Intramolecular cycloaddition of α-allyloxycarbonylnitrone bearing a chiral sugar auxiliary: A short-step synthesis of the N-terminal amino acid component of nikkomycin Bz

Abstract

Heating 2,3:5,6- O-dicyclohexylidene-L-gulose oxime with methyl glyoxylate hemiacetal followed by treatment of the resulting mixture with allyl alcohols in the presence of catalytic amounts of titanium tetrachloride and molecular sieves 4A caused tandem nitrone formation, transesterification, E, Z-isomerization and diastereofacial selective intramolecular cycloaddition to provide stereocontrolled polycyclic compounds in one step. This method could be applied efficiently to synthesis of the N-terminal amino acid component of nikkomycin Bz.