4 ヒキオコシカルス培養細胞におけるUrseneおよびOleanene系トリテルペンの生合成

抄録

We report the biosynthesis of oleanene- and ursene-type triterpenes, oleanolic acid (7), maslinic acid (8), 3-epimaslinic acid (9), ursolic acid (10) and 2α-hydroxymaslinic acid isolated from the Isodon japonicus tissue cultures. 3-Epimaslinic acid was biosynthesised from (8) via 3-oxo derivatives, and then the mechanism involving cyclization of (3R)-2,3-oxidosqalene can be excluded in the biosynthesis of 3α-hydroxytriterpene. The ^<13>C-labelling patterns elucidated by ^<13>C NMR spectroscopy in these triterpenes synthesised from (4-^<13>C)mevalonic acid and (1,2-^<13>C_2)AcONa. The results are entirely in accord with Ruzicka's hypothesis for cyclisation of squalene to β-amyrin (37→38→39→40→41). Furthemiore the biosynthesis of ursene-type triterpenes proceed along a route (37→38→39→40→42), and an alternative mechanism involving an intermediate (43) for α-amyrin can be excluded.