Patent ID: 7381821

Claim:
A process for preparation of compounds of formula (IV) or pharmaceutically acceptable salts thereof, wherein R 4 represents hydrogen or a group of formula —C(═O)Z 3 ; Z 3 represents a group of formula —OR 1 ′ or —NR 2 ′R 3 ′, in which R 1 ′ represents hydrogen, a hydrocarbon group or an alkali metal, R 2 ′ and R 3 ′, each independently, represent hydrogen or a hydrocarbon group, or —NR 2 ′R 3 ′ represents a heterocycle containing up to 7 ring members, and n is 1, 2, 3, 4, or 5, comprising reacting a compound of formula I: in the form of an (R)-enantiomer, wherein Y is a leaving group and n is 1, 2, 3, 4, or 5, with a compound of formula (V) wherein P 1 represents a hydroxy protecting group and P 2 represents hydrogen or an amine protecting group, with the proviso that P 1 and P 2 are optionally linked to form a single protecting group, and deprotecting the product.