| abstract |
Optically active alpha -bromo- or alpha -chlorocarboxylic compounds of the formula <IMAGE> I wherein X is bromine or chlorine; M is hydrogen, NR4+1 or a cation of an alkali or alkaline earth metal; R1 is hydrogen or lower alkyl; n is 0 or 1; R is hydrogen, C1-C20 alkyl, or C1-C20 alkyl substituted in the terminal position with -NR22, -COOR2, -OR3, a free or protected -CHO group or a ring A; R2 is hydrogen or a lower alkyl; R3 is hydrogen or a protecting group; ring A is an unsubstituted or substituted ring; and * is a center of chirality, are prepared by enantioselectively hydrogenating, in the presence of a ruthenium complex of an optically active diphosphine ligand, a (Z)- alpha , beta -unsaturated compound of the general formula <IMAGE> II wherein R, n, X and M are as defined above. |