Synthesis of all low-energy stereoisomers of the tris(pyrrolidinoindoline) alkaloid hodgkinsine and preliminary assessment of their antinociceptive activity

The previously unknown stereoisomers 3, 4, ent-1, and ent-4 of the tris(pyrrolidinoindoline) alkaloids hodgkinsine (1) and hodgkinsine B (2) were prepared by stereocontrolled total synthesis. In each synthesis, a catalyst-controlled intramolecular Heck reaction was the key step in appending a third cis-pyrrolidinoindoline ring to a hexacyclic chimonanthine precursor. Results of the preliminary evaluation of these hodgkinsine stereoisomers in the tail flick and capsaicin pain models are reported.