Glucopyranose deacetylation

Chitin and the deacetylated form, chitosan, are attractive linear amino polysaccharides found in the shell of crustaceans. These abundant biopolymers, composed mainly of poly(/T(l,4)-2-acetamido/2-amino-2-deoxy-D-glucopyranose)... 

Enzymic hydrolysis can often provide the means for solving a problem involving the partial hydrolysis of esters. A synthesis145 of 1-O-ab-scisoyl-/3-D-glucopyranose proved difficult at the last step, but the use of a crude enzyme-preparation obtained from ripe seeds of Helianthus annus allowed deacetylation to be achieved at 0-2, 3, 4, and 6 of the D-glucosyl group without rupture of the ester bond to the anomeric center. 

Mercaptolysis of /3-D-glucopyranose pentaacetate in ethyl mercaptan at 0°, with zinc chloride as catalyst, gives ethyl tetra-O-acetyl-l-deoxy-1-thio-/S-D-glucopyranoside in 71% yield. Under the same conditions, a-D-glucopyranose pentaacetate reacted only very slowly, but it could be shown that the deoxy-thio-/3-D-glucoside is formed in much greater amount than is the a anomer. Mercaptolysis of the D-mannopyranose pentaacetates under the same conditions for 48 hours resulted in a 70% yield of ethyl tetra-O-acetyl-l-deoxy-l-thio-a-D-mannopyranoside from the /3-D-pentaacetate, and in a 60% yield from the a anomer.103 Inspection, by preparative paper chromatography, of the residual sirups, after deacetylation, led in each case to the isolation of the anomeric ethyl-1-... 

With the other types of neutral dithiocarbonate (X—S—CO—SR and X—S—CS—OR), where the carbohydrate residue is esterified through sulfur instead of oxygen, alkaline hydrolysis yields the salt of a thiol (X— SH). In the cases of 1,2 5,6-di-0-isopropylidene-3-/S -[(methylthio)thio-carbonyl]-3-thio-D-glucofuranose (LXVI) and 2,3,4,6-tetra-0-acetyl-l-(S-(ethoxythiocarbonyl)-l-thio-/9-D-glucopyranose (LXXXI) this change was brought about very readily with methanolic ammonia, being accompanied in the latter instance by deacetylation. Sodium and potassiiun alkoxides have also been used. ... 

The most important derivative of chitin is chitosan obtained by partial deacetylation of chitin in the solid state under alkaline conditions or by enzymatic hydrolysis in the presence of a chitin deacetylase. The ratio of 2-acetamido-2-deoxy-D-glucopyranose to 2-amino-2-deoxy-D-glucopyra-nose moieties determines the identity of the product, that is, chitin or chitosan [9]. The published methods used for the production of chitosan from chitin are summarized in Table 2.3. 

When a- or 8-D-glucopyranose pentaacetate is treated with piperidine (three molecular proportions are best), deacetylation occurs on Cl and C2, and the product is iV -(3,4,6-tri-0-acetyl-D-glucosyl)piperidine, whose structure was proved by conventional methods, including its conversion into 2-0-methyl-D-glucose. The same triacetate is obtained when piperidine reacts with 3,4,6-tri-O-acetyl-D-glucosyl chloride or with D-glucose 2,3,4,6-tetraacetate. Loss of the acetyl group on C2 must accompany or... 

The synthesis of cellobiose octaacetate by the reaction of the sodium derivative of 1,2,3,6-tetraacetyl-D-glucopyranose with 2,3,4,6-tetraacetyl-a-D-glucopyranosyl bromide has recently been reported. Deacetylation resulted in the formation of cellobiose. 

Chitosan is a second abundant heteropolysaccharide composed of /3-[l-4]-2-deoxy-2-amino and -2-acetamino D-glucopyranose units [31]. Chitosan is the partial deacetylated (involving alkaline hydrolysis] product of chitin. Chltln is the main component of outer skeleton of small insects, cuticles, and the shells of shrimp, crab, lobster, etc. Chitosan has been expansively investigated in the pharmaceutical industries for the development of various sustained and controlled release drug delivery systems due to its versatile biological activity [as food and non-food items] and excellent biocompatibility. Hirano [22] conducted an experiment with both healthy and infected skin and found the LD50 in case of orally administered mouse to be [>16 g/kg]. Wu et al. [76] worked on... 

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