摘要：

Describes a highly efficient route to N-tert-butoxycarbonyl-(N-Boc) protected beta-amino acids via the enantionselective addition of silyl ketene acetals to N-Boc-aldimines catalyzed by thiourea catalysts. Emergence of urea derivatives as useful catalysts for the asymmetric hydrocyanation of N-allyl or N-benzyl aldimines and ketoimines.

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