A-D-Fructose, 4-

Asymmetric epoxidation of disubstituted E-alkanes using a d-fructose... 

ASYMMETRIC EPOXIDATION OF DISUBSTITUTED E-ALKENES USING A d-FRUCTOSE BASED CATALYST121... 

By 1920, it was recognized that a successful chemical synthesis would probably require the use of a D-fructose maintained in the proper cyclic structure by the presence of substituents. The substituent groups would have to be stable enou to survive the conditions required in condensation with a suitable D-glucose derivative, but at the same time be capable of ready removal by agents that failed to affect any sucrose... 

Figure 4. Hydroxyl PMR signals (solvent, methyl sulfoxide-d6) for A) D-fructose after prior equilibration in water B) D-fructose at equilibrium in methyl sulfoxide-d6 C) leucrose, freshly dissolved crystals D) furanose, freslily dissolved crystals (arrows show the positions of signals that increase in intensity with time) G2-hydroxyl proton-2, F4-hydroxul proton-4 E) lactulose, freshly dissolved crystals. At the upper right are 13C-2 signals at 25.15 MHz for D-fructose in water (see Reference...

The lactone of a-d-fructose-carboxylic acid, M.P. 130°, is prepared in the same manner from d-fructose (lsevulose). It will be noted that from glucose, four carboxylic acids can be obtained—an a- and /3-acid from each of the optical isomers (A., 270, 64). Like many acids containing a y-hydroxy group, all these free acids are unstable, immediately forming lactones on liberation from their salts. 

Some monosaccharides may also be classified as being epimers. Epimers are compounds that have identical configurations except for one carbon atom. For example, a-D-glucose and a-D-fructose are epimers. Epimers sometimes react with the same reagent to form the same product. For example, both a-D-glucose and a-D-fructose react with phenylhydrazine to form the same osazone. 

In contrast man may have a B-D-fructopyranose site since this compound is believed to be the sweetest fructose isomer (2, 26). Further evidence for a D-fructose site in otEer animals completely distinct from a sucrose or a D-glucose site is evident in single fiber responses (27,28) or in biochemical studies (29). 

Reliable information relating to a ketose of formula I came first from the research of Ohle and Just.8 They prepared the first crystalline derivatives of D-psicose, namely l,2-isopropylidene-3,4-anhydro-D-psicose (V), and some of its esters by means of a Walden inversion in the detosyla-tion of 3-tosyl-l,2-isopropylidene- a -D-fructose (IV).12 Attempts to... 

Step 2 is the isomerization of a-D-glucose 6-phosphate, by glucose-6-phosphate isomerase, to a-D-fructose 6-phosphate. This is a freely reversible reaction. 

Step 3 is the phosphorylation of a-D-fructose 6-phosphate to a-D-fructose 1,6-bisphosphate. The enzyme is phosphofructokinase and ATP and Mg2+ are required. 

ASYMMETRIC EPOXIDATION OF trans-p-METHYLSTYRENE AND 1-PHENYLCYCLOHEXENE USING A D-FRUCTOSE-DERIVED KETONE (R,R)-trans-P-METHYLSTYRENE OXIDE AND (R,R)-l-PHENYLCYCLOHEXENE OXIDE... 

Fig. 1 Chemical structures of di-D-fructose dianhydrides (1-7 and 9-14) and of a D-fructose-D-glucose mixed dianhydride (8), with indication of the preferred conformation of six-membered rings...

The use of phenyl p-o-glucopyranoside as internal standard and authentic samples of DFAs obtained by synthesis allowed determination of the corresponding response factors for quantitative analysis. The relative abundance of DFA diaster-eomers in a D-fructose caramel obtained by heating a concentrated solution of sucrose in the presence of 10% citric acid was found to correspond to a kinetic distribution, the ot-D-fructofuranose p-o-fructofuranose l,2 2,l -dianhydride 10 being the major component in the mixture (Fig. 4). 

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