Tirucallanes

McChesney JD, Dou J, Slndelar RD, Goins DK, Walker LA, Rogers RD (1997) Tirucallane-type Trlterpenolds NMR and X-ray Diffraction Analyses of 24-Epi-piscidinol A and Plscldlnol A. J Chem Crystallogr 27 283... 

New tirucallane triterpenoids are adenophorate (70) (T-ray analysis) from Adenophora triphylla (Campanulaceae),32 and the ring a seco derivatives (71) and (72) from Guarea cedrata (Meliaceae).52 Treatment of the 7a-hydroxy- or 7-keto-apotirucall-14-enes (73)—(75) with monoperphthalic acid affords the corresponding 14a,15a-epoxides.53... 

Sapelin A (69) and sapelin B (70) have been obtained" from Entandrophragma cylindricum (Meliaceae) and are further examples of the group of euphane or tirucallane derivatives which co-occur with, and are likely precursors of, tetranor-triterpenoids (see later). Sapelin A was readily correlated with bourjotinolone A (71 ). Sapelin B reacted with sodium periodate to give the dialdehyde (72) which was transformed successively by sodium amalgam and chromium trioxide into the y-lactone (73) previously obtained from sapelin A and bourjotinolone A. 

Tirucallanes and die 20-epimerie euphanes are frequently found in Euphorbiaeeae, and are exemphed by tirucallol and its (20/ )-epimer euphol from Euphorbia tiru-calli and related speeies. 

Tirucalla-7,24-dien-3p-ol, a regioisomer of tirucallols, is found among the constituents of the seed of black tea Camellia sinensis, Theaceae). Euphorbol isolated from various Euphorbiaceae represents a homotriterpene with a tirucallane skeleton. 

Itokawa H, Kishi E, Morita H, Takeya K (1992) Cytotoxic quassinoids and tirucallane-type triterpenes from the woods of Eurycoma longifolia. Chem Pharm Bull 40 1053-1055... 

It should be noted that a number of tetranortriterpenoids have been isolated from Cneoraceae. Protolimonoids (zl -tirucallanes with highly oxygenated side-chain - e.g., 511) have been encountered in all four families, as anticipated on the basis of biogenetic considerations. 

In addition to the known boswellic acids mentioned above, more than 15 triterpene acids have recently been isolated from olibanum resin. They belong to the lupane (e.g., lupeolic acid), ursane (e.g., 11-keto-P-boswellic acid), oleanane (e.g., 3-a-acetyl-11-keto-a-bosweUic acid), and tirucallane (e.g., 3-0X0- and 3-hydroxy-tirucallic acids) classes of triterpenes. ... 

The euphane and tirucallane triterpenes differ from the lanostanes only in having the opposite stereochemical dispositions at C13, C14, and Ci7 and are themselves epimeric at C20 384). The stereochemistry is considered to be a consequence of enzymatic cyclization of squalene epoxide (305) from a chair, chair, chair conformation (Scheme 29). The two stereoisomeric forms arise from 17->20 hydrogen shift to the dia-stereotopic faces of the carbonium ion at C20. ... 

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