Optimized disaccharides

Fig. 3. Projections on the (<1>, maps of the CICADA conformational search of the pentasaccharide. The dots indicate the values of all the optimized conformations determined by CICADA at each glycosidic linkange in 8 kcal/mol energy window For comparison, the isocontours, drawn in 1 Kcal/mol steps with an outer limit of 8 kcal/mol, represent the energy level of each disaccharide and calculated with the relaxed grid search approach. Dashed regions represent the locations of the low energy conformation of the pentasaccharide plotted on the potential energy surfaces of the constituting disaccharide segments...

As shown in Table II, the optimal value of the rotation angle per disaccharide unit around the helix axis, for a free... 

This general overview may be illustrated by an example treatment of 3,4-di-0-acetyl-2,6-dideoxy-a-D- ara-bino-hexopvranosvl bromide (9) with methyl 4-0-acetyl-2.6-dideoxv-a-D -lvxo-hexopvranoside (W) under systematically developed and adjusted conditions gave in 56% optimized yield both the a-(l->3)- and the p-(l->3)-linked disaccharides 11 and 12 in the ratio of approximately 2 1 separation step is required. Consequently, stereoselective or even better stereospecific solutions for the preparation of these oligosaccharides would be certainly appreciated. 

On their side, Yin and Linker [216] made use of a 2-C-branched hexopyranoside, the synthesis of which was achieved by addition of dimethyl malonate to tri-O-benzyl-D-glucal (TUPAC name 3,4,6-tri-0-benzyl-l,5-anhydro-2-deoxy-D-araZtino-hex-l-enitol, Scheme 45) [217], Thus, saponification of the 2-C-[bis(meth-oxycarbonyl)]methyl derivative 184 to the corresponding malonic acid 185 was followed by heating in refluxing toluene. This led to decarboxylation and lactoniza-tion giving 186. The method was optimized and applied to the synthesis of pentoses and disaccharides. 

A major undertaking was initiated in 1950 by Pacsu and Mora,104 and later continued by Mora and colleagues, to establish optimal conditions for the condensation polymerization of simple sugars, both mono- and disaccharides. These studies also involved the preparation of derivatives of polyglucose [containing —CO H, —OSO H, —0N02, —0—CHjCHjNH, ... 

RCM with Schrock catalyst, 28 synthesis, 28-29 yield optimization, 40-41 (l->4)-P-0-Disaccharides, 24/ 4-DMAJP (4-dimethylaminophenol),... 

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