THERMAL REARRANGEMETS OF SOME INDOLE ALKALOID DERIVATIVES
Under both static and flow thermolysis conditions, several compounds with an "aspidosperma" framework rearranged to "vinca" derivatives.Thus (-)1,2-dehydroaspidospermidine (4) rearranged to (-)aspidospermidine and compound 17 on pyrolysis (200 deg C) while flow termolysis (580 deg C) gave vincane (14).Compound 6 rearranged to vincamine (13a) and 16-epivincamine (13b) under either condition; increasing the temperature resulted in formation of apovincamine (19) (pyrolysis) or vincamone (16) (flow thermolysis).
Hugel, Georgette,Levy, Jean
p. 1067 - 1074
(2007/10/02)
Synthetic Approach to (+/-)- Vincamine via Cleavage of an α-Diketone Monothioacetal. Alternative Synthesis of (+/-)-Eburnamine, (+/-)-Isoeburnamine, and (+/-)-Eburnamenine
The half ester (8) prepared from cleavage of 2-(1,3-dithian-2-yl)-4-ethoxycarbonyl-4-ethylcyclohexanone (7) has been converted into (+/-)-eburnamine (20), (+/-)-isoeburnamine (21), and (+/-)-eburnamenine (22) by a stereospecific reaction sequence proceeding via the dithian intermediate (16).However an attempted conversion of (16) into (+/-)-vincamine (6) was unsuccessful.