摘要:
C hem ical Communications NUMBER 1311966 6 JULY Warburgin, a New Sesquiterpenoid of the Eremophilane Group By C. J. W. BROOKS and G. H. DRAFFAN (Chemistry Department, University of Glasgow, Glasgow, W.2) EXTRACTION of the heartwood of Warburgia ugandensis Sprague (Canellaceae) has afforded a number of new sesquiterpenoids, including a characteristic yellow crystalline keto-ester for which we propose the name warburgin. Its structure and probable absolute configuration as (I) are indicated by the following evidence. Warburgin, C16H1604 (analysis and mass spec- trum) sublimed in vucuo as prisms, unstable towards air andlight, m.p. 159-161'; [a]D + 120" (CHC1,); Ymax (CCl,) 3156 (weak: vCH, furan a-CH), 1734 (vce0 of ester), 1679 of conjugated ketone), 1566 (furan) cm.-l;A max (EtOH) 370 mp ( E , 20,000).In the 60 Mc./sec. n.m.r. spectrum (CDCl,), signals were observed at T 9.17 (3H at C-15) ; 8.76 (doublet, J = 7 c./sec. : 3 H at C-14) ; 7-39 (quartet, J = 7 c./ sec.: 1 H at C-4); 7-31 (doublet, J = 17 c./sec.: 1 H at C-6); 6.72 (doublet, J = 17 c./sec.: 1 H at C-6); 6.10 (3 H of OMe); 3-86 (doublet, J = 9 c./ sec. : 1 H at C-2) ; 3.29 (1 H at C-9) ; 2.91 (doublet, J = 9 c./sec.: 1 H at C-1); 1.96 (1 H at C-12). Alkaline hydrolysis of warburgin gave a mixture of two acidic products, treatment of which with diazomethane gave a difficultly-separable mixture of (I) and an unstable isomer (mass spectometry) closely resembling (I) in spectroscopic properties. This product is possibly the 4-epimer of (I) but its identification is not yet complete. Hydrogenation of warburgin in ethyl acetate with a 10% palladium-charcoal catalyst gave tetrahydrowarburgin (11), C1,H,,,O4 (analysis and mass spectrum), m.p.172-173"; [a]D + 50" (CHCI,); Vmax (CCl,) 1730 (v, of ester), 1721 (vc=o of saturated ketone) cm.-l; Amax (EtOH) 255 mp ( E , 2650). The mass spectrum included a base peak at m/e 152 resulting from "retro-Diels-Alder" fragmentation [as (XII; R = C02Me)]. Analo- gous peaks were observed in the spectra of the related compounds (111-VII) described below. Lithium aluminium hydride reduction of (11) gave an unstable diol (111), C15H22O3 (mass-spectral molecular ion, m/e 250); [a]D + 62" (CHCl,); Vmax (CCl,) 3624, 3615 cm.-l Oxidation of (111) with chromium trioxide-pyridine yielded the keto- aldehyde (IV) C1,H1,03 (analysis and mass spectrum), m.p.131-135'; [aID + 58' (CHC1,) ; Vmax (CC1,) 2724 (vGX of aldehyde), 1718 ( v ~ = ~ of ketone), 1690 (vc=o of aldehyde) cm.-l; Amax (EtOH) 271 mp (E, 2600). Wolff-Kishner reduc- tion of (IV) gave a furano-hydrocarbon (VII) isomeric with natural furanoeremophilane (IX) of known absolute configuration.1 Catalytic hyd- rogenation of (VII) with platinum oxide in acetic acid afforded two major products (VIII) both different (by g.1.c.) from an authentic sample of tetrahydrofuranoeremophilane (X) of known abso- lute c0nfiguration.l Combined gas chromato- graphy-mass spectrometry showed that the two compounds (VIII) were isomeric with (X). The above chemical and spectroscopic results appeared to require formulation of warburgin as the eremophilane derivative (I) or its 4-epimer.Conversion of (11) into new isomers of furanoeremo- philane and tetrahydrofuranoeremophilane sug- gested a possible trans-ring fusion in this compound and its congeners. At this stage, Dr. K. H. Overton394 CHEMICAL COMMUNICATIONS H (VIII) xcb H kindly informed us of the 'H bLq+ (XII) (then unpublished) constitution of furanoligularenone (XI) as eluci- dated by Professor G. Ourisson and his co-workers.2 The two compounds were correlated as follows. Reduction of the thioacetal (V), characterised by its infrared, n.m.r., and mass spectra, gave the furanoketone (VI) , C15H2002 (mass-spectral mole- cular ion, 232) ; m.p. 84-88O; Vmax (KC1 disc) 1711 ( v ~ = ~ of ketone), 1650 and 1563 (weak) cm.-l (furan), identical with a sample of furanoligula- ranone [the hydrogenation product of (XI)].The identity was further established by combined gas chromatography-mass spectrometry, and by com- parison of the optical rotatory dispersion curves measured in methanol. Compounds (11), (IV), and (VI) all showed negative Cotton-effect curves [e.g., (11): $304 -4180", 5b2,0 + 5300", a = -95). Provided that the presence of the furan ring does not invalidate the octant rule, absolute configura- tions a t C-4 and C-5 are implied as indicated., The shifts observed for the n.m.r. signals of the P S (Iv) I 4-methyl group in (11), (IV), and (VI), measured in benzene,4 are compatible with these configurations. The assignments are probable but are not rigorous. Experiments aimed at confirming the configuration at C-10 in (11)-(VII) are in hand.Two other sesquiterpenoids, warburgiadione and drimenol, from the same heartwood merit brief mention. Warburgiadione (C16H1802), a yellow crystalline diketone, m.p. 127-128", [aID + 25" (CHCl,) ; vmax( CCl,) 1686,1659 crn.-l;hmax (EtOH) 292 mp ( E , 21,500), will be the subject of a later Communication. The isolation of drimenol5 pro- vides an interesting chemotaxonomic link between the Winteraceae and Canellaceae, confirming their relationship despite the considerable morphological and geographical gap between the families.6 Combined gas chromatography-mass spectro- metry was carried out with an Atlas CH4 instru- ment (Houston) modified by Dr. Ryhage, and with an LKB 9000 instrument (Glasgow). (Received, May 17tk, 1966; Corn. 332.) 1 L. Novotng, J. Jizba, V. Herout, F. Sorm, L. H. Zalkow, S. Hu, and C. Djerassi, Tetrahedron, 1963, 19, 1191. a F. Patil, J. Lehn, G. Ourisson, T. Tanahashi, and T. Takahashi, Bull. Soc. chim. France, 1965, 3086. 8 C. Djerassi and J. E. Gurst, J . Amer. Chem. Soc., 1964, 86, 1756. tj H. H. Appel, C. J. W. Brooks, and K. H. Overton, J . Chem. Soc., 1959, 3322. 6 J. Hutchinson, "The Genera of Flowering Plants", Vol. I, p. 63, Oxford University Press, 1964. J. D. Connolly and R. McCrindle, Chem. and Ind., 1965, 379; N. S. Bhacca and D. H. Williams, Tetrahedron Letters, 1964, 3127.
ISSN:0009-241X
DOI:10.1039/C19660000393
出版商:RSC
年代:1966
数据来源: RSC