D-glucopyranosyl chloride

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... 

Similarly, Shen and coworkers36 obtained 4-0-(2-acetamido-3,4,6-tri-O- acetyl - 2 - deoxy -/ - d- glucopyranosyl) -N- (benzyloxycarbonyl)homo-serinamide (164) by coupling 2-acetamido-3,4,6-tri-0-acetyl-2-deoxy-a-D-glucopyranosyl chloride (6) with 2-N-(benzyloxycarbonylamino)-4-hydroxybutanamide128 (163) in the presence of mercury dicyanide. 

Ci4H1gC109 Tetra-O-acetyl-a-D-glucopyranosyl chloride ACGLUP 31 368... 

Because of the particular structural features of compound 4, pointed out in Section I, the D-glucofuranosyluronic halide anomers not only have inverse thermodynamic stabilities with respect to those of D-glucopyranosyl halides but also show a different behavior towards alcohols. For instance, 2,5-di-O-acyl-a-D-gluco-furanosylurono-6,3-lactone halides, which are difficult to prepare, do not react with alcohols, inasmuch as an endo approach of the reagent is inhibited.14 The /3-bromides and -chlorides, however, just like /3-D-glucopyranosyl chlorides, are subject to alcoholysis, with formation of /3-D-glucofuranosidurono-6,3-lactones.16... 

C-Glucosidation. Reaction of the protected a-D-glucopyranosyl chloride 1 with silyl enol ethers activated with AgOTf results in a-C-glucosyl esters or ketones. 

Glycosidation (13,302). Glycosidation of 2-acetamido-3,4,6-triacetyl-2-deoxy-a-D-glucopyranosyl chloride (1) mediated by Sn(OTf)2 provides exclusively P-glycosides. The most satisfactory base is 1,1,3,3-tetramethylurea, and CH2CI2 is the preferred solvent.2... 

A much more systematic approach involves the use of p-chlorides carrying non-participating groups at C-2 as is exemplified by the Wolfrom synthesis of p-isomaltose octa-acetate from 1,2,3,4-tetra-O-acetyl-p-D-glucopyranose and 3,4,6-tri-0-acetyl-2-0-nitro-p-D-glucopyranosyl chloride In this work silver carbonate was used as acid acceptor and soluble silver perchlorate was fmmd to exert valuable catalytic influence, but later the perchlorate itself was used in an application to a tiisacchar-ide s mthesis which incorporated the trityl ether modification 2 ). 

The first synthesis of octa-0-acetyl-/3-maltose was reported by Le-mieux10 in 1953. When 1,2,3,6-tetra-0-acetyl-/3-D-glucopyranose was heated with 3,4,6-tri-0-acetyl-l,2-anhydro-a-D-glucopyranose for 13 h at 100°, it gave a mixture from which the product was isolated, after acetylation, in 8.7% yield. Octa-0-acetyl-/3-maltose has been obtained in 43.6% yield by way of condensation of 3,4,6-tri-0-acetyl-2-0-ben-zyl-/3-D-glucopyranosyl chloride with l,2,3,6-tetra-0-acetyl-/3-D-gluco-pyranose.11... 

The product is scraped from the walls of the flask and broken up by means of a curved spatula. The solid is collected on a 12.5-cm. Buchner funnel, washed with two 150-ml. portions of dry ether, dried by suction on the filter for 5 minutes, and stored in a desiccator over sodium hydroxide and phosphorus pentoxide. Analytically pure 2-acetamido-3,4,6-tri-0-acetyl-2-deoxy-a-D-glucopyranosyl chloride is obtained weight 55-65 g. (67-79%) m.p. 127-128° (Fisher-Johns apparatus) (Note 7) typical — NHCOCH3 absorptions at 6.09 n and 6.49 n in the infrared. Evaporation of the mother liquors and addition of ether to the concentrated solution gives an additional 4-6 g. (5-7%) of crystalline product, m.p. 125-127°, that is sufficiently pure for most purposes. The pure product may be stored in an open dish in a desiccator at room temperature for at least 3 years without decomposition (Note 8). 

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