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-methylpenthanoic acid which was used for acylation of (1R,2S)-bornane-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-nitrosocyclohexane, followed by reduction of the hydroxylamine grouping. Saponification of the sultam imide provided (+)-alloisoleucine.     

An Entry to the Optically Pure β-Lactam Skeleton Based on 1,3-Dipolar Cycloaddition of Nitrones to 4,6-Di-O-Acetyl-2,3-Dideoxy-D-Threo-Hex-2-Enono-1,5-Lactone

Abstract

Saturated lactone 8, easily available by 1,3-dipolar cycloaddition of nitrone 4 to unsaturated lactone 7 was transformed into the β-lactam 22having a polyol side chain at the C-3 position of the azetidinone ring. The same sequence of reactions, when applied to 9 and 10 failed to give the respective β-lactams owing to the removal of the nitrogen atoms from those molecules.     

1,3-dipolar cycloaddition of nitrones to sugar enlactones

It was found that 1,3-dipolar cycloaddition of nitrones derived from formaldehyde and acetaldehyde to sugar enlactones proceeds regio- and stereospecifically to afford anti - endo adducts.