Studies on The Synthesis of Sesquiterpenes as Host-specific Phytotoxins Directed towards Novel Insecticides.

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Studies on phytotoxins produced by host-specific fungi againdt plants have been paid much attention to clarify the mode of action as well as to develope new insecticides. The amount of these pathogenic toxins, however, not sufficient for biological study, because they are not much available from natural sources. The target of this project is the synthesis of these pathogenic sesquiterpenes to afford natural isomers and their analogs in optically pure forms in substantial amount for biological study.Starting from the hydroxyester with 98.4% e.e. prepared by the asymmetric reduction with bakers yeast, chiral synthesis of sporogen-AO 1( 13-desoxyphomenone ) was achieved in overall 8.4 % yield through 20 steps. By the establishment of this efficient method, general route to afford these pathogenic eremophilane sesquiterpenes was explored. Thus, gigantenone, epi-gigantenone, phomenone ,phase-olinone and analogs were obtained. Using these samples, biological studies is going on, and preliminary experiment showed that even epimer has 60-70% activity of natural isomers. Further studies may reveal biological meaning of these sesquiterpene as pthogens against plants and as sporogenic substances against fungi.