In step (e), the compound of formula VII is chirally reduced by reaction in an anhydrous organic solvent such as CH2 Cl2, THF or toluene, in the presence of a borane, such as BH3 ???(CH3)2 S or borane-THF complex, and a chiral reduction catalyst such as ##STR22## at a temperature in the range of about -30 to about 0??? C., with a range of about -20??? to about -10??? C. being preferred.