Alditols esterification

Unlike neutral polysaccharides undermethylated acidic polysaccharides cannot be realkylated directly. The Hakomori procedure leads to esterification of uronic acid residues that on further treatment with base will undergo extensive p-elimination. Therefore the methylated acidic polymer should be carboxyl-reduced with LiAFH4 prior to realkylation. This is illustrated by our work (O Neill et al., 1986a) on the extracellular polysaccharide produced by Alcaligenes (ATCC 31555). After a single methylation an excess of branch points was observed which indicated incomplete methylation of position 2 of (l- 3)-linked glucose residues. To confirm this, the methylated polysaccharide was carboxyl-reduced, ethylated, and the alkylated alditol acetates analyzed by GLC-MS. The... 

For the last few years, Kobayashi s and Gross s groups have been independently working on the synthesis of alditol-based polyesters by lipases as catalysts for selective polyol polymerizations. Lipases and proteases are well known as providing regioselectivity during esterification reactions at mild temperatures. In addition to this, the use of... 

Alditols, particularly glycerol (I), ethylene glycol, sorbitol, and D-manni-tol, have widespread commercial applications, frequently as a result of their hygroscopic properties. The organic monoesters, particularly of long-chain fatty acids, may have surface-active properties which make them of interest as emulsifiers, but the usual conditions of commercial esterification produce anhydro derivatives simultaneously (Chapter VII). Nitrate esters are important as explosives and as pharmaceuticals. The acetal derivatives (Chapter IV) have been extensively prepared and studied, but as yet have found no practical application. 

The phospht lation of alditols, oligosaccharides, and glycoproteins by use of sodium phosphate in anhydrous media has been described, and a papct on the direct esterification of a dialkyl phoqthate with organic halides in the presence of silver oxide included a number of carbohydrate examples, such as the formation of peracetylated -D-galactosyl phosphate from a-acetobromogalactose. Chl(MO-W, -diisopropylaminoalkoxyphoq)hines [ROP(Cl)N(i-Pr)2J in P3mdine... 

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