Kiyoshi Isono

Chemistry of the neopolyoxins, pyrimidine and imidazoline nucleoside peptide antibiotics

Abstract New chitin synthetase inhibitors, neopolyoxins A, B, and C were isolated from the culture filtrate of Streptomyces cacaoi subsp. asoensis. Their absolute structures have been established on the basis of chemical and spectroscopic evidence. They are structural analogs of the polyoxins. As a nucleobase, neopolyoxin C possesses uracil, while neopolyoxins A and B contain the imidazoline moiety. A ring contraction reaction of pyrimidine nucleoside into imidazoline nucleoside played a key role in the structure determination of the nucleoside moiety. A similar transformation was suggested for the biosynthesis of neopolyoxins A and B.

Structures of neopolyoxins A, B, and C

Abstract The absolute structures of fungal chitin synthetase inhibitors, neopolyoxins A, B, and C were determined as 1, 2, and 3 respectively on the basis of chemical and spectroscopic evidence.

The structure of enopeptins A and B, novel depsipeptide antibiotics

Abstract The structures of enopeptins A and B, novel depsipeptide antibiotics with 1,3,5,7,9-decapentaene-1,10-dicarboxylic acid and 2-amino-3-hydroxycyclopent-2-enone in a side chain, were determined by chemical and spectroscopic means.

Molecular shape analysis and activity of tautomycin, a protein phosphatase inhibitor

Abstract Tautomycin, a well-known protein phosphatase inhibitor, exists in two forms (acid anhydride and diacid). We successfully isolated them and proved that diacid is the real active form of tautomycin. The molecular shape-activity relationship of tautomycin and its conformational analysis are also described.

13C-NMR evidence for the biosynthetic incorporation of acetate into minimycin and compounds related to krebs cycle

In recent years, application of carbon 13 NMR (CMR) for biosynthetic study utilizing 13C-labeled acetate has been extensively developed for polyketide and isoprenoid compounds. However, its application to the biosynthesis of the compounds derived from the Krebs cycle has been limited because of the high isotope dilution and extensive randomization through the cycle. To our knowledge, the maleimide ring of showdomycin [2] and the a-aminoadipoyl group of penicillin Nand cephalosporin C [3] are the only examples of this class of compounds utilizing [1or 2-13C]acetate for their biosynthetic study. We considered that this difficulty may be overcome by utilizing doubly-labeled [1 ,2-13C]acetate from the following reasons. First, CMR analysis depends not on enrichment of signals, but on 13C-13C coupling which appears as independent satellite bands. Therefore, high incorporation may not be required for analysis. Second, one cleavage of the C-C bond originating from the same acetate unit occurs, there would be no coupling observed. Thus, the extensive recycling through the Krebs cycle or its shunt pathways would not result in the complex coupling pattern. As an example, we report herein the utilization of [ 1 ,2_1 3C]acetate for the biosynthetic study of the oxazine ring of the C-nucleoside antibiotic, minimycin [4,5], which has recently been found to be biosynthesized from a-ketoglutarate [ 6 ]. Succinic acid and fumaric acid from the culture filtrate as well as glutamic acid from the cell protein were also analyzed to confirm the coupling pattern.

Synthetic studies on tautomycin synthesis of Segment B

Abstract The synthesis of Segment B corresponding to the C26–C17 portion of tautomycin was accomplished by coupling reaction between the epoxide (Sub-segment B-1) and the dithiane (Sub-segment B-2). The degradation product of tautomycin corresponding to the C26–C19 portion was also synthesized from Sub-segment B-1.

Synthesis of guanine 7-oxide, an antitumor antibiotic from streptomyces species

Abstract The first synthesis of the antitumor antibiotic guanine 7-oxide (VI) has been achieved via a 4-step route starting from phenacyl bromide (I) and the nitropyrimidone III and proceeding through the intermediates IVe and Ve.

Specific binding of chartreusin, an antitumor antibiotic, to DNA

It was evidenced that the binding of the agent is not at random and correlates to the sequence on DNA stretch.

The structure of lipopeptin a

Abstract The structure of lipopeptin A, an antifungal peptolide antibiotic was determined as 1 on the basis of chemical and spectroscopic evidence.

Differentiation Inducing Phosphatidyl Choline(s) from the Embryos of Rainbow Trout (Salmo gairdneri): Isolation and Structural Elucidation'

Phospholipid which is able to induce the differentiation of some undifferentiated tumour cells was isolated from the rainbow trout (Salmo gairdneri) embryos.