54(P-25) 水生不完全糸状菌Clavariopsis aquaticaから得られた新規環状デプシペプチドの構造及び立体配座解析(ポスター発表の部)

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In the course of our screening for antifungal antibiotics from various fungi, new cyclic depsipeptides named clavariopsins A (1) and B (2) were isolated from the fermentation broth of Clavariopsis aquatica. The molecular formula of 1 was determined to be C_<59>H_<95>N_9O_<14> by high-resolution FAB MS. The IR spectrum of 1 suggests the presence of ester, hydrogen-bonded carboxyl, and amide groups, respectively. In the ^1H, ^<13>C NMR, and HMQC spectra, the signals due to α protons, NH protons, N-methyl groups, and carbonyl carbons of amino acid residues were observed. These data suggested that 1 is a highly methylated peptide or peptide-like compound. DQF-COSY and HOHAHA analyses of 1 revealed the partial structures of nine amino acid residues and an α-hydroxy acid residue. These partial structures and the rest of the molecule were connected by a HMBC spectrum to give the gross structure of 1. The gross structure of 2 was determined in the same way as that for 1. In 2, the N-methyl group of MeVal^3 of 1 was replaced with the new NH group. To assign the absolute configuration of the amino acid constituents in 1, we applied the "advanced Marfey's method". An acid hydrolysate of 1 was derivatized with D- and L-FDLA, and the analyzed by LC/MS using negative-mode ESI. The deprotonated pseudomolecular ion [M-H] of the amino acid constituents derivatized FDLA was detected in the mass chromatograms. By comparing mass chromatograms of L-FDLA and DL-FDLA derivatives, we concluded that all the nine amino acid constituents of 1 have the L-configuration. The absolute configuration of 2-hydroxyisovaleric acid residue of 1 was determined to be R by chiral HPLC analysis of the hydrolysate of 1. The conformation in solution of 1 was analyzed by using NMR and computational method. From the ROESY experiment, amide bonds of the MeVal^3-Val^4-MeAsp^5-MeIle^6-MeIle^7, Gly^8-MeVal^9-Tyr(OMe)^<10>, and O-Val^1_Pip^2 sequences have trans orientation and that of Pip^2-MeVal^3 has cis. Temperature dependence of NH protons of 1 in ^1H NMR showed that NH proton of Gly^8 was hydrogen-bonded and that of Val^4 and Tyr(OMe)^<10> were not. On the basis of these results, conformational search of 1 using a MacroModel software is in progress.
天然有機化合物討論会の論文
2000-10-01

54(P-25) 水生不完全糸状菌Clavariopsis aquaticaから得られた新規環状デプシペプチドの構造及び立体配座解析(ポスター発表の部)

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