Enantioselective Alkylation of Amino Acid Derivatives Promoted by Cyclic Peptoids under Phase-Transfer Conditions

The effects of substituents and cavity size on catalytic efficiency of proline-rich cyclopeptoids under phase-transfer conditions were studied. High affinity constants (K a) for the sodium and potassium cations, comparable to those reported for crown ethers, were observed for an alternated N-benzylglycine/l-proline hexameric cyclopeptoid. This compound was found to catalyze the alkylation of N-(diphenylmethylene)­glycine cumyl ester in values of enantioselectivities comparable with those reported for the Cinchona alkaloid ammonium salts derivatives (83–96% ee), and with lower catalyst loading (1–2.5% mol), in the presence of a broad range of benzyl, allyl and alkyl halides.