Entecavir synthesis method and intermediate compound thereof

1. A method for preparation of the compound of formula 1,

comprising the following steps:

reacting compound 4

with 2-protected amino-6-substituted purine compound 5

to give the coupling reaction product 6

wherein

R 1 and R 2 , which are the same or different, are independently selected from hydroxy-protecting groups of the following Groups (i) to (iii):

(i) R 1 and R 2 , independent of each other, are selected from alkyl, halo-alkyl, benzyl, t-BuMe 2 Si, t-BuPh 2 Si, (i-Pr) 3 Si or Et 3 Si; or

(ii) R 1 and R 2 , independent of each other, are selected from t-BuMe 2 Si, t-BuPh 2 Si, benzoyl, tetrahydropyran-2-yl, benzoyl in which the phenyl ring bears substituent(s), and biphenyl-4-formyl, provided that R 1 and R 2 are not both t-BuMe 2 Si;

R and R′, which are the same or different, are independently selected from hydrogen, alkoxycarbonyl or aralkoxycarbonyl, provided that R and R′ are not both hydrogen; X is halo, alkoxy, halo-alkoxy or aralkoxy;

Thereafter when R 1 and R 2 are both acyl protective groups or neither of them is acyl protective group, removing hydroxy-protecting groups from compound 6, to give compound 7

wherein X, R 1 , R 2 , R and R′ are defined as above;

Thereafter hydrolysis of compound 7 to give the compound of formula 1

or

when neither of R 1 and R 2 is acyl protective group, deprotecting compound 6 while hydrolysis in one-pot manner, to directly yield the compound of formula 1

wherein X, R 1 , R 2 , R and R′ are defined as above, or

when one, but only one of R 1 and R 2 is acyl protective group, deprotecting compound 6 to give compound 8

which is then hydrolyzed to give compound 1

or is converted to compound 7 followed by hydrolysis to give compound 1.

2. The method according to claim 1 , wherein R 1 and R 2 , which are the same or different, are independently selected from the group consisting of alkyl, halo-alkyl, benzyl, t-BuMe 2 Si, t-BuPh 2 Si, (i-Pr) 3 Si or Et 3 Si.

3. The method according to claim 1 , wherein R 1 and R 2 , which are the same or different, are independently selected from the group consisting of t-BuMe 2 Si, t-BuPh 2 Si, benzoyl, tetrahydropyran-2-yl, benzoyl in which the phenyl ring bears substituent(s), and biphenyl-4-formyl; provided that R 1 and R 2 are not both t-BuMe 2 Si.

4. The method according to claim 1 , wherein the reaction of compound 4 with 5 is performed in the presence of a Mitsunobu reaction reagent, in a non-protonic solvent.

5. The method according to claim 1 , wherein deprotection of compound 6 is performed in the presence of an acid or a base or a quaternary ammonium salt containing fluorinion or potassium carbonate or an alkoxide.

6. The method according to claim 1 , wherein, said hydrolysis of compound 7 is performed under acid or basic condition in water or in a mixture of water and organic solvents.

7. The method according to claim 1 , wherein when neither of R 1 and R 2 is acyl protective group said deprotection and hydrolysis of compound 6 is performed in the presence of hydrohalogen acid, in an appropriate organic solvent or a mixture of said solvent and water.

8. The method according to claim 1 , wherein when neither of R 1 and R 2 is acyl protective group, acyl protective groups are cleaved in the presence of a base.

9. The method according to claim 1 , comprising the following steps:

reacting compound 4 with 2-protected amino-6-substituted purine compound 5 in the presence of Ph 3 P/EtO 2 CN═NCO 2 Et or Ph 3 P/i-PrO 2 CN═NCO 2 i-Pr, in a non-protonic solvent, to give the coupling reaction product 6;

removing hydroxy-protecting groups from compound 6, in the presence of tetrabutylammonium fluoride (TBAF) or hydrochloric acid, to give compound 7;

hydrolysis of compound 7 in the presence of hydrochloric acid, in tetrahydrofuran, to give the compound of formula 1.

10. The method according to claim 1 , wherein the compound of formula 6 is one wherein either both of R 1 and R 2 are acyl protective groups or neither is an acyl protective group.

