Glucopyranosyl fluorides preparation

The Mukaiyama condensation method was also utilized in the synthesis of several antibiotics and related bioactive substances. These syntheses include apramycin, using 4-azido-2,3,6-tri-(P-benzyl-4-deoxy-) -D-glucopyranosyl fluoride (prepared from the corresponding a-D-glucopyranosyl chloride by the AgF method ) avermectin B , using protected sugar derivatives of oleandrosyl fluoride (a-L-Ole-F) and 0-(a-L-01e)-(1 4)-a-L-0le-F (both... 

Glycosylations utilizing the aforedescribed glycosyl fluorides are described next. In 1981, Mukaiyama and coworkers attempted to prepare 1,2-cw-glycosides by utilizing the relatively stable (as compared with other glycosyl halides) 2,3,4,6-tetra-0-benzyl-)8-D-glucopyranosyl fluoride (47)5)... 

Benzylidene acetals of the aldosyl fluorides can be prepared by treatment with benzaldehyde-zinc chloride, if two suitably situated hydroxyl groups are present in the sugar derivative. This method has afforded 4,6-0-benzylidene- 8-D-glucopyranosyl fluoride. 

To explore the dependence of the equilibrium on the nature of the anion, the fluoroborate salt of 59 was prepared. It was obtained at low temperature (0 ) either by the reaction of tetra-0-acetyl-/3-D-glu-copyranosyl fluoride (53) with boron trifluoride in carbon tetrachloride, or by treatment of tetra-O-acetyl-a-D-glucopyranosyl bromide (54) with silver fluoroborate in nitromethane. In edier, compound 54 and silver fluoroborate give a mixture of tetra-O-acetyl-a- and /3-D-glucopyranosyl fluoride, because the ether complexes with the boron trifluoride, and so a fluoroborate anion is no longer available. On dissolution of the fluoroborate salt of the D-gluco acetoxonium ion (59) in nitromethane or acetonitrile, an acyloxonium-ion rearrangement, is observed with consequent equilibration, between 59 60 61 62, that is not significantly different from... 

Based on prior experiences where immobilized cyclodextrin a 1-4 glucosyltransferase (iCGT) was prepared and used with a-D-glucopyranosyl fluoride (GF) as the donor (7), we have demonstrated the iCGT catalyzed incorporation of a-D-glucopyranosyl units (G) to polymer-bound maltodextrins (PBM the polymer being water-soluble substituted poly (acrylamide), 8). It has been predicted that using a soluble polymer... 

Bosso, C., J. Defaye, A. Domard, A. GadeUe, and C. Pedersen. 1986. The behaviour of chitin towards anhydrous hydrogen fluoride. Preparation of P-(l—>4)-linked 2-acetamido-2-deoxy-D-glucopyranosyl oligosaccharides. Carbohydr. Res. 156 57-68. 

Trideoxy-3,4,6-trifluoro- C-D-galactopyranosyl fluoride has been prepared from 3-deoxy-3-fluoro- c-D-glucopyranosyl fluoride using the diethylamino-sulphur trifluoride (DAST) procedure, and its stereochemistry determined by detailed multinuclear n.m.r. experiments. The DAST method has also been used to prepare 6,6 -dideoxy-6,6 -difluoro-sucrose from 2,3,4 3 4 -P nta-0-benzoyl-sucrose. The free 1 -hydroxy group was not substituted by fluorine. 

Glycosyl fluorides may be prepared by displacement of per-O-acyl or suitably protected 2-0-acyl 1-halides (Cl or Br) with fluoride [AgF (Refs. 28 and 29), KHF2 (Ref 30) or AgBF4 (Ref 31)]. -o-Glucopyranosyl [ F]fluo-... 

Glycosyl fluorides have also been prepared by treatment of per-O-acyl or partially 0-acylated sugars with hydrogen fluoride [liquid HF (for example, see Refs. 38 and 39) or HF in acetic acid or dichloromethane], as exemplified by 2,3,4-tri-O-benzyl-a-D-xylopyranosyl (18), a-D-glucopyranosyl (19), tetra-O-pivaloyl-a-D-glucopyranosyl (20), and 2,3,5-tri-O-acetyl-D-xylofur-anosyl fluorides (21) (see Table 1). Frequently, HF treatment - leads to... 

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