15 シロダモから得られた2種のエレマン型新セスキテルペノイドの構造

抄録

Two new methyl esters of sesquiterpenoid (isosericenine having a furan ring and sericea lactone having a hydroxy α,β-butenolide) were respectively isolated from fractions b.p. 136-139° and 139-148℃ in 5 mmHg of the essential oil collected in the steam distillation of the leaves. When the leaves of the same plant was extracted with n-hexane and chromatographed on a silica gel column with the deep precaution of keeping the treating temperature below 60℃, the third methyl ester, sericenine (V) of sesquiterpenoid which has the carbon skeleton of germacrane was obtained. Isosericenine, [α]_DO, have molecular formula C_<16>H_<20>O_3(high resolution mass spectrometry) and partial structure of CH_2=CH-C, CH_3-C, CH_2 CH_2-O-CH_3, and CH_2=C(COOCH_3)-(on the physical and chemical evidences). On the basis of these evidences the isosericenine must be represented by structure (I) or (II). Since the isosericenine produced ujacazulene in a good yield in the dehydrogenation with selenium, it was concluded the isosericenine have structure (I). Sericea lactone, m.p. 150-151℃, [α]_DO, have molecular formula C_<16>H_<20>O_3 (mass spectrometry and elementary analysis) and CH_2=CH-C, CH_3-C, HO-O-O-CH_3, and CH_2=C(COOCH_3)-. Besides, isosericenine was easily oxidized in the stream of air in the presence of PtO_2 catalyst to produce sericea lactone. Therefore, sericea lactone was represented by structure (III). The structure of the third compound, sericenine, was elucidated by leading it into compound (VI), and its detail will be reported later. Isosericenine and sericea lactone are thought to be derived from sericenine.