O-Glucosylation

Various strains of oral streptococci produce D-glucosyltransferases which utilize sucrose as a o-glucosyl donor in the production of soluble and insoluble D-glucans. Consequently, it may be expected that some deoxyfluoro derivatives of sucrose function as competitive inhibitors for the dextransu-crases of tooth bacteria, thus preventing decay, or at least may be used as active-site probes for the enzymes. Another aim of these researches is to find non-metabolizable sweeteners. 

Deoxyfluorostarches were prepared from com starch by treatment of the tosylated (mostly at 0-6 of the o-glucosyl residues) starch precursors with KF in ethylene glycol (190°, 15 min) or by treatment of starch with hydrofluoric acid (Mc2SO, —30°, 4 h — room temp., 10 min). 

Y.-i. Matsushita, K. Sugamoto, Y. Kita, and T. Matsui, Silica gel-catalyzed jS-O-glucosylation of alcohols with l,2-anhydro-3,4,6-tri-0-pivaloyl-oc-d-glucopyra-nose, Tetrahedron Lett., 38 (1997) 8709-8712. 

To our knowledge, only one attempt has been made toward the preparation and use of a fixed glucosyl trichloroacetimidate.9 Takahashi et al. described the synthesis of an attached O-glucosyl trichloroacetimidate and extended the use of the well known traceless silyl linker strategy (Scheme 4.11). 

This enzyme [EC 5.1.3.11] catalyzes the interconversion of cellobiose to o-glucosyl-o-mannose. 

Figure 1. Postulated pathway for the enzymatic synthesis of polymethylated flavonol glucosides in Chrysosplenium americanum GT, O-glucosyl-transferase OH, hydroxylase OMT, O-methyl transferase.

Kaempferol-3-0-glucosyl(l-3)rhamnosyl (l-6)galactoside LP° Kaempferol-3-O-glucosyl-rhamnoside ... 

We therefore needed a ready synthesis of the 1,6-epithio epoxide 119. Normally, for such syntheses, the sulftir atom is introduced at an early stage [64]. However, it appeared to us that a suitable doubly-activated sugar such as 120 should be capable of direct conversion to the 1,6-epithio sugar 121 by treatment with some type of sulfur reagent. Indeed, the o-glucosyl bromide 122 was easily prepared and, upon treatment with either hydrogen sulfide and triethylamine in DMF or benzyltriethylammonium tetrathiomolybdate in chloroform, gave the... 

O- -glucosyl-D-glucose + Pi a-D-glucose 1-phosphate + D-glucose. (cellobiose)... 

The results of a detailed study of D-fructose and five O-glucosyl-substi-tuted D-fructoses17 confirmed that increasing the temperature increases the proportion of the furanose forms. This effect is much more noticeable in water and in pyridine than in dimethyl sulfoxide. In other ketoses, the proportion of the keto form also increases with increasing temperature.12... 

Furoquinoline Alkaloids.—Glycohaplopine (1 R1 = H, R2 = O-glucosyl, R3 = OMe), a new alkaloid isolated from Haplophyllum perforatum, is believed to contain a /3-glycosidic link.6... 

Composition of Products from Reaction of Tetra-O-acetyl-a-o-glucosyl Bromide with Methanol in the Presence of Silver Carbonate10... 

---