(e) conducting a chiral catalytic reduction of the compound of formula VII with a borane, such as BH3 ???(CH3)2 S or borane-THF ##STR19## complex, and a chiral catalyst such as ##STR20## to obtain a compound of formula I; (f) optionally, when any of R1, R2 or R3 is a benzyloxy or alkoxy group, converting said benzyloxy or alkoxy group to a hydroxy group, for example conducting a debenzylation reac