SYNTHESIS OF DIPEPTIDES CONTAINING NOVEL CYCLOPROPYL-SUBSTITUTED AND CYCLOPROPENYL-SUBSTITUTED BETA-AMINO AND GAMMA-AMINO ACIDS

The N-silylated methyl 2-aminocyclopropanecarboxylate 1 can be incorpo rated into a dipeptide via a CsF-mediated condensation reaction with N -tosylated phenylalanine chloride 5. Due to its instability the corres ponding free beta-amino acid 4 could not be isolated up to now, and pe ptides containing this structural element have previously not been acc essible. After desilylation, the aminomethyl-substituted cyclopropane or cyclopropene derivatives trans-10, 12, and 13 also provided N-prote cted dipeptides in good yields.