An efficient synthesis of the intrinsic fluorescent peptide labels, (S)- and (R)-(6,7-dimethoxy-4-coumaryl)alanines via asymmetric hydrogenations

The title compounds 1a,b are efficiently synthesized in high yields and with high enantioselectivity (>95% ee) by using a sequence in which the key step involves asymmetric hydrogenation of dehydroamino methyl ester 4 with Burk’s DuPHOS-based Rh(I) catalysts.