Studies of enzyme-mediated reactions. Part III. Stereoselective labelling at C-2 of tyramine: stereochemistry of hydroxylation at saturated carbon

Abstract

Synthetic routes to tyramine have been developed which allow stereoselective labelling with isotopic hydrogen at C-2 in configurations established by chemical correlation with [2-²H₁]succinic acid of known absolute configuration. The various labelled tyramines have been converted into samples of O-methylnorbelladine [as (33)] which are used to prove that the hydroxylation step at saturated carbon in haemanthamine biosynthesis occurs (a) stereo-specifically with removal of the pro-R hydrogen atom and (b) with retention of configuration.