Use of an acetylenic sulfone as an alkene dipole equivalent in the synthesis of (±)-pumiliotoxin C

The cycloaddition of methyl cis-2-amino-trans-6-methylcyclohexanecarboxylate (3) with 1-p-(toluenesulfonyl)-1-pentyne (4) afforded the corresponding enaminone 2, that was in turn reduced to (+/-)-pumiliotoxin C (1). The acetylenic sulfone 4 thus functions as the synthetic equivalent of the alkene dipole 5 in this process. (C) 1997, Elsevier Science Ltd.