34 植物培養細胞におけるphytosterolの生合成 : ^<13>C-signalの帰属と側鎖生合成における立体特異性

抄録

^<13>C signals of C-26 (pro-R methyl group at C-25) and C-27 (pro-S) of sitosteryl acetate and its 24β epimer, clionasteryl acetate, which were chemically derived from ^<13>C-enriched isofucosteryl acetate (3-II), were assigned using the 'INADEQUATE' ^<13>C-NMR method. 3-II was obtained from the cell cultures of Physalis peruviana grown in the presence of [1,2-^<13>C]AcONa, followed by acetylation. As C-26 of 3-II is known to be derived from C-2 of mevalonate (MVA), the signals at δ 20.93 and δ 21.01 of 3-II could be assigned to C-26 and C-27, respectively. 3-II was then converted into a mixture of [^<13>C, 24-^2H, 28-^2H]sitosteryl acetate (10) and [^<13>C, 24-^2H, 28-^2H]clionasteryl acetate (11) by the catalytic deuteration. ^<13>C-^<13>C coupled signals due to C-27 of the respective 10 and 11 were observed selectively in the 'INADEQUATE' spectrum of the mixture. Thus the signals at δ 18.98 and δ 19.75 in 10 and the signals at δ 18.92 and δ 19.53 in 11 could be assigned to C-27 and C-26, respectively. The ^<13>-labelling patterns of C-26 and C-27 of several typical phytosterols, sitosterol (6), stigmasterol (8), α-spinasterol (12) and 24-methylene cholesterol (2), biosynthesized from [1,2-^<13>C]-AcONa in the cell cultures of Physalis peruviana, Bupleurum falcatum, Dioscorea tokoro, and Isodon japonicus were also examined. In all cases, C-26 (pro-R methyl group) originated predominantly from C-2 of MVA and C-27 from C-6 of MVA.