Sorbitol acylation

Amino-polyols, such as 1-aminodeoxy-D-sorbitol or D-(-l-)-glucosamine, as well as adenine, underwent selenenylation-acylation at the amino groups by dichloride 102 and thus their 2-benzisoselenazol-3(2//)-onyl derivatives 108 and 109 were obtained <2003SC1301> (Scheme 40). The organoselenium-modified /3-CDs 110 and 111 were synthesized in a similar way <2002HCA9>. 

The acylation of mono- and oligosaccharides and their derivatives, mainly sorbitol and sucrose, with higher fatty acids yields surface-active agents and fat replacers. Hydrolysis of acyl groups can be achieved by either interesterification (water or alcohols) or ammonolysis. 

Among other surface active esters, polyglycol esters of fatty acids, alkanoyl glycerol acetates and lactates, alkyl lactates, esters of fatty acids and pentaerythritol, glucose, methylglucose, mannose, sucrose, and, especially, sorbitol are often exploited. The latter, sorbitan acylates, are particularly known as Spans , Arlacels , and Arlamol ISML - all of ICI production. These mild and low-toxic emulsifiers are widely applied in food, pharmaceutical, personal care and other consumer and industrial products. 

It has also been shown that lipase CA can produce reduced sugar-containing polyesters regioselectively from divinyl sebacate and sorbitol, in which sorbitol was exclusively acylated at the 1 and 6-positions (Scheme 23.11) [115]. Mannitol and meso-erythritol were also regioselectively polymerized with divinyl sebacate. The lipase CA-catalyzed polycondensation of adipic acid and sorbitol also took place in... 

Uyama et al. formed a similar polymer by a polymerization in acetonitrile between divinyl sebacate and sorbitol using 75%-by-wt Novozyme-43S. They reported that the polymerization proceeded by exclusive acylation at the sorbitol 1- and 6-positions. This difference in regioselectivity may be due to i) Uyanu et al. analyzed only a water-insoluble product fraction (64% of total), and/or ii) differences in the reaction conditions used (e.g. solvent vs. bulk). 

Unsaturation within the fatty acid chain did not disturb the process. In the polymerisation of divinyl sebacate and polyol (sorbitol), the regioselectivity was controlled to yield sugar-containing polyesters in which the 1- and 6-positions of sorbitol were regioselectively acylated. 

Polar solvents have a log P < 2, moderate solvents have a log P in the range 2apolar solvents log P > 4 (Table 1). Synthesis is best achieved in solvents of intermediate polarity that are able to partially solubilize both the sugar and enzyme, or in solvents with a log P value greater than 1.5 that do not affect the hydration shell of the enzyme and so denature the protein. Tertiary alcohols are particularly effective solvents in this respect as they cannot react with lipases due to steric hindrance at the hydroxy group and their boiling points facilitate their removal after reaction. tert-Butyl alcohol catalyzed by lipase has been employed for sugar acylations [40-42]. Other solvents that have been utilized include 2-pyrrolidone [43] for the synthesis of sorbitol ester derivatives. Pyridine and biphasic mixtures of solvents such as benzene/pyridine and tert-hvXy alcohol/hexane have also been used. 

Esters of fructose, sucrose, sorbitol, glucose separation by number of acyl groups... 

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