63(P36) 核酸系抗生物質Herbicidin Bの合成研究(ポスター発表の部)

概要

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Herbicidins are efficient inhibitors of Xanthomonas oryzae, a bacterium which causes rice infection disease. Their structures are consist of adenine and unique furanopyranopyrane, undecose, having the intramolecular hemiacetal linkage. Our synthetic strategy is that herbicidine B (1b) is synthesized from a 2-urose unit and 5'-formyl derivative of adenosine, and the two units will be coupled by aldol-type C-glycosylation induced by SmI_2. First, we developed an efficient SmI_2-induce aldol-type C-glycosylasion reaction with 1-SPh-2-urose derivatives as donors: treatment of 1-SPh-2-urose derivative 11 with SmI_2 in THF at -78℃ gave corresponding 1-enolate which effectively reacted with cyclohexanone to afford a C-glycosides 12 in high yield (α/β=79/21). This method effectively produced 1-enolates of urose derivatives under very mild conditions. We, next, applied the C-glycosylation reaction to the synthesis of Herbicidin B. 1-SPh-2-urose 4 and aldehyde 5 were prepared from D-glucose and adenosine, respectively (Scheme 2, 3). Treatment of 4 with SmI_2 in THF at -78℃ followed by addition of aldehyde 5 gave the desired undecose nucleoside 23, the key intermediate, in 75% yield. It was shown that SmI_2-induced Aldol-type C-glycosidation was effective to the synthetic study toward Herbicidin B. The conversion of the undecose nucleoside 23 into Herbicidin B is currently under progress.
天然有機化合物討論会の論文
1997-07-20