Isolation and synthesis of an alpha-malamic acid derivative from Justicia ghiesbreghtiana.

A polar extract of leaves of Justicia ghiesbreghtiana yielded N-(2-hydroxy-4,5-dimethoxyphenyl)-(S)-alpha-malamic acid, 1. Incomplete spectral analysis yielded a hypothetical structure, which was then proven by total synthesis. Coupling of the trifluoroacetate of malic anhydride (trifluoroacetoxysuccinic anhydride) with an arylamine provided the key to regiospecific preparation of the alpha- rather than beta-malamic acids.