<i>trans</i>-Cyclopropyl β-Amino Acid Derivatives via Asymmetric Cyclopropanation Using a (Salen)Ru(II) Catalyst

trans-Cyclopropyl β-amino acid derivatives can be synthesized in five steps with excellent enantioselectivities using a chiral (Salen)Ru(II) cyclopropanation catalyst in the key asymmetry-induction step. This facile synthesis proceeds with high overall yield and can be used to prepare a number of carbamate-protected (Cbz and Boc are demonstrated) β-amino acid derivatives.