Total Synthesis of (−)-Incarvilline, (+)-Incarvine C, and (−)-Incarvillateine

The first total syntheses of new monoterpene alkaloids (−)-incarvilline, (+)-incarvine C, and (−)-incarvillateine, corresponding to the natural enantiomers, have been accomplished. The strategy for the synthesis of these natural products utilized 6-epi-incarvilline as a common precursor, which was assembled by a three-component coupling reaction using (4S)-4-siloxy-2-cyclopenten-1-one to construct an appropriately trisubstituted cyclopentanone, followed by ring closure to the cis-perhydro-2-pyrindine skeleton by means of a reductive Heck-type reaction. Furthermore, topochemically controlled [2 + 2] photodimerization of cinnamic acid derivatives in the solid state for the stereospecific construction of a 1,2,3,4-tetrasubstituted cyclobutane ring was also investigated as a means to access (−)-incarvillateine.