Synthesis of (-)-Hobartine and Related Indole Alkaloids

Article abstract of DOI:10.1002/hlca.19840670417

An improved method for obtaining optically pure (S)-(1-p-menthen-8-yl)amine (12) has led to expedient syntheses of two hypothetical biogenetic intermediates on the way (S)-N-(1-p-menthen-8-yl)-2-(3-indolyl)ethylideneamine (4).The latter has been transformed into (-)-hobartine (6) in 64percent yield via stereoselective biomimetic cyclization by treatment with HCOOH.This unambiguous synthesis establishes the hitherto unknown absolute configuration of (-)-hobartine (6).Several model cyclization reactions of N-substituted α-(terpen-8-yl)imine derivatives yielding unsaturated 3-azabicyclo<3.3.1>nonane compounds are described.