128(P-72) トウモロコシの宿主特異的毒素PM-toxin AおよびBの立体選択的全合成(ポスター発表の部)

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PM-toxin, a corn host-specific pathotoxin produced by the fungal pathogen Phyllosticta maydis, was revealed to be the cause of major epidemics of Northern T-corn leaf bright disease in the United States. PM-toxin A and B, major T-corn pathotoxins, have quite unique structures containing a number of characteristic aldol structures on linear C33 chains. We present here the first and highly stereoselective total synthesis of PM-toxin A and B starting from D-lactate (5), which involves three cross-aldol reactions and the regioselective organoselenium-mediated reductive cleavage of four and three consecutive α,β-epoxy ketone units as the key steps. Enantiomerically pure three segments, the epoxy ketone (7), epoxy aldehyde (11) and MPM-protected epoxy ketone (14), were highly stereoselectively synthesized from the common starting material D-lactate (5), respectively. By the cross-aldol reactions of these segments and convergent coupling reactions, the key tetrakis-epoxy ketone (25) and the tris-epoxy ketone were successfully synthesized. The crucial organoselenium-mediated reduction of the tetrakis-epoxy ketone (25) and the tris-epoxy ketone with Na[PhSeB(OEt)_3] occurred cleanly and efficiently to give PM-toxin A and B in high yields, respectively.
天然有機化合物討論会の論文
2000-10-01