Pursuit of optimal carbohydrate-based anticancer vaccines: preparation of a multiantigenic unimolecular glycopeptide containing the Tn, MBr1, and Lewis(y) antigens

A novel preparation of nonnatural glycoamino acids starting from n-pentenyl glycosides is described. The approach involves a Horner-Emmons olefination with a suitably protected glycine-derived phosphonate, followed by catalytic asymmetric hydrogenation, which proceeds with excellent diastereomeric selectivity. The synthetic methodology was useful for the preparation of glycoamino acids containing the Tn antigen, the MBr1 antigen (Globo-H), the Le(y) antigen, and lactose. These glycoamino acids can also serve as units for peptide synthesis. The synthesis of polyvalent glycopeptides containing three different antitumor antigens is described (28 and 29), and these have been prepared for conjugation to carrier protein in order to access the immunogenicity for tumor immunotherapy applications.

Optical resolution and absolute configuration of N-benzyloxycarbonyl-alpha-alkoxyglycines

Optical resolution of racemic N-benzyloxycarbonyl-protected alpha-alkoxyglycines, (+/-)-Cbz-Gly(OR)-OH (R = Et and Pr(i)), was achieved by means of fractional crystallization of diastereomeric salts with (+)-(1S,2S)-2-amino-1-phenyl-1,3-propanediol or diastereomeric esters of (+)- or (-)-menthol. The D- and L-configurations were assigned to the (+)- and (-)-Cbz-Gly(OR)-OH, respectively, based on L-enantioselective enzymatic hydrolysis of (+/-)-Cbz-Gly(OR)-OR' (R = Me, Et, and Pr(i); R' = CH(2)CF(3) and Me) using porcine pancreatic lipase and papain. Chiroptical properties and HPLC retention times of D- and L-Gly(OR)-residue (R = Me and Pr(i))-containing peptides were compared in relation to their configurational assignments. Copyright 1999 Wiley-Liss, Inc.