11. The method according to claim 1 , wherein the compound of formula 6 is one wherein neither of R 1 and R 2 is an acyl protecting group and compound of formula 6 is deprotected and hydrolized in one-pot manner.

12. The method according to claim 1 , wherein the compound of formula 6 wherein either of R 1 or R 2 is an acyl protecting group.

13. The method according to claim 1 , wherein the compound of formula 7 is hydrolyzed to produce the compound of formula 1.

14. A compound having the following formula:

wherein

R 1 and R 2 , which are the same or different, are independently selected from hydrogen or hydroxy-protecting groups of the following Groups (i) to (iii):

(i) R 1 and R 2 , independent of each other, are selected from alkyl, halo-alkyl, benzyl, t-BuMe 2 Si, t-BuPh 2 Si, (i-Pr) 3 Si or Et 3 Si, or

(ii) R 1 and R 2 , independent of each other, are selected from t-BuMe 2 Si, t-BuPh 2 Si, benzoyl, tetrahydropyran-2-yl, benzoyl in which the phenyl ring bears substituent(s), and biphenyl-4-formyl, provided that R 1 and R 2 are not both t-BuMe 2 Si; or

(iii) R 1 and R 2 together with the five-member carbocycle to which they are attached form one of the following fused ring systems:

wherein R 3 is hydrogen atom, C 1-6 alkyl, phenyl or substituted phenyl in which the substituent on said phenyl is selected from methoxy, ethoxy, halo, phenyl and nitro; R 4 and R 5 , which are the same or different, are independently selected from C 1-6 alkyl or aryl; wherein the symbol * represents the attachment point through which said fused ring is attached to the remaining moiety of the molecule;

R and R′, which are the same or different, are independently selected from hydrogen, alkoxycarbonyl or aralkoxycarbonyl, provided that R and R′ are not both hydrogen; X is halo, alkoxy, halo-alkoxy or aralkoxy.

15. The compound according to claim 14 , wherein R 1 and R 2 , independent of each other, are selected from t-BuMe 2 Si, t-BuPh 2 Si, benzoyl, tetrahydropyran-2-yl, benzoyl in which the phenyl ring bears substituent(s), and biphenyl-4-formyl; provided that R 1 and R 2 are not both t-BuMe 2 Si.

16. A compound selected from:

9-[(1S,3R,4S)-4-tert-butyldimethylsilyloxy-3-(tert-butyldimethylsilyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-tert-butyldimethylsilyloxy-3-(tert-butyldimethylsilyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-N-(tert-butyloxycarbonyl)-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-tert-butyldimethylsilyloxy-3-(tert-butyldimethylsilyloxymethyl)-2-methylene-cyclopentyl]-6-methoxy-9H-purine-2-carbamic acid tert-butyl ester;

6-benzyloxy-9-[(1S,3R,4S)-4-tert-butyldimethylsilyloxy-3-(tert-butyldimethylsilyloxymethyl)-2-methylene-cyclopentyl]-9H-purine-2-carbamic acid tert-butyl ester;

6-tert-butyloxy-9-[(1S,3R,4S)-4-tert-butyldimethylsilyloxy-3-(tert-butyldimethylsilyloxymethyl)-2-methylene-cyclopentyl]-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-benzyloxy-3-(benzyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

6-chloro-9-[(1S, 3R,4S)-4-hydroxy-3-hydroxymethyl-2-methylene-cyclopentyl]-9H-purine-2-carbamic acid tert-butyl ester;

6-chloro-9-[(1S,3R,4S)-4-hydroxy-3-hydroxymethyl-2-methylene-cyclopentyl]-N-(tert-butyloxycarbonyl)-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-hydroxy-3-hydroxymethyl-2-methylene-cyclopentyl]-6-methoxy-9H-purine-2-carbamic acid tert-butyl ester;

6-benzyloxy-9-[(1S,3R,4S)-4-hydroxy-3-hydroxymethyl-2-methylene-cyclopentyl]-9H-purine-2-carbamic acid tert-butyl ester;

