8B1):-

To a stirred solution of compound 7B1 (10.0 g, 14.6 mmol) in dry THF(l00 ml), methyl magnesium bromide (3 M), (19.5 ml, 58.6 mmol) solution was added drop wise at -20°C under argon atmosphere and the reaction mass was allowed to stir at room temperature for 1 hr. Reaction mixture was cooled to 0-5°C, quenched with sat ammonium chloride solution, organic part was extracted with ethyl acetate( 3 x 100 ml), washed with water followed by brine, dried over anhydrous sodium sulphate and evaporated under reduced pressure to afford the crude compound which was purified on column chromatography by using Si02 and eluted with ethylacetate in hexane mixture to give compound 8B1 (yield 6.5 g, 70%).

Example 16: Preparation of Compound (9B1):-

To a stirred solution of compound 8B1 (18 g, 28.3 mmol) in absolute ethanol (360 ml), Triethyl amine (36 ml, 8.8 mmol) followed by hydrazine hydrate (18 ml) were added. Then the Reaction mixture was heated to 60-65° C for 2.5 hr. Reaction mixture was evaporated under vacuum. The residue was diluted with dichloromethane (500 ml) , washed with water (2X100 ml) followed by brine solution(100 ml). The organic layer was dried over MgS04, filtered, and concentrated to give Intermediate hydrazone. This was taken onto the next step without further purification.

A solution of Intermediate hydrazone in diethyl ether (3.8 lit) was cooled to 0°C. Triethyl amine (212 ml), followed by Iodine (16.4 g, in 2.5 lit of diethylether) were added slowly over period of 1-1.5 hr maintaining internal temperature below 5°C. The reaction mixture was slowly warm to room temperature and stirred for 30min. Reaction mixture was quenched with DI water (2 Lit). Organic layer was washed with 5% sodium thiosulphate solution (2X1 lit), DI water (1.5 Lit), Brine solution (1.5 Lit) and dried over anhydrous Na>SO-i, and evaporated under reduced pressure. Crude was purified by Si02 by using Ethyl acetate: Hexane mixture as an eluent to give compound no (9B1) (Yield 13 g, 62%).

Example 17: Preparation of Compound (10B1):-

9B1 10B1

To a stirred solution of compound 9B 1 (12.5 g, 0.130 mmol) in dry methanol (4 ml), was added IP A- HC1 (4 M) (12 ml) drop wise at 0°C under argon atmosphere and the reaction mixture was stirred at RT for 3 hr. After complete conversion of the SM, solid sodium bicarbonate was added at 0°C in lots to the reaction mixture until pH-6. The reaction mixture was filtered through celite pad. The filtrate was concentrated under reduced pressure to obtain the crude compound (10B1) which was purified by Si02 by using Methanol in dichloromethane mixture as a eluent to give compound no (10B1) (Yield 5.3 g, 84%). Example 18: Preparation of Compound (11B1):-

To a stirred solution of compound 10B1 (2 g, 5.0 mmol) in dry DCM (20 ml), 2,4,6- Collidine (8.06 ml, 60.0 mmol) and DMAP (200 mg, 1.63 mmol) were added at 0°C under argon atmosphere and the reaction mixture was stirred at 0°C for 30 min. Pivaloyl chloride (2.48 ml, 20.2 mmol) was added and the reaction mixture was stirred at RT for 45 min under argon atmosphere. The reaction mixture was diluted with DCM (80 ml) and quenched with water (20 ml). The organic layer was washed with 1N HC1 (30 ml) followed by saturated sodium bicarbonate solution (30 ml), water (30 ml) and brine(30 ml), dried over anhydrous sodium sulphate, concentrated and purified by column chromatography by using Si02, eluted with ethyl acetate in hexane mixture to give compound 11B 1 (yield 2.0 g, 83%).

Example 19: Preparation of Compound (12B1):-

To a stirred solution of compound 1 IB 1 (1.2 g, 5.0 mmol) in anhydrous THF (30 ml), were added triethylamine (1.74 ml, 12 5 mmol) and DMAP (120 mg, 0.9 mmol) at 0°C under argon atmosphere. The reaction mixture was stirred at 0°C for 30 min followed by the addition of methanesulfonyl chloride (2.48 ml, 20.2 mmol) and further stirred at 0°C for 30 min under argon atmosphere. The reaction mixture was quenched with DI water (50 ml) and diluted with pet ether (100 ml). The organic layer was separated, washed with DI water (2 X 20 ml) followed by brine (20 ml), dried over anhydrous sodium sulphate and evaporated under reduced pressure to afford the compound 12B1 (yield 1.3 g, 93%).

Example 20: Preparation of Compound (5C1)

Inter-4 sulfone (4C1) (0.5 g, 0.58 mmol, 1 eq) was dissolved in anhydrous THF (4 ml) under nitrogen atmosphere and cooled to 0-5°C. A solution of n-BuLi (1.6 M solution in hexanes, 0.9 ml, 1.45 mmol, 2.5 eq) was added to the solution at 0-5°C over 20 min and stirred the reaction mixture for same temperature for another 15 min. The reaction mixture further Cooled to -70°C, then added Int-3 aldehyde (3C1) (0.48 g, 0.64 mmol, 1.1 eq) via syringe pump over 45 min. resulting mixture was stirred for 30 min. The reaction mixture was quenched by an addition of 14 wt% aqueous NH4C1 (10 ml), followed by additions of water (20 ml) and MTBE (30 ml). Separated the organic layer, washed with water (20 ml) dried over sodium sulphate and evaporated under reduced pressure. Crude product was purified by column chromatography by using SiCh and eluted with Hexane / Ethyl acetate mixture to give a (5C1) (Yield 750 mg, 80%).

