Tri-O-acetyl-p-D-xylopyranosyl chloride

In addition to its role on the equilibrium concentrations of two possible carbon-1 isomers (i.e. anomers), the anomeric effect also influences the conformational populations of a given isomer. Thus tri-O-acetyl-P-D-xylopyranosyl chloride exists in the C4 conformation (9b) having the benefit of the anomeric effect. Scheme 3, in spite of severe 1,3-syn diaxial interactions (40). Similarly a-D-idopyranose pentacetate exists in the conformation (10a) rather than the 4 conformation (10b) 5). 

In the solid state, tri-O-acetyl-p-D-xylopyranosyl halides adopt the all-equatorial 4Ci conformation, -whereas tri-O-benzoyl-p-D-xylopyranosyl halides crystallize in the all-axial 1C4 conformation, except for tri-O-benzqyl-p-D-xylopyranosyl chloride, which adopts the (skew) conformation. The variations of bond lengths to the anomeric carbon atom are discussed with regard to the anomeric effect. By comparative studies of the conformational equilibria of acetylated and benzoylated 1,5-anhydropentitols on the one hand, and pentopyranoses exhibiting the anomeric effect on the other, data for the non-bonding interactions may be derived. Based on the principle of additivity of these factors, the conformational distribution of structurally related compound may be estimated. In connection with these results, it is noted that two benzoyl groups show a smaller 1,3-diaxial interaction than two acetyl groups the difference between these interactions is about... 

Cl 1H12N8O11, 2-Methyl-5- N-nitrocarboxamido)-1-(2, 3, 5 -tri-0-nit-ro- -D-ribofuranosyl)imidazol-4-carboxamide, 46B, 433 Cl1H13NO7, p-Nitrophenyl- -D-xylopyranoside, 42B, 319 Cl1H15BrN20n, Arabinose p-bromophenylhydrazone, 27, 790 Cl 1H1 sBrN20i, Ribose-p-bromophenylhydrazone, 29, 489 C11H15CIO7, 2,3,4-Tri-O-acetyl- -D-xylopyranosyl chloride, 40B, 391 1,3,4-Tri-0-acetyl-2-desoxy-2-fluoro-a-D-xylopyranose,... 

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