Tagatose, structure

Table sugar, sec Sucrose Tagatose, structure of, 975 Talose. configuration of, 982 Tamiflu, molecular model of, 130 Tamoxifen, synthesis of, 744 Till] DNA polymerase, PCR and, 1117 Tartaric acid, stereoisomers of, 305-306... 

The four kelohexoses are fructose, sorbose, allulose and tagatose. See glucose for example of isomerization between open chain and cyclic structures in a typical hexose molecule. 

From 3,6-Anhydromonosaccharide OsotriazdlesA —The osotriazoles of the 3,6-anhydro derivatives of D-psicose and L-tagatose gave the same dialdehyde monohydrate, to which the hemialdal structure (33) was assigned. The mirror-image product (34) was obtained from oxidation of the HC=N... 

Methylation of tagatose (using CH3I and Ag20) followed by acidic hydrolysis gives 1,3,4,5-tetra-O-methyltagatose. Draw a Fischer projection structure for the open-chain form of tagatose. 

In addition to fructose (Practice Problem 22.12) and sorbose (Problem 22.24), there are two other 2-ketohexoses,/> V< reand tagatose. D-Psicose yields the same phenylosazone as D-allose (or D-altrose) D-tagatose yields the same osazone as D-galactose (or D-talose). What are the structures of D-psicose and D-tagatose ... 

Ribofuranosyl derivatives of substituted benzimidazoles have been found to have virus inhibitory activity (44)-From glucosone, compounds with quinoxaline structures may be produced (4S), In the presence of hydrazine and o-phenylenediamine, 1-deoxy-1-p-toluino-D-fructose or -D-tagatose is converted to a quinoxaline compound in the pH range 6 to 8 by a mechanism similar to osazone formation 46),... 

To summarize the mechanistic and structural studies with hex-2-uloses and 2-C-(hydroxymethyl)pentoses performed under the conditions of the Bflik reaction, the following conclusion can be made. Molybdic acid catalyzes two types of interconversions between the sugars shown in Scheme 13. D-Fructose (17), d-sorbose (21) and D-tagatose (29) when treated with the catalyst are subjected to highly stereospecific carbon-skeleton rearrangements to produce thermodynamic equilibrium mixtures with the respective 2-C-(hydroxymethyl)-D-ribose (D-hamamelose, 20), 2-C-(hydroxymethyl)-D-lyxose (30), and 2-C-(hydroxymethyl)-D-xylose (31). (For simplicity, all the sugars are represented in their acyclic non-hydrated forms in spite of which some of their interconversions proceed in the acyclic hydrated structures, while others proceed in cyclic hemiacetal ones. All of the interconversion relationships are schematically represented in the d series, despite the fact that some of them were experimentally performed with the L series.) Probably because of extensive formation of unproductive com-... 

The separation on several columns of the isomeric forms of several aldohexoses and the four ketohexoses (fructose, psicose, sorbose and tagatose) as their pertrimethylsilyl ether derivatives has been reported, and a mathematic approach used in an attempt to relate retention times to structures. 

Structural details are also available for the class II (/ia)8-barrel enzyme FruA from E. coli at excellent resolution (1.6A) [51, 52]. The homodimeric protein requires movement of the divalent zinc cofactor from a buried position to the catalytically effective surface position. Recent attempts to explore the origin of substrate discrimination of the structurally related E. coli aldolase vith specificity for tagatose 1,6-bisphosphate by site-directed mutagenesis and structure determinations highlight the complexity of enzyme catalysis in this class of enzymes and the subtleties in substrate control [53-55]. 

Reduction of D-tagatose with sodium borohydride yields a mixture of galactitol and talitol. What is the structure of D-tagatose ... 

Hall, D. R., Bond, C. S., Leonard, G. A., Watt, I., Berry, A., and Himter, W. N., Structure of tagatose-l,6-bisphosphate aldolase— Insight into chiral discrimination, mechanism, and specificity of class II aldolases. /. Biol. Chem. 2002, 277 (24), 22018-22024. 

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