84 沖縄産Theonella属の海綿より単離した新規環状ペプチドの構造(口頭発表の部)

概要

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During our studies on bioactive substances from Okinawan marine organisms, we have now isolated five novel cyclic peptides from the extracts of the Okinawan marine sponges of the genus Theonella. Konbamide (1) is a unique hexapeptide containing the unknown amino acid. 2-bromo-5-hydroxy-tryptophan (BhTrp), and possessing an ureido linkage. Keramamide A (2) consists of six amino acid residues, one of which was unknown N-methyl-6-chloro-5-hydroxytryptophan (MeCht), and also contains an unusual ureido bond like 1. Three novel peptides, keramamides B-D (3-5), are structurally unique with the unusual amino acid, BhTrp, and three modified amino acid residues, α,β-unsaturated amide group, an oxazole ring, and α-keto-β-amino acid moiety. The structures of 1-5 were fully established on the basis of extensive spectroscopic analyses including several types of 2D NMR as well as FAB MS/MS experiments. The absolute stereostructures of 1-5 were revealed by the chiral GC and HPLC analyses. Konbamide (1) showed calmodulin antagonistic activity (IC_<50> 10^<-4>M). while keramamide A (2) inhibited sarcoplasmic reticulum Ca^<2+>-ATPase (IC_<50> 3×10^<-4>M). Keramamides B-D (5×10^<-8>M) completely inhibited the superoxide-generation response of the human neutrophils elicited with an fMLP.
天然有機化合物討論会の論文
1991-09-07