Showing papers on "Aldose published in 1991"

Stereochemical studies of the beta-elimination reactions at aldehydic abasic sites in DNA: endonuclease III from Escherichia coli, sodium hydroxide, and Lys-Trp-Lys.

Abstract: The DNA strand cleavage reaction catalyzed by endonuclease III from Escherichia coli (endo III) on the 3'-side of aldehyde abasic sites proceeds by a syn beta-elimination involving abstraction of the 2'-pro-S proton and formation of a trans alpha,beta-unsaturated aldose product; we previously reported the same stereochemical course for the reaction catalyzed by UV endonuclease V from bacteriophage T4 (UV endo V) [Mazumder, A., Gerlt, J. A., Rabow, L., Absalon, M. J., Stubbe, J., & Bolton, P. H. (1989) J. Am. Chem. Soc. 111, 8029-8030]. Since the UV endo V does not contain an 4Fe-4S center, the 4Fe-4S center present in endo III need not be assigned a unique role in the beta-elimination reaction. The beta-elimination reactions that occur under alkaline conditions (0.1 N NaOH) and in the presence of the tripeptide Lys-Trp-Lys proceed by anti beta-elimination mechanisms involving abstraction of the 2'-pro-R proton and formation of a trans alpha,beta-unsaturated aldose product. The different stereochemical outcomes of the enzymatic and nonenzymatic beta-elimination reactions support the hypothesis that the enzyme-catalyzed reactions may involve general-base-catalyzed abstraction of the 2'-pro-S proton by the internucleotidic phosphodiester leaving group.

A stereochemically general synthesis of 2-deoxyhexoses via the asymmetric allylboration of 2,3-epoxy aldehydes

Abstract: Asymmetric allylborations of epoxy aldehydes using tartrate allylboronates (R,R)- and (S,S)- and applications of this chemistry to the highly diastereoselective synthesis of the four hept-1-ene-4,5,6,7-tetrol stereoisomers. The conversion of the arabino and lyxo diastereomers to 2-deoxy-glucose and 2-deoxygalactose, respectively, is also described

Ascent of the aldose series by four carbon atoms : total synthesis of d-glycero-d-talo-l-talo-undecose pentaacetonide

Abstract: Enantiomerically pure undecose acetonide 9 was synthetized, through heptose intermediate 5, starting with D-glyceraldehyde acetonide (1). The key steps were two consecutive four-carbon homologations, each consisting of four reactions: (i) stereoselective elongation of the aldehyde precursor with 2-(trimethylsiloxy)furan, giving C n+4 butenolide templates, (ii) anti-selective cis-dihydroxylation of the butenolide double bond, giving fully functionalized lactones, (iii) lactone ring opening and protection, giving open-chain methyl esters and (iv) DIBAL reduction to aldoses 5 and 9

A new synthesis of (2S,3R,4R)-2-(hydroxymethyl)pyrrolidine-3,4-diol

Abstract: The title compound 6 was synthesized from 2,3,5-tri-O-benzyl-D-arabinofuranose (7) in three steps and 48% overall yield. Moreover, it was shown, in the case of γ-hydroxy amide 9, that the Mitsunobu react-ion is not suitable for the preparation of γ-lactams, because O-alkylation is predominant

n-Pentenyl esters versus n-pentenyl glycosides. Synthesis and reactivity in glycosidation reactions

Abstract: n-Pentenyl esters, which are readily obtained by mild esterification of the anomeric hydroxy group of sugars, can be efficiently used in glycosidation reactions, and they appear to be less prone to armed–disarmed phenomena than their n-pentenyl glycoside counterparts.

Kinetic studies of Mg(2+)-, Co(2+)- and Mn(2+)-activated D-xylose isomerases.

Abstract: The kinetic parameters for the interconverting substrates D-xylose in equilibrium D-xylulose and D-glucose in equilibrium D-fructose were determined for several D-xylose isomerases, with Mg2+, Co2+ and Mn2+ as metal ion activators. The Km, kcat. and kcat./Km values are tabulated for the anomeric mixtures (observed parameters) as well as for the respective reactive species, i.e. the alpha-pyranose anomers of D-xylose and D-glucose and the alpha-furanose forms of D-xylulose and D-fructose (real parameters). The real Km values and catalytic efficiencies are more favourable for the ketose sugars (reverse reaction) than for the aldose sugars (forward reaction). Comparisons of the kinetic parameters further support the existence of two distinct groups of D-xylose isomerases. Inhibition constants for the cyclic substrate analogues 5-thio-alpha-D-xylopyranose and alpha-D-xylopyranosyl fluoride and for the acyclic substrate analogue xylitol and its dehydrated form 1,5-anhydroxylitol were determined and are discussed.

O-Alkyl-D-glucopyranosylamines and Their Derivatives.

Abstract: O-Alkyl-n-glucopyranosylamines are prepared by alkylation of glucose and subsequent exchange of the 1-hydroxy group by an amino group. The title compounds are being tested as chiral templates, in particular for peptide syntheses by asymmetric four-component condensations

Stereoselective Synthesis of 1,2- trans -Ribofuranosides from 1-Hydroxy Sugars by the Use of [1,2-Benzenediolato(2−)- O , O ′]oxotitanium and Trifluoromethanesulfonic Anhydride

Abstract: A convenient method for stereoselective synthesis of 1,2-trans-ribofuranosides directly from 1-hydroxy sugars and alcohols or trimethylsilylated nucleophiles by the use of [1,2-benzenediolato(2−)-O,O′]oxotitanium and trifluoromethanesulfonic anhydride is described.

Resolving isoforms of aldose reductase by preparative isoelectric focusing in the Rotofor.

Abstract: We have resolved and characterized isoforms of aldose reductase from bovine and porcine lenses by preparative isoelectric focusing with narrow pH gradients using the Rotofor. Both bovine and porcine lens aldose reductases were resolved as two enzyme isoforms. The bovine isoforms were Mr40400 +/- 445 polypeptides of pI4.71 and 5.19. Porcine isoforms were Mr41500 +/- 450 polypeptides of pI 4.90 and 5.30. Staphylococcus aureus V-8 protease digestion patterns for each set of isoforms were essentially identical and all isoforms probably contain blocked amino terminal amino acids. Antiserum to bovine lens aldose reductase cross-reacted with porcine lens aldose reductase. Each isoform displayed substrate preferences characteristic of mammalian aldose reductases. With purification, both bovine and porcine lens aldose reductases became less sensitive to inhibition by 6-fluoro-spiro-(chroman-4.4'-imidazolidine)-2',5'-dione (sorbinil).