Example 21 : Preparation of Compound (15B1)

Sulfonamide Ligand (169 mg, 0.57 mmol, leq) and Co phthalocyanine (3.2 mg, 0.0057 mmol, 0.01 eq) were weighed outside a glove box and put in a flask. In a glove box, proton sponge (122 mg, 0.57 mmol, leq), CrC12 (70 mg, 0.57 mmol, 1 eq) and DME (18 ml) were added and the resulting mixture was then stirred at room temperature for 1 h. To the resulting green solution were added LiCl (145 mg, 3.42 mmol, 6.0 eq), Mn powder (188 mg, 3.42 mmol, 6.0 eq), Zr(Cp)2C12 (1.0 g, 3.42 mmol, 6.0 eq) and a solution of aldehyde compound (16B1) (250 mg, 0.57 mmol, 1 eq) and iodide (17B 1) (261 mg, 1.14 mmol, 2.0 eq) in DME (2 ml) successively. The reaction mixture was stirred at room temperature in a glove box for 16 h. The reaction mixture was evaporated and the slurry was loaded in to the column chromatography and eluted with Ethyl acetate : hexane to afford alcohol compound (15B1) (Yield 150 mg, 50%).

Example 22: Preparation of Compound (14B1)

Compound (15B 1) (200 mg, 0.37 mmol, leq) was stirred in MTBE (20 ml) under nitrogen atmosphere. To the reaction mixture was added 2,6-lutidine (0.11 ml, 0.92 mmol, 2.5 eq) and then cooled to 0-5°C. To the reaction mixture was added drop wise TBSOTf (0.15 g, 0.55 mmol, l.5eq) at 0°C. The reaction mixture was further stirred for 30 min at 0-10 °C, then gradually warmed to 23°C for 16 h. MeOH (2 ml) and water (20 ml) were added drop wise sequentially to the reaction mixture and stirred for 30 min. After phase separation, the upper layer was washed with 0.5N aqueous hydrochloric acid (2X 20 ml), 5 % NaCI solution. (20 ml), 5 % NaHC03 Solution. (20 ml), 5 % NaCI solution (20 ml), and 5 % NaCI solution (20 ml), respectively. The upper organic layer was concentrated under reduced pressure to afford the crude compound (14B 1). The crude product was purified by column chromatography on silica gel, and eluted with ethyl acetate: hexane mixture. The collected fractions were evaporated under reduced pressure to give a pure compound (14B1) (Yield 0.2 g, 83%).

Example 23 : Preparation of Compound (13B1)

Compound (14B1) (200 mg, 0.3 mmol, leq) was dissolved in methanol : water (5: 1), Li OH (15 mg, 0.6 mmol, 2.0 eq) was added to the reaction mass and then stirred reaction mass at RT for 2 h. After completion of reaction, the reaction mass quenched in a mixture of water : ethyl acetate. The pH of the reaction mass was adjusted to 7 using (0.5M) aq. HC1 solution. Organic layer separated and washed with brine solution. Organic layer dried over sodium sulphate and evaporated under dryness below 35°C to afford a pure compound (15B1) (Yield 0.18 g, 92%).

Example 23 : Preparation of Compound (7B 1)

To a stirred solution of the carboxylic acid (13B1) (200 mg, 0.31 mmol, leq) in CH2CI2 (8 mL), were added 4-dimethylaminopyridine (38 mg, 0.31 mmol, leq), N,O-dimethyl hydroxyamine hydrochloride (30 mg, 0.31 mmol, leq), N- methylmorpholine (31 mg, 0.31 mmol, leq) and N-(3-dimethylaminopropyl)-N'- ethyl carbodiimide hydrochloride (48 mg, 0.31 mmol, leq) consecutively at room temperature. The reaction mixture was left stirring for 18 h. then washed with an 10% aqueous citric acid solution (3x 10 mL), brine (10 mL), 5% aqueous NaHCCb solution (3 x 10 mL) and brine (10 mL). The organic layer was dried (Na2S0 ₄ ) and concentrated under reduced pressure. The amide was purified by flash chromatography eluting with the mixture of EtOAc: Hexane to afford the desired product compound (7B1) (Yield 0.13 g, 62%).

Example 24: Preparation of Compound ( 17B 1)

To a stirred solution of Compound (1A1) (1.0 g, 8.47 mmol, leq) in CH2CI2 (15 V) were added p-Toluenesulfonyl chloride (1.77 g, 9.3 mmol, 1.1 eq), Triethylamine (2.4 mL, 16.94 mmol, 2 eq) and DMAP (52 mg, 0.42 mmol, 0.05 eq) at 0°C. The reaction mixture was stirred for 2.5 h at room temperature. The completion of reaction was checked by TLC monitoring. Upon completion, the reaction was quenched into water and stirred for 15 mins. The layers were separated and the organic layer was washed with brine solution, dried over Na2S04 and concentrated to give the crude product which was purified by flash chromatography using ethyl acetate: Hexane mixture to give the pure Compound (2A2) (Yield 1.5 g, 65%). To a stirred solution of Compound (2A2) (1.0 g, 3.6 mmol, leq) in ACN (20 ml) at room temperature was added Sodium Iodide (1.08 g, 7.2 mmol, 2 eq). The reaction mixture was heated to 70°C and maintained for 16 h. The completion of reaction was checked by TLC. Upon completion, the reaction mixture distilled completely, diluted with water (20 ml) and Ethyl acetate (40 ml) and stirred for 15 mins. The layers were separated and the organic layer was dried over Na ₂ S04 and concentrated to give the crude product which was purified by flash chromatography by using ethyl acetate : Hexane to give the pure Compound (17B1) (Yield 0.6 g, 72%).