Acetals maltose derivatives

The re osdective sul tion of several mono- and di-saccharide derivatives via dibutylstannylene acetals has been investigated methyl 4,6-0-bem dene-a-D-gluco- and -galacto-pyranoside were sulfated at 0-2 in 84 and 79% yield, respectively, and />-methoxyben I 6-0-/-butyidimethyIsil34-P-D-gaIactopyranoside at 0-3 in 92% yield " phenyl l-thio-3-lactoside gave the 3 -sulftte in 76% yield, accompanied by 10% of the 3, 6 -disul te, and similar results were obtained with phenyl 2-acetamido-2-deoxy-l-thio-P-lactoside," " whereas the maltose derivative 51 reacted preferentially at 0-2. "... 

Maltose derivative (101) was converted into a corresponding glucosamine compound and the 5,6-acetal was then removed and inversion was effected at C-5 to lead to the heparin related compound (102). Related compounds were also described. The spacer modified oligosaccharide (103), which has the same number of atoms linking the sugar units as does the core of N-linked glycoconjugates, has been synthesised. ... 

Reactions carried out on disaccharide derivatives included the conversion of peracetates to l-phenylthio- 3-derivatives by use of phase-transfer methods and the epimerization at C-2 by calcium -amine systems (CaCl2.2H20, EtjN, for example). By this means maltose, lactose, isomaltose and melibiose were converted into the corresponding glucosyl-D-mannoses. An extensive range of variously substituted maltosyl fluorides have been made from maltose derivatives as substrates for cyclodextrin transferase. Only the 6 -methyl ether and 6 -acetate were transformed into cyclic products. In the course of the work the thio-derivatives (83) and (84) were made. ... 

The synthesis of maltose derivative 17, with a 3,2 -0-benzylidmie acetal bridging the two glucose residues, and its behaviour under hydrolytic, reductive, and oxidative cleavage conditions... 

Acetates and benzoates are widely used as characteristic derivatives of carbohydrates, and for the assay and protection of hydroxyl groups. Various maltose heptaacetates having a free hydroxyl group on C-l, C-2, C-3, C-6, or C-6 have been synthesized. 2,3,6,2, 3, 4, 6 -Hepta-0-acetyl-/3-maltose (17) has been prepared by hydrolysis of the corresponding glycosyl halide.57,58 The reaction conditions may not always result in the isolation of the anomerically unsubstituted acetate, as was shown by Corbett and coworkers,59 who obtained three... 

The cyclic acetals of sugars constitute an important class of compounds, and their value as synthetic intermediates is well recognized.100 The reaction of methyl /3-maltoside with benzaldehyde in the presence of zinc chloride has been reported to give the crystalline methyl 4, 6 -0-benzylidene-/3-maltoside.52 Similar benzylidenation of l,6-anhydro-/8-maltose affords the corresponding 4, 6 -0-benzylidene derivative in 63% yield.82... 

Because 6-deoxyhex-5-enopyranose derivatives can be readily converted into 2-deoxyinososes,91 5-bromides (for example, 164) give useful access to such carbocyclic compounds.92 In this way, octa-0-acetyl-/ -maltose was converted by treatment with zinc-acetic acid into the 5-ene by way of the corresponding 5-bromide 30 and thence into the pseudo-disaccharide compound (169) which is related to components of members of the aminoglycoside antibiotic series.36... 

The problem of the acid-catalyzed hydrolysis of the carbohydrate orthoesters was brought nearer to the final solution by Pacsu s experiments on the hydrolysis of maltose methyl 1,2-orthoacetate. Since two adjacent hydroxyl groups on the same side of the plane are necessary for the formation of orthoester derivatives, the maltose methyl orthoacetate must have an -configuration. Hydrolytic experiments with very dilute hydrochloric acid confirmed this. Two consecutive reactions took place at a pH of 4. In the first reaction, the original specific rotation, Co ]d - -103.7 in pure water, increased to -1-134.6° within two minutes. The latter figure corresponds to the specific rotation of a-maltose 2-acetate. The second reaction k = 0.0095) corresponded to the downward muta-rotation of a-maltose 2-acetate. When the hydrogen-ion concentration,... 

Product Inhibition. In most microbiological and biochemical systems accumulation of end products exercises an inhibitory effect on the rate of the forward reaction. Stimulation by end product is thermodynamically improbable. One of the major products of hydrolysis of cellulose is cellobiose. There is a stimulation by cellobiose of Cx activity of Streptomyces spp. filtrates only when the substrate is solubilized by the introduction of various substituents—e.g., CMC, hydroxycellulose, cellulose acetate, etc. Stimulation is absent when unsubstituted cellulose is used (14). On the other hand, product inhibition is common. Cellobiose inhibits the hydrolysis of cellulose by filtrates of most of the 36 organisms tested. This action of cellobiose is believed to be that of an end product inhibiting an enzymatic hydrolysis in much the same manner that maltose inhibits hydrolysis of starch by a-amylase. The inhibitory effect of products varies with the organism from which the cellulase is derived. Thus, lactose is a very good inhibitor of the enzyme from... 

The readily accessible peracetates of lactose, maltose, and melibiose are converted in good yields into the corresponding 1,2-trans glycobiosyl azide hepta-acetates more conveniently than by the previously published procedure for the preparation of hepta-(9-acetyl-p-cellobiosyl azide (59). Later this formation of hepta-(9-acetyl-p-lactosyl azide (60) was reported as a novel procedure, and the corresponding melibiosyl derivative was again described. Compound 59 can also be obtained from an orthoester precursor with trimethylsilyl azide as already described, but this route does not enjoy any particular preparative advantage. 

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