D-glucosyl fluoride

S. Kitahata, C. F. Brewer, D. S. Genghof, T. Sawai, and E. J. Hehre, Scope and mechanism of carbohydrase action. Stereocomplementary hydrolytic and glu-cosyl-transferring actions of glucoamylase and glucodextranase with alpha- and beta-D-glucosyl fluoride, J. Biol. Chem., 256 (1981) 6017-6026. 

A small piece of Na was added to MeOH (5 mL) and the resulting solution was added to tetra-O-acetyl-a-D-glucopyranosyl fluoride (130 mg, 0.37 mmol) and 4,6-di-6>-acetyl-2-deoxy-2-fluoro-3-0-(tetra-6>-acetyl-/3-D-glucopyranosyl)-/ -D-glucosyl fluoride (44 mg, 0.07 mmol) in MeOH (5 mL) and the solution stirred (1 h) before being neutralized with Amberlite resin IR-120 (H+), fdtered and concentrated to afford a colourless residue. 

Table I (104) shows the yields of products from maltose to malto-pentaose recovered from digests of 0.2 M crystalline a-D-glucosyl fluoride with crystalline a-amylase preparations from six different biological sources. The digests were incubated at 30 °C for 10 minutes, heat inactivated, and chromatographed for product isolation and analysis.

Table I. Maltosaccharide Synthesis from a-D-Glucosyl Fluoride...

Table II (104) shows the results of an experiment to learn the proportion of a-D-glucosyl fluoride that is hydrolyzed vs. that used for saccharide synthesis by the different crystalline a-amylases and by diluted saliva. The substrate was again 0.2 M and the enzymes at one-tenth to one-one hundredth the concentrations of the preceding experiment. These digests were analyzed directly for amounts of fluoride (104, 107) and D-glucose (glucose oxidase method) liberated during 2 hours at 30°C.

All the amylases caused release of more fluoride than D-glucose, both expressed as percent of substrate. The difference between them gives the percent substrate converted to saccharides. The main point is that with six of the seven a-amylases two to twenty times more a-D-glucosyl fluoride was converted to oligosaccharides than hydrolyzed to D-glucose. The great discrepancy was readily confirmed by direct visualization of the products by chromatography. In this experiment, preparations of so-... 

Table II. Saccharide Synthesis vs. a-D-Glucosyl Fluoride Hydrolysis by Different a-Amylases °...

The most important features are, first, that some of the a-amylases— i.e., those in digests Numbers 4, 5, 6, and 7 have catalyzed glycosylations from a-maltosyl fluoride at one-tenth to one-one hundredth the enzyme concentrations required for action on a-D-glucosyl fluoride. The Aspergillus oryzae a-amylase, which had the weakest synthetic action on a-D-glucosyl fluoride of the enzymes tested at 100 ftg/ml, has produced under conditions of this experiment an extended series of maltosaccharides at 1 fig/ml. 

D-Glucosyl fluoride (500 mg.) and an equivalent amount of glycine in water (25 ml.) containing sodium bicarbonate was kept at room temperature for 1 day, and then for 3 days at 36-39°, at pH 7-8. The solution was now evaporated to dryness under diminished pressure, and a methanol extract was made. Addition of absolute ether precipitated the product (180 mg., 25% yield) as a colorless, amorphous material, [< ] +15.4° (in water). 

The fluoride LXXI is unaffected by aqueous solvents, and it undergoes alkaline hydrolysis, with difficulty, to give 2-acetamido-2-deoxy-D-glucose. 3,4,6-Tri-0-acetyl-2-deoxy-2 - (p - tolylsulfonamido)-a - d - glucosyl fluoride... 

Triacetyl derivative of 6-tripbenylmethyl-glucoeyl fluoride Tetrabenzoyl-d-glucosyl fluoride... 

Properties of Some 2-Amino-2-deoxy-D-glucosyl Fluorides... 

Cf8C02C4H9 (CHF2CH2)3P04 cf-GIucosyl fluoride-6-chlorhydrin CHCI2GF2OC4H9-S6C d-Glucosyl fluoride... 

The first-order rate constants for the solvolyses of a-D-glucosyl fluoride in H2O-MeOH at 30° C are shown in Table 9. ... 

The Swain-Scott dependence for the reaction of nucleophiles with a-D-glucosyl fluoride is ... 

Sucrose phosphorylase catalyzes reversible glucosyl transfer from sucrose to orthophosphate, although other acceptors, including As04 ", water, fructose, and a number of other ketoses, are equally suitable. Donor specificity is more strict and, aside from the substrate/product pair of sucrose and a-D-glucosyl phosphate, only a-D-glucosyl fluoride has been well characterized (12, 148-151). 

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