Homologation of <i>α</i>-amino acids to <i>β</i>-amino acids: 9-Fluorenylmethyl chloroformate as a carboxyl group activating agent for the synthesis of <i>N^α-</i> protected aminoacyldiazomethanes

Abstract

2152-2158An efficient and stereospecific homologation of urethane-protected α-amino acids to β-amino acids by Arndt-Eistert approach using an equimolar mixture of Fmoc-/Boc-/Z-α-amino acid and 9-fluorenylmethyl chloroformate for the acylation of diazomethane synthesizing the key intermediates Fmoc-/Boc-/Z-α-aminoacyldiazo-methanes as crystalline solids is described. They are then converted to the corresponding,β-amino acids using silver benzoate/1,4-dioxane-water under microwave irradiation. All the protected β-amino acids prepared have been obtained in good yield as well as purity