- Molecular basis for trehalase inhibition revealed by the structure of trehalase in complex with potent inhibitors
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Strong inhibitions: The inhibition of trehalases, enzymes which hydrolyze the disaccharide trehalose, is a target for novel antibiotic insecticides. The structures (see picture; C black, N blue, O red, S yellow) of a trehalase in complex with validoxylami
- Gibson, Robert P.,Gloster, Tracey M.,Roberts, Shirley,Warren, R. Anthony J.,Storch De Gracia, Isabel,Garcia, Angela,Chiara, Jose L.,Davies, Gideon J.
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- Pseudoglycosyltransferase catalyzes nonglycosidic C-N coupling in validamycin a biosynthesis
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Glycosyltransferases are ubiquitous in nature. They catalyze a glycosidic bond formation between sugar donors and sugar or nonsugar acceptors to produce oligo/polysaccharides, glycoproteins, glycolipids, glycosylated natural products, and other sugar-containing entities. However, a trehalose 6-phosphate synthase-like protein has been found to catalyze an unprecedented nonglycosidic C-N bond formation in the biosynthesis of the aminocyclitol antibiotic validamycin A. This dedicated 'pseudoglycosyltransferase catalyzes a condensation between GDP-valienol and validamine 7-phosphate to give validoxylamine A 7′-phosphate with net retention of the 'anomeric configuration of the donor cyclitol in the product. The enzyme operates in sequence with a phosphatase, which dephosphorylates validoxylamine A 7′-phosphate to validoxylamine A.
- Asamizu, Shumpei,Yang, Jongtae,Almabruk, Khaled H.,Mahmud, Taifo
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p. 12124 - 12135
(2011/10/09)
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- Synthesis of [7-3H]valienamine, [7-3H]valienone, [7-3H]valiolamine and [7-3H]valiolone from validamycin A
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To investigate the biosynthetic pathway to the cyclitol moieties of acarbose and validamycin A, [7-3H]valienamine, [7-3H]valienone, [7-3H]valiolamine and [7-3H]valiolone were synthesized as plausible precursors. Valienamine together with validamine was isolated from the degradation of validamycin A by Flavobacterium saccharophilum and served as starting material for the synthesis. Validamine was removed partially at the stage of tritylation and completely after the oxidation of the primary hydroxy group at C-7 to the aldehyde. The resulting valienamine aldehyde was reduced with tritiated sodium borohydride to produce [7-3H]valienamine. The latter was converted to [7-3H]valiolamine by a synthetic route described in the literature. The 3H-labeled amines were oxidized to [7-3H]valienone and [7-3H]valiolone, respectively, using 3,5-di-tert-butyl-1,2-bezoquinone (DBQ) followed by hydrolysis with oxalic acid.
- Lee, Sungsook,Tornus, Ingo,Dong, Haijun,Groeger, Stefan
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p. 361 - 372
(2007/10/03)
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- Synthetic studies on antibiotic validamycins. Part 13. Total synthesis of (+)-validamycins A and E, and related compounds
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(+)-Validoxylamine A (1) has been completely synthesized by deoxygenation of the validoxylamine B derivative (6) through formation of the aziridine, nucleophilic displacement with toluenethiol, reduction with Raney nickel, and deprotection. The validoxylamine A derivative (10) obtained was convertible, by glycosylation followed by deprotection, into validamycins A (2), E (3), and their analogues, which constitutes a total synthesis thereof.
- Miyamoto, Yasunobu,Ogawa, Seiichiro
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p. 1013 - 1018
(2007/10/02)
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- Total Synthesis of (+)-Validoxylamine A
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(+)-Validoxylamine A was synthesized by selective deoxygenation of (+)-validoxylamine B derivative, which was obtained by the coupling of the partially protected (+)-valienamine and (1R,2S,5R,7R,8R,9R,10R)-8,9-dibenzyloxy-5-phenyl-4,6,11-trioxatricyclo8.
- Ogawa, Seiichiro,Miyamoto, Yasunobu
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p. 889 - 890
(2007/10/02)
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- Synthetic Studies on the Validamycines. 10. Total Synthesis of DL-Validoxylamines A and B.
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The first synthesis of racemic validoxylamine A (3) and B (4), constituents of antibiotic validamycins, is described.For construction of these types of pseudodisaccharides containing an imino linkage, a coupling reaction of the protected anhydro derivative of DL-pentahydroxy(hydroxymethyl)cyclohexane (5) with the DL-trihydroxy(hydroxymethyl)cyclohexylamine or -cyclohexenylamine (6 or 7) was untertaken.All possible diastereoisomers (four pairs of enantiomeres) formed by the reaction of 5 with 6, employed for synthesis of 4, could be separated by chromatography on silica gel, and the relative configuration in two of the enantiomeric pairs, deduced on the basis of 1H-NMR spectroscopy, were confirmed by identification of one pair with an authentic chiral sample 4.On the other hand, the intermediate enantiomeric pair 13a obtained by a coupling of the appropriate epoxide 5 and amine 7 underwent mainly dehydration with sulfuryl chloride in pyridine to give the pair of enantiomers 19a, one of which was the protected derivative of 3.In contrast, the diastereomeric pair of enantiomers 13b yielded selectively the chloride 18b, which was then transformed into the enantiomeric pair 21b by dehydrochlorination followed by deprotection.
- Ogawa, Seiichiro,Ogawa, Takao,Iwasawa Yoshikazu,Toyokuni, Tatsushi,Chida, Noritaka,Suami, Testsuo
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p. 2594 - 2599
(2007/10/02)
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- SYNTHESIS OF DL-VALIDOXYLAMINE A
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The first total synthesis of DL-validoxylamine A, one of the components of the antibiotic validamycin complex, is described.
- Ogawa, Seiichiro,Ogawa, Takao,Chida, Noritaka,Toyokuni, Tatsushi,Suami, Tetsuo
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p. 749 - 752
(2007/10/02)
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- SYNTHESIS OF SOME RACEMIC ISOMERS OF VALIDOXYLAMINE A
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Two racemic isomers of validoxylamine A were synthesized by the condensation reaction of the blocked DL-validamine and the allyl bromide, the precursor of the unsaturated branched-chain cyclitol moiety.
- Ogawa, Seiichiro,Toyokuni, Tatsushi,Suami, Tetsuo
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p. 947 - 950
(2007/10/02)
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