Asymmetric Synthesis of Cyclic β-Amino Acids

A convenient synthesis of cyclic β-amino acid derivatives (5-, 6- and 7-rings) is achieved via a four step sequence: (i) stereoselective Michael addition of substituted α-methylbenzylamines to α,β-unsaturated chloroesters; (ii) CAN-mediated deprotection; (iii) cyclisation and (iv) α-chloroethyl chloroformate-mediated α-methylbenzylamine deprotection.