21 Heliangineの構造
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Heliangine (I), C_<20>H_<26>O_6; m.p. 227-229°; (α)^<25>_D-110°; λ_<max> 207.5 mμ(ε: 23,800); υ_<max> 3450, 1754, 1660 cm^<-1>, contains three olefinic bonds. When I was hydrogenated over Pd-C, the exocyclic methylene conjugated with γ-lactone was saturated at first, resulting dihydroheliangine (II); 1770 cm^<-1> (γ-lactone); τ8.9 (C-CH_3). I was hydrolysed with Ba(OH)_2 to give tiglic acid and helianginol (IX), C_<15>H_<20>O_5, containing two secondary hydroxyl groups. Hydrolysis of tetrahydroheliangine (III), obtained by hydrogenation of I, afforded α-methylbutyric acid and dihydrohelianginol. The last olefinic bond was hydrogenated over PtO_2 to give two isomeric hexahydroheliangine (IVa, b) and deoxyhexahydroheliangine (V). A pair of two coupled proton signals at τ 3.5 (d, J=11 cps) and τ4.7 (d, J=11 cps) of III is disappeared in either IVa or IVb, and the latter shifted to τ 4.85 (m). The carbon carrying the lactonic oxygen therefore must be neighbored on the last olefinic group. The hydroxyl group of III also neighbored on the olefinic group, for III afforded the α,β-unsaturated ketone (VI); λ_<max> 246 mμ(ε: 5950) by oxidation with CrO_3. As VI was isomerined to hydroxydienone compound (VII); λ_<max> 249.8 mμ(ε: 9430) by treating with acid, the partial structure A was assumed. The dehydrogenation of II or III afforded two azulenic compounds X and XI. It can be therefore concluded reasonably that I contains a germacrane lactone. Now we decided on the basis of a biosynthesis that constitution I is more reasonable for heliangine than another possible constitution XII.
- 天然有機化合物討論会の論文
- 1966-09-15
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