Methyl corynantheate

The natural antipode of corynantheine (35, 155, 20/ ) has elegantly been prepared by Autrey and Scullard (168), starting from yohimbone (305), synthesized and resolved previously by Swan (169). Yohimbone (305) was converted to 18-formylyohimbone (306) and then through 307 to oxime 308. On reaction with thionyl chloride, 308 underwent a Beckmann fragmentation to the trans-substituted indolo[2,3-a]quinolizine 310, which after desulfurization and esterification resulted in the levorotatory methyl corynantheate (304). This product... 

Intramolecular ene reactions. Use of Lewis acid catalysts (particularly FeCL, 15,156 16,190-101) has greatly extended the usefulness of intramolecular ene cy-clization. Thus a new diastereoselective route to corynanthe-type alkaloids involves the ene cyclization of 1 to tr s-indolo[2,3-a]-quinolizidine (2), a precursor to methyl corynantheate (3) by demethoxycarbonylation. SnCU (1 equiv.) is the only common Lewis acid that is useful for this particular ene cyclization, and even so, it also requires the presence of trifluoroacetic acid (1.5 equiv.). 

The data given in the table for corynanthine are due to Foumeau and Fiore. Raymond-Hamet later found that corynanthine on alkaline hydrolysis gave a dextrorotatory acid, which Scholz confirmed and identified its methyl ester as yohimbine and suggested that corynanthine is a stereoisomeride of yohimbine. Fourneau and Benoit have confirmed that corynanthine on acid hydrolysis gives 1-corynanthic acid (m.p. 284°, [a]i) — 85-9° pyridine), but on alkaline hydrolysis, even in the cold, some racemisation occurs and the resulting acid is of low lasvo-rotation. They also point out that both yohimbine and corynanthine yield yohimbone on dehydrogenation cf., p. 504) and are probably stereoiso-merides. 

Yohimbine Yohimbine is methyl ether ( )-2a-hydroxyyohimban-la-carboxylic acid (12.2.16). It is isolated from the plants Corynanthe johimbe and Rauwolfia serpentina [60,61], It is also synthesized [62-66],... 

Yohimbine, (16a,I7a) 17-Hydroxyyohimban-I6-carboxylic acid methyl ester quebrachine corynine aphro-dine, C, HuNiOJ mol wt 354.43. C 71.16%, H 7,39%, N 7.90%, O 13.54%. Indole alkaloid with a,-adrenergic blocking activity. Found in Corynanthe johimbe K. Schum., Rubiaceae and related trees, also in Rauwolfla serpentina (L.) Benth., Apocynaceae Raymond -Hamet. J. Pharm. Chim. 

Y. is the main alkaloid of many Aspidosperma species, it also occurs in Rubiaceae such as Corynanthe johimbe i=Pausinystalia) and related trees as well as in some Apocynaceae (e. g., Rauvolfia and Vinca species). Y. is structurally related to the Rauvolfia alkaloids, e. g., reserpine. Y. is the methyl ester of yohimb(in)ic acid (C20H24N2O3, Mr 340.42, mp. 280-300°C). In medicine Y. is used especially in the form of its more water-soluble hydrochloride (decomp. at 302 °C) as a... 

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