D-fructose from

It has been mentioned that the mixture of trimethyl-D-fructoses from the acid hydrolysis of hexamethyl-di-D-fructose anhydride III, which are now known to be the 3,4,6- and 1,4,6-trimethyl-D-fructoses, shows a specific rotation near that of pure 3,4,6-trimethyl-D-fructose it is to be inferred accordingly that these two trimethyl-D-fructoses do not differ greatly in rotation. Montgomery76 has synthesized 1,4,6-tri-methyl-D-fructose and found its rotation in chloroform to be [a] d = + 29.7°, a value approximating that of 3,4,6-trimethyl-D-fructose (+ 27.7° in the same solvent). Pertinent also are the respective rotations of the acetone condensation products from these two trimethyl-D-fructoses. Montgomery found that 3,4,6-trimethyl-D-fructose under-... 

A compound represented by XVIII would yield 1,3,4-trimethyI-D-fructose, a crystalline substance with [aJD20 = — 51.4° (water), and 1,3,6-trimethyl-D-fructose (now unknown), upon hydrolysis of its hexa-methyl derivative. No evidence has been obtained to indicate the presence of this negatively rotating trimethyl-D-fructose and it is established that the mixture of trimethyl-D-fructoses from hexamethyl-di-D-fructose anhydride II rotates in the positive range of 25 to 30°. Unless the 1,3,6-trimethyl-D-fructose should prove to possess the unusually high rotation of about + 100°, which seems at least improbable, structure XVIII can be excluded. 

Batch crystallization studies of D-fructose from aqueous ethanolic solutions demonstrate that crystal growth rate is dependent on supersaturation (possibly to the 1.25 power), ethanol content and temperature. It appears that solution viscosity also has an effect. Growth rates of up to 1 pm/mln were measured. 

The 3700-2700-cm-1 region is less easy to interpret than the region below 1700 cm-1. Nevertheless, comparative study of intensities of the C-H vibrations permitted differentiation of D-fructose from D-glucose and sucrose. It was found187 that the asymmetrical vibration pas(C-H) for CH2 in d-fructose is stronger than the symmetrical vibration the opposite was observed for D-glucose, and the spectrum of sucrose exhibits almost the same intensity for the two vibrations. This result (see Fig. 19), which could... 

A higher space-time yield (98 versus 59 g 1, 1 d ) was reached in an EMR than in a batch reactor for the synthesis of dTDP-glucose and by-product D-fructose from sucrose and dTDP (Elling, 1995). 

S. Yu, K. Bojsen, B. Svensson, and J. Marcussen, a-l,4-Glucan lyases producing 1,5-anhydro-D-fructose from starch and glycogen have sequence similarity to a-glucosidases, BBA Protein Struct. Mol. Enzym., 1433 (1999) 1-15, review, 53 references. 

Figure 7.20 Mechanism for the formation of 1,5-anhydro-D-fructose from starch by the exo-acting starch lyase.

Methyl 7 -D-fructoside was first made when Menzies89 dissolved D-fructose in methanolic hydrogen chloride and stopped the reaction when the [a]D reached a maximum (after about 30 minutes). The sirup obtained on removal of the methanol by distillation was partially soluble in ethyl acetate, leaving a residue with negative specific rotation, which was probably methyl D-fructopyranoside and unchanged D-fructose. From the ethyl acetate solution sirupy methyl 7 -D-fructoside, [c ]d +26.6° in water, was obtained. Schlubach and Rauchalles90 showed that this fructoside was only partially hydrolyzed by invertase. This enzymatic hydrolysis was further investigated by Purves and Hud-... 

Four trimethyl-D-fructoses are known but only one of them is crystalline. Crystalline 1,3,4-trimethyl-D-fructose has been obtained from methylated levan,10 1,4,6-trimethyl-D-fructose from methylated melezi-tose and by synthesis, 3,4,6-trimethyl-D-fructose from methylated inulin and by synthesis, and 3,4,6-trimethyl-D-fructose has been synthesized. 

