Alkaloids yohimbe

Corynanthe yohimbe (Pausinystalia yohimbe Rubiaceae) is a evergreen tree native to the southern part of Africa and to Cameroon, Nigeria, and Zaire. Occasionally it is planted in tropical countries. Its bark coontains a total of 0.3%-1.5% alkaloids. The well known indole alkaloid yohimbine has been obtained as a major alkaloid from the bark. The bark has been used traditionally as an aphrodisiac by African natives. Yohimbine hydrochloride is used as an adrenergic blocker for humans. 

Corynantheine and several yohimbine congeners, such as corynanthine, allo-yohimbine, a-yohimbine, pseudoyohimbine, and )ff-yohimbine, have been also isolated as minor alkaloids from the bark. 

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The remaining yohimb alkaloids are described below ten of them are isomerides of yohimbine, and for convenience of comparison are dealt with in the table on p. 502. 

Constitution of Yohimbine and its Isomerides. The yohimb alkaloids are methyl esters of acids. Yohimbine, yohimbene, mesoyohimbine (isoyohimbine) and y-yohimbine (table, p. 502) are hydrolysed to four, distinct, monocarboxylic acids, C2,yH2402N2, each of which on decarboxylation by heating with soda-lime yields yohimbol, long supposed to be a secondary alcohol, Ci,yH240N2, but which Witkop has shown to be a ketone and has re-named yohimbone, C18H22ON2, m.p. 307° (dec.),... 

A variety of l,2,3,4-tetrahydro-j8-carbolines have been prepared from 3-piperidone phenylhydrazone derivatives. Used initially to obtain pentacyclic derivatives (35) related to the yohimbe alkaloids, this route was later extended to the synthesis of tetracyclic compounds (36). l-Methyl-5,6,7,8-tetrahydro-j8-carboline (37) was prepared in low yield by heating cyclohexanone 2-methyl-3-pyridylhydrazone with zinc chloride, a synthesis probably based on the similar preparation of the tetracyclic compound 38 starting from the corresponding quinolylhydrazine. Abramovitch and Adams extended this approach to the cyclization of cyclohexanone 3-pyri-dylhydrazone (39) itself. The main product was 6,7,8,9-tetrahydro-8-carboline (40), a smaller amount of the j8-isomer (41) also being obtained. This provides a convenient and readily reproducible route to the otherwise difficultly accessible 8-carboline ring system. The favored attack at carbon-2 over carbon-4 of the pyridine nucleus... 

The Yohimbe alkaloids such as alloyohimbane (1) and the antihypertensive drug reserpine constitute attractive goals for synthetic chemists. Syntheses of Yohimbe alkaloids from noncarbohydrates have been reported. " Synthesis of 1 from cellulose has also been achieved (Scheme 1). Pyrolysis of cellulose gave the levoglucosenone (l,6-anhydro-3,4-dideoxy- 3-D-glycero-hex-3-enopyrano-2-ulose, 2), which underwent Diels-Alder cycloaddition with... 

Quaternary derivatives of the yohimbe alkaloids have recently been shown to exhibit paralyzing activity (48, 111). The best of the series, iV-methylhexahydrotetrabyrinium chloride, is effective in a dose of 3.4 mg./kg. in the rabbit head-drop assay and it has a very low toxicity. 

Yohimbine, which is described in Sect. 5.2.2.6.S on Yohimbe alkaloids, has also been isolated from the roots of Rauwolfia serpentina (67). 

Huebner CF, Lucas R, McPhullamy HB, Ttoxell HA (1955) Rauwollia alkaloids. XIV. Derivatives of Yohimbe Alkaloids. J Am Chem Soc 77(2) 469-472... 

Ylangocamphor, T28 Yohimbane, KIO Yohimbe alkaloids, K9-10 Yohimbine, K9 epz-a-yohimbine, K9 16-yohimbone, K9... 

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