Total Syntheses of (±)-Crinine, (±)-Crinamine, and (±)-6a-epi-Crinamine via the Regioselective Synthesis and Diels−Alder Reaction of 3-Aryl-5-bromo-2-pyrone

We have devised a new unified synthetic protocol to (±)-crinine, (±)-crinamine, and (±)-6a-epi-crinamine from the Diels−Alder cycloadduct of 3-(3,4-methylenedioxyphenyl)-5-bromo-2-pyrone with TBS vinyl ether. The requisite 3-(3,4-methylenedioxyphenyl)-5-bromo-2-pyrone was prepared from the C3-selective Stille coupling reaction of 3,5-dibromo-2-pyrone. Also noted is that the vinyl bromide can be used as a handle for further derivatization.