The intermediates of formula (VI) may be prepared by the reduction of an appropriate lower alkyl ester of formula (V-a-1) with an appropriate reducing agent, such as sodium dihydrobis(2-methoxyethoxy)aluminate, lithium borohydride and the like, or alternatively by eliminating the phenylmethyl group of a compound of formula (XXXII) and thereafter introducing L2 in the usual manner. ##STR43##