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As part of a phytochemical survey of the family Meliaceae, heartwood timber of the four species of the W7est African genus Entandrophragma has been examined. Light-petroleum extraction of all gave " @ "-sitosterol, and four new and apparently related substances have been isolated. The distribution of these within the genus is described.THE relation of plant chemistry to phylogeny has attracted interest for many years.lY2 The heartwood chemistry of the broad-leaved trees of the division Angiospermae has, except for the genus P t e r o~a " J P z t s ,~~~ been little investigated from this point of view. The family Meliacae contains many species of commercial value, and yields various woods known as " mahogany." The genus Entandrophragma, limited to four West African ~pecies,~ is at present one of the common sources of this type of timber. Authentic specimens of these four species have been obtained by the courtesy of the Forestry Research Department, Ibadan, and the extraction of each with light petroleum has been examined.furnishing a valuable timber known as '( gedunohor." Authentic specimens of this gave " @ "-sitosterol and either an unsaturated lactone, double m. p. 157"/218", [aID2O -M", which we name gedunin, or a methyl ester, m. p. 197", In no case were both of these found in the same specimen. It has not yet been possible to correlate botanical and chemical variation in this species.E. candoleii is not common in trade. The wood is denser than water, being locally known as " sapele wood-sinker." The only crystalline material obtained from the specimen examined was '( p "-sitosterol.E. cylindricurn, the most important commercial species, furnishes the wood known as " sapele mahogany,'' much used in the manufacture of plywood. It is distinguished by a fragrant smell and yields a volatile oil on steam-distillation. Extraction gave '( ',sitosterol and a crystalline lactone, m. p. 241", [aID2O -4", which we name entandrophragmin.E. utile, which has a softer timber, gave with light petroleum (' p "-sitosterol, entandrophragmin, and a fourth lactone, utilin, m. p. 278", [aID2O -355.5".Further extraction of the wood with acetone then gave methyl angolensate.Analyses of gedunin agree with the formula C2,H34, ,,O,,QCH,*OH, supported by an X-ray molecular-weight determination of the dihydro-derivative which crystallises without solvent. The absorption spectrum suggests the presence of ester or lactone groups. Absorption bands at 1500 and 875 cm.-l may be due to the presence of a furan ring, also indicated6 by nuclear magnetic resonance absorption at -70 and -95 C.P.S. Steam-distillation in the presence of alkali gave furan-3-aldehyde.Methyl angolensate, C2,H2,05,+H20 gave an infrared spectrum indicating the presence of a lactone and an ester, and bands referable to a furan ring, as in gedunin. Alkaline E. angolense is a botanically variable species -43", which we name methyl angolensate. (12 kg.) gave an extract (43 g.) which partly crystallised. The solid fraction crystallised from ethanol to give utilin (7 g.), m. ...

Some reactions of gedunin are described, and it is shown that they are explained by a structure (11) similar to that recently proved for limonin.RECENTLY we described 1 the isolation of gedunin from the timber of Entandrophragma angolense. The formula C28H34(36)07 was assigned to this compound, and it was shown that on hydrogenation over palladised charcoal it gave a dihydro-derivative, which we have also obtained as a natural product from several timbers2 It was also shown that on steam-distillation from alkali gedunin gave furan-3-aldehyde which was isolated as its dinitrophenylhydrazone. The reactions now described indicate that the formula is C,,HM07.Gedunin shows absorption maxima in the ultraviolet (Am,, 215 and 335 mp, log E 4-12 and 1.8) and in the infrared region (1668 cm.-l) consistent with the presence of an a@unsaturated ketone group, and gives a red dinitrophenylhydrazone. The spectrum of dihydrogedunin does not show these characteristics, but has a new band a t 1709 cm.-l, suggesting that it is the corresponding saturated ketone. The maximum at 215 mp is due to absorption by both the @-unsaturated ketone group and the furan ring. When the spectrum of dihydrogedunin, which still has the furan ring (vmax. 1502 and 875 cm.-l), is subtracted from that of gedunin, the maximum for the unsaturated ketone appears at 227 mp (log E 4-0).The molecular-rotation difference between gedunin and dihydrogedunin is -173", in agreement with the change of -162" between 1,2-dehydrohinokione and hinokione, a 3-0xo-diterpene.~ (In ref. 1 the rotation of gedunin and of dihydrogedunin is given with the wrong sign, asinstead of +). Reduction of gedunin with sodium borohydride gave an alcohol which on re-oxidation with chromic acid in acetone gave dihydrogedunin. The molecular-rotation difference between dihydrogedunin and the borohydride reduction product was -110", in agreement with the change of -85" between p-amyrone and @-amyrin. This unusual reduction of an unsaturated ketone to the corresponding saturated alcohol has been reported by Albrecht and Tamm5 in the case of cholest-1-en3-one, and we consider that the evidence suggests that gedunin is a 3-oxo-Al-triterpene derivative.The maximum of cholest-1-en-3-one is at 230 mp (log E 4.0).Further evidence on this is described below.

Baccatin-I11 (3), -1V (4, -VI (7), and the l-dehydroxy derivative of baccatin-IV are taxane derivatives with an oxetan ring.RECENTLY taxol (1),1 a natural product with potent antileukemic and tumour inhibiting properties, was shown to be a taxane derivative with an oxetan ring. This ring system in natural products is rare. One other taxane derivative containing it is baccatin-V (2) .2 p3The structures of further oxetan-containing taxanes have now been determined. They are baccatin-IV4 (5), C,,H,-014, m.p. 254-255" (decomp.), [ a ] D + 19O, Amax 219nm, E 5000 ; 1-dehydroxybaccatin-IV (6) , C,,H,,O,,, m.p. 286" (decomp.), [a],, + 5O, Amax 218 nm, E 7000; baccatin-IV (7), 274, and 282 nm, E 17,600, 860, and 640; and baccatin-VII (8), C36H5,0,4, m.p. 270" (decomp.), [a]= + go, hmax 218 nm, E 2500. C,,H,~O,*J "*p* 244-245" (decomp.)~ [ a ] ~ -5') Amax 225,