AMARYLLIDACEAE INTERCONVERSIONS . PARTIAL SYNTHESES OF [2]BENZOPYRANO[3,4-C]INDOLES

Partial syntheses of pretazettine (7a), precriwelline (7b), and several related compounds are reported. Evidence is cited that haemanthidine (1a), 6-hydroxycrinamine (1b), and many derivatives of these alkaloids undergo a reversible rearrangement to the [2]benzopyrano[3,4-c]indole nucleus under mild conditions. Variations in temperature, solvent, or pH are often sufficient to alter the basic ring system. Biosynthetic implications of these transformations are outlined. Evidence for the α configuration of the C6a,-hydroxyl group of tazettine is presented. © 1969, American Chemical Society. All rights reserved.