Process for the preparation of 7-amino syn 3,5-dihydroxy heptanoic acid derivatives via 6-cyano syn 3,5-dihydroxy hexanoic acid derivatives

A process for the preparation of the intermediate of formula VI

• wherein Ra′ and Rc′ are each independently of the other hydrogen or a hydroxy-protecting group or together are a bridging hydroxy-protecting group, and Rb is a carboxy-protecting group, which is suitable for the preparation of statin derivatives, which process is carried out by conversion of the intermediate of formula XIX
• wherein Ra′ and Rc′ are each independently of the other hydrogen or a hydroxy-protecting group, and Rb is a carboxy-protecting group;
• wherein compound of formula XIX is prepared by a process which comprises the preparation of a compound of formula I
• wherein X is halogen, acyloxy, activated hydrocarbyloxy, activated hydrocarbylthio or —N(CH3)—OCH3, Ra is hydrogen or a hydroxy-protecting group and Rb is a carboxy-protecting group;
• wherein compound of formula I is prepared by conversion a compound of formula XI
• wherein Ra is a hydroxy-protecting group and Rb is a carboxy-protecting group, into the corresponding compound of formula I using a reagent that introduces the radical X.