Structures of tabernaelegantines A–D and tabernaelegantinines A and B, new indole alkaloids from Tabernaemontana elegans

Abstract

The structures of tabernaelegantines A–D [(1)–(4)] and tabernaelegantinies A and B [(5)–(6)], new ‘dimeric’ indole alkaloids isolated from the root bark of Tabernaemontana elegans Stapf., have been determined from their i.r., u.v., mass, and ¹H and ¹³C n.m.r. spectra. The structural elucidation required the analysis of the carbon-13 spectra of voacangine, dregaminol, and tabernaemontanol. The ¹³C n.m.r. investigation supports the revision of the reported configurations at C-20 of dregamine and tabernaemontanine.