Combined C-H activation/cope rearrangement as a strategic reaction in organic synthesis: Total synthesis of (-)-colombiasin A and (-)-elisapterosin B

The total synthesis of (-)-colombiasin A (2) and (-)-elisapterosin B (3) has been achieved. The key step is a C-H functionalization process, the combined C-H activation/Cope rearrangement, between methyl (E)-2-diazo-3-pentenoate and 1-methyl-1,2-dihydronaphthalenes. When the reaction is catalyzed by dirhodium tetrakis((R)-(N-dodecylbenzenesulfonyl)prolinate), Rh-2(R-DOSP)4, an enantiomer differentiation step occurs where one enantiomer of the dihydronaphthalene undergoes the combined C-H activation/Cope rearrangement while the other undergoes cyclopropanation. This sequence controls the three key stereocenters; in the natural products such that the remainder of the synthesis is feasible using standard chemistry.