Synthesis of 2-fluoro analogues of frontalin

The synthesis of enantiomerically and diastereomerically pure (-)- (1R,2R,5R)- and (-)-(1R,2S,5R)-2-fluoro frontalin (7) starting from (+)-(1S)- menthyl-(R)-toluene-4-sulfinate, methylmagnesium bromide, methyl fluoroacetate, 4-pentenyl bromide and diazomethane is described. The absolute stereochemistry was unambiguously determined by X-ray analysis of (+)- (1S,2R,5S,Rs)-5, an intermediate in the synthesis of the enantiomeric (+)- (1S,2R,5S)-2-fluoro frontalin (7).