Synthetic studies in the alkaloid field-VII1 1 VI: M. Lounasmaa and M. Puhakka, Acta. Chem. Scand. B32, 77 (1978). Stereochemistry of 1,2,3,4,6,7,12,12b-octahydroindolo [2,3-a]quinolizine derivatives prepared by alkaline decarboalkoxylative cyclization or acid-induced cyclization of appropriate tetrahydropyridines

Article abstract of DOI:10.1016/0040-4020(78)80219-1

The C(12b)-C(1)-C(2) stereochemical relationship in several racemic 1,2,3,4,6,7,12,12b-octahydroindolo [2,3-a]quinolizine derivatives has been determined by ¹³C NMR spectral analysis. The proper shift assignment was confirmed by recording the spectra of selectively deuterated derivatives. The C(12b)-C(1)-C(2) stereochemical relationship in indolo[2,3-a]quinolizines obtained either by alkaline decarboalkoxylative cyclization or by acid-induced cyclization of partially hydrogenated 1-[2-(3-indolyl)ethyl]-3-methoxycarbonylpyridine derivatives is discussed. The ambiguity existing in the preparation of dl-18,19-dihydroantirhine 2 by analogous decarboalkoxylative cyclization is considered.