抄録
The inhibitors of biologically active isoprenoid biosyntheses are not only useful as a tool of the study on the biosynthetic pathways, but also used as agricultural chemicals or medicines. This paper will report total synthesis of diplodialide-A which is a steroid hydroxylase inhibitor and screening study on the inhibitors of gibberellin biosynthesis. (I) Total Synthesis of Diplodialide-A The key intermediate(6) was prepared by the reaction of the dianion of ethyl acetoacetate with the bromibe(5). The seco acid(8) was transformed to the thiol ester(9) and its dilute xylene solution was refluxed under argon to give (10). The introduction of a double bond to the γ-position of the β-keto-lactone(11) has been performed by the γ-selenenylation of the dianion of (11) follewd by selenoxide elimination. Both antipodes of (±)-diplodialide-A were synthesized by GLC separation of the diastereoisomeric mixture of the acetal, (15) and (16), and the following reactions. (II) Inhibitors of Gibberellin Biosynthesis Resuspended mycelium of G. fujikuroi was used for tests. In our screening study of the inhibitors of gibberellin biosynthesis, 1-geranylimidazole and 1-decylimidazole showed inhibition of GA_3 biosynthesis at 12.5ppm(66% inhibition) and 6.25ppm(74% inhibition), respectively. These compounds inhibited C-19 oxygenation of (-)-kaurene and kauren-19-ol, but not the transformation of kaurenoic acid to gibberellin.
