XY–ZH systems as potential 1,3-dipoles. Part 10. The decarboxylative route to azomethine ylides. Background and relevance to pyridoxal decarboxylases

Abstract

The reaction of primary and α,α-disubstituted α-amino acids with pyridoxal in the presence of N-phenylmaleimide in various solvents at temperatures up to 120 °C gives rise to two series of cycloadducts. One series arises from azomethine ylides formed by decarboxylation of the intermediate pyridoxal imines whilst the other series arises via azomethine ylides derived by 1,2-prototropy in the same pyridoxal imines. The relevance of the decarboxylative route to azomethine ylides to the Strecker degradation and to pyridoxal-mediated decarboxylase enzymes is discussed.