Enzymic .beta.-Galactosidation of Modified Monosaccharides: Study of the Enzyme Selectivity for the Acceptor and Its Application to the Synthesis of Disaccharides

Enzymatic syntheses and selective hydrolysis of O-β-d-galactopyranosides using a marine mollusc β-galactosidase

“…The b-anomer of the same acceptor in the same conditions furnished a mixture of products in which the b-1-3 was the predominant isomer 9 (60%) over the b-1-4, 10 (40%). 13 The yields (ca. 33%) in both cases were moderate at 5-molar excess of acceptors.…”

“…The spectra of 13 (b-1-3) and 14 (b-1-4) regioisomers are in accord to those reported. 13 The spectrum of b-1-2 regioisomer, 15 was characterized by the diagnostic xylose H2 signal at 3.94 ppm ( Table 2). Compounds 13, 14 and 15 after deprotection were used for the analysis of hydrolytic activity of the enzyme (see below).…”

“…Owing to the specificity of acceptor site of most galactosidases for compounds with phenyl groups, 13 the yields obtained in the reactions using free or methyl derivative of xylose and methyl b-galactopyranoside and D D-galactose, are interestingly high. In fact, for example, the enzyme from A. oryzae was reported to have a very low affinity for these polar acceptors thus resulting in low yield using the same acceptor excesses 17 and the E. coli b-galactosidase catalyzed the synthesis of 6 in 33% yield using, as in our case, 10-fold molar excess of methyl b-D D-xylopyranoside.…”

“…In fact, for example, the enzyme from A. oryzae was reported to have a very low affinity for these polar acceptors thus resulting in low yield using the same acceptor excesses 17 and the E. coli b-galactosidase catalyzed the synthesis of 6 in 33% yield using, as in our case, 10-fold molar excess of methyl b-D D-xylopyranoside. 13 Moreover no product formation was observed using b-galactosidase from bovine testes and a polar acceptor such as 2-deoxy-D Dgalactopyranose. 18 Another interesting characteristic of this enzyme is the uncommon b-1-3 selectivity in the transgalactosylation reactions with most of the acceptors.…”

Enzymes in the Synthesis of Bioactive Compounds: The Prodigious Decades

“…For instance, it has been shown that both the nature of the substituent and the anomeric configuration influence the regioselectivity and the yield of the glycosidation. 69 iii) Manipulation of the medium, using organic cosolvents to reduce the total volume of water. Also, addition of salts at high concentration has been used in order to reduce the water activity.…”