A Singlet Oxygen Mediated New Access to Hydroxyindolenine-Catharanthine Derivatives by Two Sequential Oxidations
摘要:
Formation of hydroxyindolenine derivatives by photoinduced oxidation by singlet oxygen of intermediate 3 beta -cyanocatharanthine (3) allows us to synthesize under mild conditions new alkaloids derivatives, 3 beta -cyano-7 beta -hydroxyindolenine-catharanthine (5), 3 beta -cyano-7 beta -hydroxyindolinecatharanthine (6) and 7 beta -hydroxy-indolenine-catharanthine (7), bearing protected indole moities.
A Singlet Oxygen Mediated New Access to Hydroxyindolenine-Catharanthine Derivatives by Two Sequential Oxidations
摘要:
Formation of hydroxyindolenine derivatives by photoinduced oxidation by singlet oxygen of intermediate 3 beta -cyanocatharanthine (3) allows us to synthesize under mild conditions new alkaloids derivatives, 3 beta -cyano-7 beta -hydroxyindolenine-catharanthine (5), 3 beta -cyano-7 beta -hydroxyindolinecatharanthine (6) and 7 beta -hydroxy-indolenine-catharanthine (7), bearing protected indole moities.
The irradiation, by visible light, of (+)-catharanthine 1 and of (−)-16-O-acetylvindoline 5 in the presence of cyanide ion and a catalytic amount of a photosensitizer known to produce singlet oxygen leads to (+)-3β-cyanocatharanthine 3 and the new (−)-16-O-acetyl-3α-cyanovindoline 6. The complete stereostructural identification of these compounds has been ascertained by an accurate spectroscopic survey. High regio- and diastereoselectivities (de > 99%) are observed. Some experiments have been performed which confirm unambiguously that singlet oxygen is the oxidizing species in such photochemical conditions.
A clean and efficient access to the cleavamine skeleton is described through the selective oxidative C-16-C-21 bond cleavage of catharanthine. The best result is obtained by the use of catalytic quantities of beta -lapachone as photosensitizer. which permits the successful control of competition between the back electron transfer. the deprotonation and the fragmentation pathway. (C) 2001 Elsevier Science Ltd. All rights reserved.
A Singlet Oxygen Mediated New Access to Hydroxyindolenine-Catharanthine Derivatives by Two Sequential Oxidations
作者:Clotilde Ferroud、Patrice Rool
DOI:10.3987/com-00-9138
日期:——
Formation of hydroxyindolenine derivatives by photoinduced oxidation by singlet oxygen of intermediate 3 beta -cyanocatharanthine (3) allows us to synthesize under mild conditions new alkaloids derivatives, 3 beta -cyano-7 beta -hydroxyindolenine-catharanthine (5), 3 beta -cyano-7 beta -hydroxyindolinecatharanthine (6) and 7 beta -hydroxy-indolenine-catharanthine (7), bearing protected indole moities.