Ebenaceae extractives. Part 6. Ehretione, a bisnaphthoquinone derived from plumbagin and 7-methyljuglone

摘要

2546 J.C.S. Perkin IEbenaceae Extractives. Part 6.l Ehretione, a Bisnaphthoquinonederived from Plumbagin and 7-MethyljugloneBy Terence J. Lillie, Oliver C. Musgrave," and Douglas Skoyles, Chemistry Department, The University, OldAberdeen AB9 2U EEhretione ( I ) , isolated from Diospyros ehretioides, is the first example of a natural quinone which contains bothplumbagin and 7-methyljuglone units.IN the course of separating the pigments of the wood ofDiosfiyros ehrefioides Wall we have obtained a newbisnaphthoquinone , C,,H,,O,, for which we propose thename ' ehretione ' and the structure (1). Ehretioneundergoes little fragmentation in the mass spectrometerbut the formation of ions with m/e 134 and 106 suggeststhat it contains a 7-methyljuglone unit. The n.m.r.spectrum confirms this, the signals at 6 2.46, 7.11, 7.51,and 11.86 resembling closely those1 from unit A ofdiospyrin (2).The OH chemical shift (6 11 36) indicatesthat unit A of ehretione carries an aryl group at C-2,and the remaining signals establish that this substituentis a plumbagin unit, as in structure (1). Thus the signalsat 6 2.23 and 6.85 resemble closely those shown by themethyl and olefinic protons of elliptinone (3), and the( 1 ) X=H, Y=Me( 2 ) X=Me, Y=H0(3)position of the AB quartet centred a t 6 7.63 and 7.73resulting from the aryl protons at C-7' and C-8' is similarto that (6 7.73) of the singlet produced by the corre-sponding protons of elliptinone. The 6 value (12.44) ofthe C-5' hydroxy-proton signal of ehretione is con-siderably higher than that calculated3 (6 12.22) on thebasis of the observed shift (6 12.11) for the correspondinghydroxy-proton of diospyrin. I i e attribute this ano-maly to the absence of a methyl group a t C-7' ofehretione, which results in a decrease in the twisting ofthe bisnaphthoquinone system.Both the enhancedmesomeric effect of the quinonoid substituent at C-6'and the proximity of the C-1 carbonyl group would helpto deshield the hydroxy-proton.EXPERIMENTALEhretione (5,5'-Dihydroxy-2' , 7-dii~etlzyl-2,6'-bisna~htJz o-quinone) (1) .-The band located between lupeol andmamegakinone in the thin-layer chromatogram of thesoluble material from Diospyros eh vetioides afforded a solidwhich crystallised from light petroleum to give elwetione( 5 mg) as orange needles, 1n.p.232" (decornp.) (Found:A$, 374.0785. C,,H,,O, requires 374.0790), vmaU. (KBr)1665 and 1642 (quinone C=O and hydrogen-bondedquinone GO), and 1602 cm-l ( G C ) , h,,, (EtOH) 431 nm(log E 3.41), A i d . 245 nin (log E 3.89), 6 (CDC1,) 2.23br(3 H , s, 2'-CH,), 2.46 (3 H, s, 7-CH3), 6.85br (1 H , s , H-3'),7.07 (1 H, s, H - 3 ) , 7.11br (1 H, s, H-6), 7.51br (1 H, s, H-8),7.63 and 7.73 (2 H , ABq, J 8 H z , H-7' and -83, 11.86 (1 H,s, 5-OH), and 12.44 (1 H, s, 5'-OH), w / e 374 [loo%, (M)+'],346 [go/,, ( M - CO)+'], 187 [6:4, 134 (50,;), and106 (5%).Elliptinone showed 6 (CDCl,) 2.22br (6 H, s, 2- and 2'-CH,), 6.86br ( 2 H , s, H-3 and -3'), '7.73 ( 4 H, s, H-7, -7', -8,and -87, and 12.48 (2 H , s, 5- and 5'-OH).We thank the S.R.C. and the University of Aberdeen forResearch Studentships.[6/1208 Received, 22nd Jzctte, 19761Part 5, T. J. Lillie, 0. C. Musgrave, and D. Skoyles, J.C.S.2 0. C . hlusgrave and D. Skoyles, J.C.S. Perkin I, 1974, 1128.T. J. Lillie and 0. C. Musgrave, J.C.S. Perkin I, in the press.Perkin I, 1976, 2155