A formal synthesis of (+)-madindoline A was achieved. The Sunazuka's key intermediate, (4R,5S)-(-)-3-butyl-4-(tert-butyldimethylsiloxy)-5- methoxycarbonyl-2,5-dimethyl-2-cyclopentenone, was synthesized from easily available (2S,3S)-3-acetoxy-2-ethenyl-2-methylcyclopentanone. The starting material was reliably supplied by a chemo-enzymatic procedure in enantiomerically pure form. The synthesis was performed by straightforward transformations involving enone formation and regioselective introduction of the two alkyl side chains.
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