91 新規テトラテルペノイドKS-505の構造決定(口頭発表の部)

概要

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KS-505(1) is a potent inhibitor of calmodulin dependent phosphodiesterase, elaborated by streptomyces argenteolus. Molecular formula of 1 (C_<61>H_<88>O_<17>) was determined by high resolution FAB-MS, but further analysis was unsuccessful owing to its intramolecular equilibrium. Two isomeric methyl ester (2,3) were prepared, which correspond to the tautomeric structures of 1. Detailed studies using homo- and heteronuclear two dimensional NMR spectroscopy on 2, including HMQC-HOHAHA method, exhibited the structure shown in Fig. 3. Methanolysis of 2 afforded lactone 4, which was confirmed to be D-sugar by comparison with synthetic authentic sample. Analysis of NOE data around the sugar moiety and aglycon moiety, revealed the absolute stereochemical structure of 2. 3, which is an epimeric mixture of methoxy group, was elucidated to be shown in Fig. 1 by the same manner as in 2. Finally, the position of methoxycarbonyl group which had been exist in 1, was determined by the studies of MS fragmentation of 1 and of NMR analysis of aglycons. 1 is a novel tetraterpenoid with a unique 2-O-methyl sugar, and from the biosynthetic point of view, origin of sec. methyl groups at C-1 and C-12 position is interesting and worth investigating.
天然有機化合物討論会の論文
1991-09-07