Patent ID: 7439351

Claim:
A method for the preparation of 2′- or 3′-deoxy- and 2′,3′-dideoxy-β-L-pentofuranonucleoside compounds of formula I: in which B represents purine or pyrimidine base selected from the group consisting of adeninyl, guaninyl, hypoxanthinyl, uracilyl, thyminyl, cytosinyl, 5-halo-uracilyl and 5-halo-cytosinyl; R 1 represents OH; R 2 and R 3 represent, independently of each other, H or OH; and at least one of R 2 and R 3 represents H; comprising the following steps: 1) a compound of formula (II) is condensed with the base B′ with an appropriate coupling reagent in order to obtain the compound of formula (III) according to the scheme wherein: R′ 1 and R′ 2 have the meanings given for R 1 and R 2 except that when R 1 and R 2 represent OH, the OH group is protected by a protecting group selected from the group consisting of an acyl, a benzoyl, a benzyl and a silyl group, R′ 3 is a C 1 to C 5 alkyl group or a phenyl radical, X is a leaving group selected from Cl, Br, I, a C 1 to C 5 acyloxy and C 1 to C 5 alkoxy group, B′ is a purine or pyrimidine base B which is protected by an amino protecting group selected from the group consisting of an acyl, a benzoyl, a benzyl and a silyl group when necessary, 2) the R′ 3 COO group at the 2′ position is removed by deacetylation so as to obtain an OH group and a compound of formula 3) optionally, the OH group at the 2′ position is removed by a deoxygenation reaction; and 4) where appropriate, the R′ 1 and R′ 2 groups and the B′ base are deprotected so as to obtain the compounds of formula (I).