A 2,3,4,6-tetra-O-acetyl

An acylated glycosyl halide, such as a 2,3,4,6-tetra-O-acetyl derivative, is treated with thiourea. The resulting pseudothiouronium salt is hydrolyzed with aqueous potassium carbonate to give the 2,3,4,6-tetra-0-acetyl-l-thio-(3-D-glucopyranose,48 which then is alkylated. 

A. 2,3,4,6-Tetra-O-acetyl-T)-gluconic acid monohydrate. Crushed, fused zinc chloride (20 g.) is shaken with 250 ml. of acetic anhydride in a 1-1. three-necked flask until most of the solid... 

The compound of Micheel and Micheel was obtained in small amount after treatment of 2,3,4,6-tetra-O-acetyl-a-D-mannosyl bromide with tri-methylamine the bulk of the material remained unchanged. The product apparently resulted from hydrolysis by moisture from the air. The composition was established by analyses, but the identification was reported with a question mark. A 2,3,4,6-tetra-O-acetyl-D-mannose with different physical constants (m.p. 93°, [c ]d +26.3°) was obtained by Levene and Tipson63b by the deliberate addition of water and silver carbonate to tetra-O-acetyl-D-mannopyranosyl bromide its structure was confirmed by conversion to the known pentaacetates. If Micheel and Micheel were correct in their identification, the two acetates could be anomers. The acetylation and deacetylation reactions performed by Maurer and Bohme are additional evidence in favor of this relationship. 

Key A = 2,3,4,6-tetra-O-acetyl- -D-glucose B = 2,3,4,6-tetra-O-acetyl-a-D-glucosyl bromide. 

The carbohydrate 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide reacts with NaCo(CO)4 and PPh3 under 10 atm of CO to yield the expected acetyl (XXIX) and the corresponding alkyl 210). The former decarbonylates readily on storage or chromatography. Retention of configuration at carbon accompanies CO elimination. 

On treatment of trialkylsilyl nitronates 1043 with MeLi, LiBr, or BuLi in THF the resulting nitrile oxide intermediates 1044 afford, in dilute THF solution (R=Me) the ketoximes 1045 in ca 50-60% yield, whereas in concentrated THF solution the O-silylated hydroxamic acids 1046 are obtained as major products [144] (Scheme 7.35). Analogously, the silyl nitronate 1047 reacts with the 2,3,4,6-tetra-O-acetyl-/ -D-glucopyranosyl thiol/triethylamine mixture to afford, via the thiohydroxi-mate 1048, in high yield, a mixture of oximes 1049 which are intermediates in the synthesis of glucosinolate [145] (Scheme 7.35). 

Razi, M.T, Sadler, P.J., Hill, D.T. and Sutton, B.M. (1983) Proton, carbon-13, and phosphoms-31 nudear magnetic resonance studies of (2,3,4,6-tetra-O-acetyl-l-thio-p -n-glucopyranosato-S) (triethylphosphine)gold (auranofin), a novel antiarthritic agent Journal of the Chemical Society, Dalton Transactions, (7), 1331-1334. 

Treatment of the disaccharide derivative, 2,3,6-tri-0-acetyl-4-0-(2,3,4,6-tetra-O - acetyl -fi-D- galactopyranosyl) -fi-D- glucopyranosyl-amine (46), with 71 also gave50 a mixture of protected L-aspart-1- and -4-oyl disaccharide derivatives (77 and 78). The almost identical yields of... 

The Helferich-Wedemeyer procedure may give mixtures of the anomers, depending on the nature of the aglycon. For example, condensation of bromide 128 with N-(benzyloxycarbonyl)-L-threonine penta-chlorophenyl ester (171) gave both N-(benzyloxycarbonyl)-3-0-(2,3,4,6-tetra-O-acetyl-a- and -/J-D-glucopyranosyl)-L-threonine pen-tachlorophenyl ester135 (172 and 173, respectively), but only the fi-D... 

The living character of the ROMP promoted by the initiator Ru(CHPh)(Cl)2 (PCy3)2 (Cy = cyclohexane) was tested with the synthesis of diblock, triblock, and tetrablock copolymers of norbornene derivatives carrying acetyl-protected glucose, [2,3,4,6-tetra-O-acetyl-glucos-l-O-yl 5-norbornene-2-carboxylate], A or maltose groups, [2,3,6,2/,3/,4/,6/-hepta-0-acetyl-maltos-1-O-yl 5-norbornene-2-carboxylate], B, shown in Scheme 41 [102]. The AB, ABA, and ABAB structures were prepared by sequential addition of monomers with narrow molecular weight distributions to quantitative conversions. 

Similarly, treatment of the salt with 2,3,4,6-tetra-O-acetyl-a-D-glucopyra-nosyl bromide 46 gave 4-[2,3,4,6-tetra-0-acetyl-/3-D-glucopyranosyl]-4//-pyrido[2,3-e][l,2,4]triazin-3-one 1-oxide 47. Antileukemia tests for the 4-alkyl derivatives showed no activity. 

Compound 33 also lends itself to the synthesis of 1,5-linked disaccharides. Thus, its condensation180 with 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide, and with methyl 2,3,4-tri-O-acetyl-a-D-glucopyranosyluronate bromide, respectively, yields the corresponding /3-D-linked disaccharides (97 and 98). 

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