Total Synthesis of (−)-Macrocarpal C. Stereoselective Coupling Reaction with a Novel Hexasubstituted Benzene Cr(CO)3 Complex as a Biomimetic Chiral Benzyl Cation Equivalent

Abstract

The first total synthesis of (−)-macrocarpal C (3) is described. The synthesis features a highly stereoselective coupling reaction of silyldienol ether 6 with biomimetic benzyl cation species (R)- and (S)-B, which were generated from novel hexasubstituted benzene chromium tricarbonyl complexes (R)- and (S)-17. At the final step of the total synthesis, we developed the tris-O-demethylation of macrocarpal C trimethyl ether 34 under basic conditions using lithium p-thiocresolate. Moreover, spectroscopic evidence shows that the synthetic (−)-3 is identical to natural macrocarpal G (4).