CHELATED 2-FORMYLGLYCINATE - ALDEHYDE OR ENOL

C-13 n.m.r. data are presented which are consistent with the proposal that 2-formylglycinate chelated to bis(ethane-1,2-diamine)cobalt(III) exists as an equilibrium mixture of its hydrate, 3,3-dihydroxyalaninat e (c. 90%), and its E-enol, (E)-2-amino-3-hydroxyacrylate (c. 10%). Th e new structural assignment for the minor component of the mixture lea ds to the proposal of a new mechanism for the formation of coordinated penicilloates by reaction of this mixture with (S)-penicillamine. The new mechanism makes it possible to rationalize the remarkable stereos electivity of this condensation reaction.