α-Hydroxymethylaspartic acid: Synthesis and absolute configuration by X-ray analysis of its derivative (+)-4-benzoylamino-4-carboxy-γ-butyrolactone

Abstract

(+)-4-Benzoylamino-4-carboxy-γ-butyrolactone was synthesized, and its structure solved by direct methods and refined toR=0.033. The molecule adopts a skew conformation with a C7-N1-C8-C12 torsion angle of 59.6(2)°. The lactone ring has an envelope conformation, with the C^α(8) atom deflected from the ring plane. The absolute configuration of (+)-benzylami-no-4-carboxy-γ-butyrolactone5 was assigned asR by the application of Hamilton's test to the unique diffraction data, and confirmed by the estimation of the Bijvoet coefficientB fromhkl and$\overline {hkl}$ diffraction data. This result proves theR configuration for (+) enantiomer of the parentα-hydroxymethylaspartic acid.