77(P57) テンサイ苗立枯病拮抗細菌Xanthomonas sp. SB-K88株が生成する抗生物質xanthobaccin Aの構造解析(ポスター発表の部)

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Xanthomonas sp. strain SB-K88 that has originally been isolated from a fibrous root surface of a sugar beet endangered to infection with Polymyxa betae has been found to deppress sugar beet damping-off disease, and the active substance named xanthobaccin A has already been isolated from culture filtrate of the bacterium as a structurally unknown antibiotic that drastically calmed damping-off disease in a sugar beet seedling pot assay. We did structural elucidation of xanthobaccin A by spectroscopic analyses and chemical derivatization, including its relative configuration. Xanthobaccin A (1), having a chromophore to show its unique UV and fluorescence λmax, was formulated in FD- and FAB-HR-MS to be C_<29>H_<38>N_2O_6. In the ^<13>C-NMR including some 2D-NMR (HMQC, HMBC and DEPT-HMQC) spectra, all of the carbons of 1 were characterized to have a unique 5,5,6-tricyclic carbon skeleton consisting of two C12-acetogenine units and also an α,β-hydroxyornithine part. These two partial structures were combined via an amidebond and a tetramic acid-like cyclization to form the macrocyclic lactam molecule. The acetogenine class hydrophobic part involving the 5,5,6-tricyclic structure was converted to the dicarboxylic acid dimethyl ester derivative (2) by acidic methanolysis of 1, and its structure was also proven by the NMR analyses. Consequently, structure 1 was elucidated to be a new macrocyclic lactam antibiotic having a new carbon skeleton. Compound 1 was closely related with an antibiotic, ikarugamycin (3), isolated from Streptomyces phaeochrmogenes var. ikaruganensis in their planar structures and biogenesis; therefore compound 1 is also considered to have a wide physiologically active spectrum against several organisms as does 3.
天然有機化合物討論会の論文
1998-08-31

77(P57) テンサイ苗立枯病拮抗細菌Xanthomonas sp. SB-K88株が生成する抗生物質xanthobaccin Aの構造解析(ポスター発表の部)

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