26 植物成長促進作用を有する環状糖脂質カロニクチンAの全合成(口頭発表の部)

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Calonyctin A isolated from Calonyction aculeatum L. House (evening-glory) has a potent promoting activity on the plant growth. One of the homologue 1 of calonyctin A has a unique 22-memberd macrolidic structure, which consists of 11-hydroxytetradecanoic acid and four deoxygenated monosaccharides. In order to investigate the mechanism of its physiological activity and assign the absolute configuration of fatty acid, we planned to synthesize 1 and its analogues. We found that an interglucosidic acetal of phenyl 1-thio-β-laminaribioside 6 was a good starting material for the synthesis of 1. After allylation, the fully protected disaccharide 7 was treated with PPTS in MeOH-CHCl_3 and subsequently with BH_3・Me_2NH-BF_3・OEt_2 in CH_2Cl_2, giving the 2,6,2',6'-tetraol 9. A key disaccharide intermediate 5 was prepared by tosylation of 9 and subsequent benzoylation and NaBH_4-reduction of the tosyl groups in 48% overall yield. Coupling of 5 and monosaccharide acceptor 13 with NIS-TfOH gave the trisaccharide derivative 14. After saponification of three ester functions in 14, the resulting 15 was subjected to intramolecular esterification by a mixed anhydride procedure under high-dilution conditions in toluene to give a macrolide. Although two hydroxyl groups are presented, 15 afforded desired 22-membered macrolide 16 as a single product in the yield of 60%. Final L-rhmnosylation of 16 with 4 furnished the tetrasaccharide17, of which de-O-allylation followed by estification with (2R,3R)-3-O-benzyl-2-methylbutyric acid and by hydrogenolysis gave 1.
天然有機化合物討論会の論文
1999-09-01

26 植物成長促進作用を有する環状糖脂質カロニクチンAの全合成(口頭発表の部)

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