6-tert-butyloxy-9-[(1S,3R,4S)-4-hydroxy-3-hydroxymethyl-2-methylene-cyclopentyl]-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-3-(tert-butyldimethylsilyloxymethyl)-4-(tetrahydropyran-2-yloxy)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-3-(tert-butyldimethylsilyloxymethyl)-4-(tert-butyldiphenylsilyloxy)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-3-(tert-butyldimethylsilyloxymethyl)-4-(biphenyl-4-formyloxy)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-3-(tert-butyldimethylsilyloxymethyl)-4-benzoyloxy-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-3-(tert-butyldiphenylsilyloxymethyl)-4-(tetrahydropyran-2-yloxy)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-tert-butyldimethylsilyloxy-3-(tert-butyldiphenylsilyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-(biphenyl-4-formyloxy)-3-(tert-butyldiphenylsilyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-(tert-butyldiphenylsilyloxy)-3-(tert-butyldiphenylsilyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-benzoyloxy-3-(tert-butyldiphenylsilyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-benzoyloxy-3-(benzoyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-(tetrahydropyran-2-yloxy)-3-(benzoyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-tert-butyldimethylsilyloxy-3-(benzoyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-(tert-butyldiphenylsilyloxy)-3-(benzoyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-(biphenyl-4-formyloxy)-3-(benzoyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-benzoyloxy-3-(biphenyl-4-formyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-(tetrahydropyran-2-yloxy)-3-(biphenyl-4-formyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-tert-butyldimethylsilyloxy-3-(biphenyl-4-formyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-(tert-butyldiphenylsilyloxy)-3-(biphenyl-4-formyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-(biphenyl-4-formyloxy)-3-(tetrahydropyran-2-yloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-tert-butyldimethylsilyloxy-3-(tetrahydropyran-2-yloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

9-[(1S,3R,4S)-4-(biphenyl-4-formyloxy)-3-(biphenyl-4-formyloxymethyl)-2-methylene-cyclopentyl]-6-chloro-9H-purine-2-carbamic acid tert-butyl ester;

(4aR,6S,7aS)-6-chloro-9-(2,2-di-tert-butyl-5-methylene-hexahydro-cyclopenta[1,3,2]dioxasilin-6-yl)-9H-purine-2-carbamic acid tert-butyl ester;

(2S,4aR,6S,7aS)-6-chloro-9-(2-methyl-5-methylene-hexahydro-cyclopenta[1,3]dioxin-6-yl)-9H-purine-2-carbamic acid tert-butyl ester;

(2R,4aR,6S,7aS)-6-chloro-9-(2-methyl-5-methylene-hexahydro-cyclopenta[1,3]dioxin-6-yl)-9H-purine-2-carbamic acid tert-butyl ester; or

(4aR,6S,7aS)-6-chloro-9-(2-methyl-5-methylene-hexahydro-cyclopenta[1,3]dioxin-6-yl)-9H-purine-2-carbamic acid tert-butyl ester.

17. A compound having the formula 4,

wherein

R 1 and R 2 , which are the same or different, are independently selected from hydroxy-protecting groups of the following Groups (i) to (iii):

(i) R 1 and R 2 , independent of each other, are selected from alkyl, halo-alkyl, benzyl, t-BuMe 2 Si, t-BuPh 2 Si, (i-Pr) 3 Si or Et 3 Si; or

(ii) R 1 and R 2 , independent of each other, are selected from t-BuMe 2 Si, t-BuPh 2 Si, benzoyl, tetrahydropyran-2-yl, benzoyl in which the phenyl ring bears substituent(s), and biphenyl-4-formyl, provided that R 1 and R 2 are not both t-BuMe 2 Si;

(iii) R 1 and R 2 together with the five-member carbocycle to which they are attached form one of the following fused ring systems:

wherein R 3 is hydrogen atom, C 1-6 alkyl, phenyl or substituted phenyl in which the substituent on said phenyl is selected from methoxy, ethoxy, halo, phenyl and nitro; R 4 and R 5 , which are the same or different, are independently selected from C 1-6 alkyl or aryl; wherein the symbol * represents the attachment point through which said fused ring is attached to the remaining moiety of the molecule.

18. The compound according to claim 17 , wherein R 1 and R 2 , independent of each other, are selected from t-BuMe 2 Si, t-BuPh 2 Si, benzoyl, tetrahydropyran-2-yl, benzoyl in which the phenyl ring bears substituent(s), and biphenyl-4-formyl; provided that R 1 and R 2 are not both t-BuMe 2 Si.

