A convergent, large-scale, chiral synthesis of isoxazoline 1 has been achieved in 37% overall yield and> 99.6% optical purity, starting from l-asparagine and 4- cyanobenzaldehyde. Hofmann reaction of N α-n-Boc-l-asparagine with iodosobenzene diacetate provides optically pure N α-n-Boc-l-α, β-diaminopropionic acid (8) in 75% yield. A process of lipase resolution-base catalyzed epimerization gives the single enantiomer 5. ...
