Novel thiazole and oxazole containing cyclic hexapeptides from a waterbloom of the cyanobacterium Microcystis sp. |
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Authors: | Avi Raveh Zoharia Evron Shmuel Carmeli |
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Institution: | a Raymond and Beverly Sackler School of Chemistry and Faculty of Exact Sciences, Sackler Faculty of Medicine, Tel Aviv University, Ramat-Aviv, Tel-Aviv 69978, Israel b The Department of Clinical Microbiology and Immunology, Sackler Faculty of Medicine, Tel Aviv University, Ramat-Aviv, Tel-Aviv 69978, Israel |
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Abstract: | Eight novel thiazole and oxazole containing cyclic peptides, microcyclamides GL616, GL582, GL614A, GL614B, GL614C, GL546A, GL546B, and GL628, as well as the known microcyclamide A, were isolated from the hydrophylic extract of a Microcystis sp. water-bloom collected in Gilboa reservoir, Valley of Armageddon, Israel. The planar structure of the compounds was determined by homonuclear and inverse-heteronuclear 2D NMR techniques as well as high-resolution mass spectrometry. The absolute configuration of the asymmetric centers of the amino acids was studied using Marfey's method for HPLC following ozonolysis, hydrolysis and derivatization with Marfey's reagent. This is the first example where acidic and modified amino acids are incorporated in this group of ribosomally biosynthesized metabolites. |
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Keywords: | Cyanobacteria Microcystis Cyclichexpeptides Natural products |
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