Amaryllidaceae alkaloids: (+)-tazettine, (+)-3-O-demethylcriwelline and (+)-3-epimacronine at 173 K

The Amaryllidaceae alkaloids (+)-tazettine [(+)-(3S,4aS,6aS:1 3bS)-3-methox y-5-methyl-3,3,4a,5,6,6a-hexahydro- 8H,11H-[1,3]dioxolo[6,7] [2]benzopyrano [3,4-c]indol6a-ol, C18H21NO5] and partially hydrated (+)-3-epimacronine [()-(3S,4aS,6aR,13bS)-3-methoxy-5-methyl-3,4,4a,5,6,6a-hexahydro-8H,11H-[1,3] dioxolo[6,7][2]- benzopyrano[3,4-c]indol-8-one 0.066-hydrate, C18H19-NO5.0. 066H(2)O] have been extracted from Galanthus plicatus subsp. byzantinus, wh ile (+)-3-O-demethyl-criwelline [(+)-(3R,4aS,6aS,13bS)-5-methyl-3,4,4a,5,6, 6a- hexahydro-8H,11H-[1,3]dioxolo[6,7][2]benzopyrano[3,4c]indole-3,6a-diol, C17H19NO5] has been isolated from the plant Galanthus gracilis. These comp ounds have the ring skeleton of the tazettine or [2]benzopyrano[3,4-c]indol e subgroup. (+)-3-O-Demethylcriwelline is a new alkaloid and is the 3-O-dem ethyl C3-epimer of (+)-tazettine. The geometrical features of the compounds differ predominantly in the conformations of the pyrrolidine and pyran rin gs.