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Catharanthine epoxides

Most of the transformations carried out on catharanthine have naturally been concerned with the preparation of potential precursors of dimeric bases related to vinblastine. For example, 15-acetoxydihydrocatharanthine (configuration at C-15 unknown) is also obtained, together with the recently reported221 20-acetoxydi-hydrocatharanthine, when catharanthine is subjected to the modified Prevost reaction.139 The conversion of catharanthine (236) into the potentially useful epoxides (237a), (237b), and (239), the lactone (238), and the diol (240) (stereochemistry at C-15 and C-20 not rigorously proved) has also been described (Scheme 25).140,141... [Pg.201]

The same sequence of reactions has also been accomplished by Kutney et a/.,162 from the j3-epoxide (239) the process is described as efficient, but the yield of leurosine obtained is unspecified. In the course of this synthesis, an improved preparation of the epoxide (239) from catharanthine (236) via the lactam epoxide (265) was developed (Scheme 26).162... [Pg.210]

Enantiomerically pure epoxide 307 was synthesized in 16 steps from D-(-)-quinic acid, an inexpensive plant metabolite. Intramolecular cyclization was observed with a catalytic amount of tetrakis(triphenylphosphine)palladium(0) at 25 °C to afford the optically active isoquinuclidine in 95% yield. The introduction of alkyl groups, such as the ethyl group of ibogamine and catharanthine, can easily be accompUshed at the epoxy ketone stage. [Pg.460]


See other pages where Catharanthine epoxides is mentioned: [Pg.98]    [Pg.104]    [Pg.209]    [Pg.429]    [Pg.264]    [Pg.16]   
See also in sourсe #XX -- [ Pg.97 ]




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