19. A compound selected from:

(1R,3R,4S)-4-(tert-butyldimethylsilyloxy)-3-[(tert-butyldimethylsilyloxy)methyl]-2-methylene-cyclopentanol;

(1R,3R,4S)-4-benzyloxy-3-(benzyloxymethyl)-2-methylene-cyclopentanol;

(1R,3R,4S)-4-(tertahydropyran-2-yloxy)-3-(tert-butyldimethylsilyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-(tert-butyldiphenylsilyloxy)-3-(tert-butyldimethylsilyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-(biphenyl-4-formyloxy)-3-(tert-butyldimethylsilyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-benzoyloxy-3-(tert-butyldimethylsilyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-(tetrahydropyran-2-yloxy)-3-(tert-butyldiphenylsilyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-tert-butyldimethylsilyloxy-3-(tert-butyldiphenylsilyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-(biphenyl-4-formyloxy)-3-(tert-butyldiphenylsilyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-(tert-butyldiphenylsilyloxy)-3-(tert-butyldiphenylsilyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-benzoyloxy-3-(tert-butyldiphenylsilyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-benzoyloxy-3-(benzoyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-(tetrahydropyran-2-yloxy)-3-(benzoyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-tert-butyldimethylsilyloxy-3-(benzoyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-(tert-butyldiphenylsilyloxy)-3-(benzoyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-(biphenyl-4-formyloxy)-3-(benzoyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-benzoyloxy-3-(biphenyl-4-formyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-(tetrahydropyran-2-yloxy)-3-(biphenyl-4-formyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-tert-butyldimethylsilyloxy-3-(biphenyl-4-formyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-(tert-butyldiphenylsilyloxy)-3-(biphenyl-4-formyloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-(biphenyl-4-formyloxy)-3-(tetrahydropyran-2-yloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-tert-butyldimethylsilyloxy-3-(tetrahydropyran-2-yloxymethyl)-2-methylene-1-cyclopentanol;

(1R,3R,4S)-4-(biphenyl-4-formyloxy)-3-(biphenyl-4-formyloxymethyl)-2-methylene-1-cyclopentanol;

(4aR,6R,7aS)-2,2-di-tert-butyl-5-methylene-6-hydroxy-6H-hexahydro-cyclopenta[d][1,3,2]dioxasiline;

(2S,4aR,6S,7aS)-2-methyl-5-methylene-6-hydroxy-6H-tetrahydro-cyclopenta[1,3]dioxane;

(2R,4aR,6S,7aS)-2-methyl-5-methylene-6-hydroxy-6H-tetrahydro-cyclopenta[1,3]dioxane; or

(4aR,6S,7aS)-2-methyl-5-methylene-6-hydroxy-6H-tetrahydro-cyclopenta[1,3]dioxane.

20. The method according to claim 1 wherein X is selected from the group consisting of halo, C1-6-alkoxy, halo-C1-C6 alkoxy, or C5-C10-aralkoxy.

21. The method according to claim 1 wherein R and R′ are each independently selected from hydrogen and tert-butoxycarbonyl, provided that R and R′ are not both hydrogen.

22. The method according to claim 1 wherein the reaction of compound 4 with 5 is performed in the presence of Ph3P/EtO2CN═NCO2Et or Ph3P/i-PrO2CN═NCO2-iPr, in a non-protonic solvent selected from the group consisting of aromatic hydrocarbons, halogenated aromatic hydrocarbons, halogenated hydrocarbons or ethers.

23. The method according to claim 1 wherein deprotection of compound 6 is effected in presence of a reagent selected from the group consisting of hydrochloric acid or hydrogen fluoride, formic acid tetra-butylammonium fluoride (TBAF).

24. The method according to claim 1 wherein one step deprotection and hydrolysis of compound 6 is effected by dilute hydrochloric acid in an organic solvent or mixture of organic solvent with water.

25. The method according to claim 1 wherein X is C 1-6 alkoxy, halo-C 1-6 alkoxy or C 5-10 aralkoxy.

26. The compound as claimed in claim 14 wherein R and R′ are each independently selected from the group consisting of C 1-6 alkoxycarbonyl and C 5-10 aralkoxycarbonyl.

27. A compound according to claim 17 wherein R 4 and R 5 , which are the same or different, are independently selected from tert-butyl or phenyl.