The only dimethyl-D-fructose which has been characterized, 3,4-di-methyl-D-fructose, has been prepared by McDonald and Jackson141 from di-D-fructose anhydride I. Tritylation of this anhydride gives the 6,6 -ditrityl derivative which is methylated to 3,4,3, 4 -tetramethyl-6,6 -di-trityl-di-D-fructose anhydride I. Removal of the trityl groups followed by hydrolysis yields liquid 3,4-dimethyl-D-fructose, [ ]d —60.66° in water. It has also been obtained, with 4-methyl-D-fructose, from the hydrolysis of methylated di-D-fructose anhydride III. The structure of this dimethyl-D-fructose follows from its method of preparation from di-D-fructose anhydride I whose structure is known.10 McDonald and Jackson also prepared 3,4-dimethyl-D-fructose from inulin by the following method inulin — monotrityl inulin — monotrityl inulin diacetate — dimethyl monotrityl inulin — dimethyl isopropylidene-D-fructose — methyl dimethyl-D-fructoside —> 3,4-dimethyl-D-fructose. Its structure was confirmed by its oxidation without loss of methyl to the same lactol of the dimethyl dibasic acid obtained from 1,3,4-trimethyl-D-fructose (see page 78). The phenylosazone made from 3,4-dimethyl-D-fructose has m. p. 126° that from 3,4-dimethyl-D-glucose has not been recorded. 

Ohle118 obtained 1-methyl-D-fructose by methylating 2,3 4,5-diiso-propylidene-D-fructopyranose and then hydrolyzing the resulting crystalline 1-methyl derivative. Brigl and Widmaier m have prepared 1-methyl-D-fructose from dibenzylidene-D-fructose. An alternative method is described by Brauns and Frush142 who hydrolyzed crystalline 1-methyl-D-fructosyl fluoride 3,4,5-triacetate, obtained by methylation with methyl iodide-silver oxide of crystalline D-fructosyl fluoride 3,4,5-triacetate, which results from the action of anhydrous hydrogen fluoride on D-fructose 1,3,4,5-tetraacetate. 

Tetramethyl-D-fructose from methylated asparagosin Dimethyl-D-fructose from methylated liquid +21.1°— +15.3 CHCls 184... 

Dimethyl-D-fructose from methylated asphodelin Dimethyl-D-fructose (A) from liquid + 19.6 CHCIj 185... 

Dimethyl-D-fructose from methylated irisin Dimethyl-D-fructose from dimethyl liquid +20.0 CHCls 191... 

Although TA from yeast is commercially available, it has rarely been used in organic synthesis applications, and no detailed study of substrate specificity has yet been performed. This is presumably due to high enzyme cost and also since the reaction equilibrium is near unity, resulting in the formation of a 50 50 mixture of products. In addition the stereochemistry accessible by TA catalysis matches that of FruA DHAP-dependent aldolase and the latter is a more convenient system to work with. In one application, TA was used in the synthesis D-fructose from starch.113 The aldol moiety was transferred from Fru 6-P to D-glyceraldehyde in the final step of this multi-enzyme synthesis of D-fructose (Scheme 5.60). This process was developed because the authors could not identify a phosphatase that was specific for fructose 6-phosphate and TA offered an elegant method to bypass the need for phosphatase treatment. 

Scheme 5.60. Transaldolase catalyzed synthesis of D-fructose from starch. P = PO32. ...

As a typical acetal bond, a glycosidic bond readily hydrolyzes in an acid-catalyzed reaction. In this manner, di- and oligosaccharides can be split into monosaccharides. It is a common method for manufacturing of invert sugar, a mixture of a-D-glucose and P-D-fructose, from sucrose. 

Whether these alkaline-earth metal ions are capable of directing the course of the transformation is at present unclear. Kusin reported that, when D-glucose reacts in calcium hydroxide solution at 25°, no D-fructose appears, whereas sodium hydroxide brings about formation of D-fructose under the same conditions of time and temperature. However, this claim is contrary to the findings of Lobry de Bruyn and Alberda van Ekenstein, Sowden and Schaffer, and Topper and Stetten, all of whom isolated D-fructose from the reaction of D-glucose with calcium hydroxide under comparable conditions. 

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