A novel enzymatic method for the synthesis of disaccharide fatty acid esters was developed with immobilized Mucor miehei lipase (Lipozyme IM-60; Novo Nordisk, Bagsvaerd, Denmark) as a catalyst. A range of lactose and maltose monoesters was prepared in overall yields of 48-77% from the corresponding sugar acetals and fatty acids.KEY WORDS: Enzymatic esterification, lactese~esters, lip~e~ maltose~ esters, sugar fatty acid esters.Enzymatic approaches to the production of suga~based stm factants have been actively explored over the last few years (1,2}. The main advantages associated with the use of biocatalysts are mild reaction conditions and the high regioselectivity typically displayed by enzyme~ Although nume~ ous recent reports have dealt with the preparation of monosaccharide (3-11) and alkyl glycoside esters (12-14), the synthesis of disaccharide esters still remains a challenging problem_ This is due to the low solubility of disaccharides in those organic solvents that are generally considered suitable for biocatalysis, whereas only a few enzymes are known to retain their catalytic activity in pyridine or DMSO, which can solubilize these sugars at high concentrations (3).To circumvent this problem, we have adopted an alternative approach previously developed for the preparation of monosaccharide fatty acid esters (9), namely the acetalization of disaccharides was attempted to improve their solubility in or miscibility with fatty acids, thus avoiding the use of highly polar solvents in the reaction medium. This communication describes the synthesis of lactose and maltose monoesters enzymatically prepared from the co~ responding disaccharide acetals. The final products were ol> tained in good yields after acid-catalyzed cleavage of the acetal groups.
The photocrosslinking mechanism of copolymers of styrene (ST) with 4-vinylbenzyl selenocyanate (VBSe), 4-vinylbenzyl thiocyanate (VJ3T) or 4-vinylbenzyl bromide (VBBr) was investigated using low-molecular-weight model compounds. The photochemistry of benzyl selenocyanate was studied by means of 'H NMR spectroscopy and gas chromatography/mass spectrometry (GC/MS) analysis. It was found that a cleavage in benzyl and selenocyanato radicals and -to a minor extent -in benzylseleno and cyano radicals occurs. A comparative study of the products which are formed during the photolysis of benzyl selenocyanate, benzyl thiocyanate and benzyl bromide in cumene shows that selenocyanato and thiocyanato radicals have far less hydrogen abstraction efficiency than bromine radicals. The results are discussed in regard to the reactions of the corresponding copolymers. A comparison with a crosslinking mechanism, proposed for chloromethylated polystyrene under irradiation, is carried out.
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