Patent ID: RE40040

Claim:
A process for the stereoselective preparation of a compound of formula I wherein: R is a hydrogen atom or a C 1 -C 10 alkyl, C 2 -C 10 alkenyl or C 6 -C 12 arylsulphonyl group, optionally substituted; A, each of which is identical or different, is a hydrogen atom, a nitrogen atom, optionally substituted, a C 1 -C 4 alkyl group, which is optionally substituted by one or more aryl groups, which are, in turn, optionally substituted, an R 2 CO or R 2 SO 2 group, with R 2 being a hydrogen atom, a C 1 -C 8 alkyl group or an aryl group, which are, optionally substituted; and ∇ indicates that the C in the 4″ position has undergone an inversion of configuration with respect to the formula II, from a compound of formula II: wherein: R as defined in formula I and P 1 is a protective group for the hydroxyl functional group at the 2′ position, comprising the steps of: (i) activating the hydroxyl functional group at the 4″ position in the compound of formula II, in order to obtain a compound of formula III: wherein: R and P 1 are as defined in formulae I and II and OR 1 is a leaving group; (ii) contacting the compound of formula III with a nitrogenous nucleophilic derivative under conditions which are sufficient to allow the stereoselective displacement of the hydroxyl functional group activated by the said nitrogenous nucleophile; and (iii) deprotecting the hydroxyl functional group at the 2′ position.