The application of an allylic strain effect in boron enolates and asym
metric Michael-like addition/electrophilic bromination reactions is re
ported for the asymmetric synthesis of the individual isomers of unusu
al constrained amino acids. For beta-substituted alpha-amino acids, al
l of the final optically pure products were identical to authentic sam
ples, which provided further and unequivocal evidence to confirm the a
ssignments of stereochemical control of the new methods in this report
.