Practical synthesis of (+)-alloisoleucine

Subsequent treatment of N-crotoyl-(1S,2R)-bornane-10,2-sultam with EtMgCl, recrystallization of the product and saponification, afforded R-(-)-3-methy lpenthanoic acid which was used for acylation of (1R,2S)-bomane-10,2-sultam . The product was converted into N-[(2S,3R)-2-amino-3 -methylpentanoyl]-(1R ,2S)-bornane-10,2-sultam by hydroxyamination with 1-chloro-1-nitrosocyclohe xane, followed by reduction of the hydroxylamine grouping. Saponification o f the sultam imide provided (+)-alloisoleucine.