An eleven-step reaction sequence starting from enantiomerically pure (−)-muricatacin (6) afforded the key intermediate 12, which was then converted to (15S, 16R, 19S, 20R, 34S)-diepomuricanin (1) via introduction of an acetylene unit and a coupling reaction with iodo lactone synthon 15.
Practical synthesis of a pyrrolidine analog of a mono-THE acetogenin as a proto-type analog to evaluate the effect of a heteroatom in the mono-THF ring of acetogenins was achieved using Pd(II)-catalyzed diastereo-selective cyclization. Ligand-less PdCl2 catalyzed cyclization yielded the desired pyrrolidine derivative as a single major product having the desired relative configurations. Coupling of the pyrrolidine fragment with a known gamma-lactone-containing fragment via a Sonogashira cross-coupling reaction yielded the desired aza-cis-solamin analog.