Asymmetric R and S warfarin and its analogs

Abstract

The present invention provides a novel process for making compounds of formula 2a or 2b or pharmaceutically acceptable salts thereof, ##STR1## wherein R.sub.1 is selected from the group consisting of phenyl and phenyl substituted with at least one group selected from NO.sub.2 and halogen; R.sub.2 is H; R.sub.3 is selected from the group consisting of C.sub.1-4 alkyl, phenyl, and benzyl; and, R.sub.4 is selected from the group consisting of H and halogen; which comprises the steps of: a) oxidizing a racemate of formula 2 or a salt thereof to form a dehydro-compound of formula 3, ##STR2## wherein R.sub.5 is selected from the group consisting of H, CH.sub.3, benzyl, C.sub.2-8 acyl Na, Li and K; and, b) asymmetrically hydrogenating a compound of formula 3 in the presence of a chiral phosphine catalyst to form a compound of formula 2a or 2b.

Dependencies are inferred from the claim text.