- SYNTHESIS OF STEREOISOMERIC VINCAMINES
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The synthesis of (+/-)-vincamine (I), (+/-)-16-epi-vincamine (XVIII) and (+/-)-16-epi-21-epivincamine (XVII) from 1-ethyl-2,3,4,6,7,12-hexahydroindoloquinolizine (IV) and 2-chloroacrylonitrile is described.It is characterized by a novel method of oxidation of the key intermediates, (+/-)-deoxyvincamine (II) and (+/-)-16-epi-21-epi-deoxyvincamine (XIII) with oxodiperoxymolybdenum (pyridine) (hexamethylphosphoric triamide).The deoxy derivatives II and XIII were prepared by direct or stepwise acid or alkaline hydrolysis od stereoisomeric (+/-)-eburnane-16-carbonitriles IX-XII, obtained by reduction of the primary immonium salt V, and subsequent esterification.In some cases, the hydrolysis is accompanied by epimerization at C(16).
- Koblicova, Zdena,Holubek, Jiri,Trojanek, Jan
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p. 2722 - 2730
(2007/10/02)
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- A NEW APPROACH TO (+/-)-APOVINCAMINE
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A new approach to (+/-)-apovincamine, 2, is reported which bypasses the formation of (+/-)-vincamine, 1, and includes the dehydration of the β-hydroxy ester 7, obtained by regio-controlled alkylation of the stereochemically suitable aldehyde 6 with methyl chloroacetate.Using ethyl chloroacetate, the clinically useful apovincamine analogue, (+/-)-Cavinton, 3, is obtained. (+/-)-Apovincamine is then converted to (+/-)-vincamine, 1, by base-catalyzed oxygenation of the mixture of (+/-)-dihydroapovincamines 8 and 9.
- Danieli, Bruno,Lesma, Giordano,Palmisano, Giovanni
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p. 257 - 268
(2007/10/02)
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