Preparation, isolation and X-ray crystallographic structure determination of a stable, crystalline carbonic anhydride of an N-protected α-amino acid

Abstract

The reaction of methyl (2S,3aR,8aS)-2-carboxy-8-phenylsulfonyl-1,2,3,3a,8,8a-hexahydropyrrolo-[2,3-b] indole-1 -carboxylate and isobutyl chloroformate in tetrahydrofuran at –15 °C in the presence of trimethylamine results in the formation of the corresponding mixed carboxylic–carbonic anhydride. This unusually stable mixed anhydride was isolated in the form of an analytically pure crystalline solid and its structure verified crystallographically.