Asymmetric cycloadditions of dienes to chloronitroso compounds derived from carbohydrate ketones: Syntheses of (-)-physoperuvine and (+)-epibatidine

An a-chloronitroso compound derived from D-xylose undergoes cycloadditions with cyclic dienes to give bicyclic dihydrooxazines of high enantiomeric purity; such adducts were used in a synthesis of (-)-physoperuvine and a formal synthesis of (+)-epibatidine, whilst a pseudoenantiomeric chloronitroso compound is also available from L-sorbose.