ASYMMETRIC OXIDATIVE CYCLIZATION OF O-PHENOLIC OXIME-ESTERS - FIRST SYNTHESIS OF ENANTIOMERICALLY ENRICHED SPIROISOXAZOLINE METHYL-ESTERS

A new method for the synthesis of enantiomerically enriched cyclohexad ienone spiroisoxazoline (-)-2a has been described. Asymmetric intramol ecular oxidative cyclization of the o-phenolic oxime-ester Ic using a novel optically active tertiary alcohol (-)-3 as a chiral auxiliary pr oceeded smoothly to afford cyclohexadienone spiroisoxazoline 2c in 83% yield. Opitcally active tertiary alcohol (-)-3 was synthesizied, from racemic (1S, 8R*, 9R*, 10R*)-8-phenyl-1-decalol (4) by optical resol ution. Removal of the chiral auxiliary in 2c with CF3COOH followed by methylation gave methyl ester (-)-2a in 74% ee (71% chemical yield) ha ving S-configuration. The absolute configuration of 2a was determined by the synthesis of the marine natural product (+)-aerothionin.