NMR Determination of the Absolute Configuration of an α-Exo-methylene-γ-lactone

Abstract

  Both the enantiomers of the axially chiral reagent, 2′-methoxy-1,1′-binaphthalene-2-carbohydroximoyl chloride (MBCC), were used to convert igalan, an α-exo-methylene-γ-lactone, to yield 4,5-dihydroisoxazoles. The absolute configuration of igalan was determined to be (3aR,5R,6R,7aR)-6-ethenylhexahydro-6-methyl-3-methylene-5-(1-methylethenyl)-2(3H)-benzofuranone (IUPAC name) on the basis of NOE correlations in these derivatives. The absolute configurations of other α-exo-methylene-γ-lactones can be determined by the same method.