A glycosidase

Pancreatic (a) amylase is an endoglycosidase, which removes maltose units from amylose or amylopectin. It splits the a-1,4 glycoside bond. In the absence of an a-1,6 glycosidase, limit dextrin is a product in addition to maltose. Sucrose is nonreducing lactose is reducing. 

Cycloaddition reaction of nitrone (—)-(394) with dimethyl maleate D14 has been used for the synthesis of two new polyhydroxyl pyrrolizidines (687) and (688) (Schemes 2.293, 2.294). These compounds are analogs of alkaloids ros-marinecine and crotanecine, which were assayed for their inhibitory activities toward 22 commercially available glycosidase enzymes. One of them ((-)- a-epi-crotanecine) (—)-(688) is a potent and selective inhibitor of a-mannosidases (310). The reaction of (—)-(394) with dimethyl maleate gave a 9.6 6 1 mixture of cycloadducts (—)-(680), (+ )-(680), and (—)-(681), which arise from anti-exo,... 

Related imino alditols such as azepanes or lactam derivatives have been obtained and have shown to be glycosidase inhibitors [96, 100]. Both d- and l-gulonolactone have been converted into polyhydroxylated 1,6-aldonolactams of type 79 in a sequence of straightforward functional transformations, including sulfinylation of the corresponding aldonolactone-derived acetonides 76 that gave 5,6-cyclic sulfites 77 (Scheme 23) [101]. The latter reacted with sodium azide... 

Bacillus circulans P-galactosidase prefers 1,4-glycosidic bond formation and ha been used in the large-scale synthesis of IV-acetyllactosamine (7). Coupled with a oi2,6-sialyltransferase, the disaccharide 7 was converted to the sialyldisaccharide, which is nc longer subject to the glycosidase-catalyzed hydrolysis, thus improving the yield (set experimental section) [35]. 

This article reviews the main applications of glycosidases and lipases in the synthesis of glycosidic bonds and in acylation/deacylation reactions of carbohydrates, respectively. Special attention is given to the factors that can affect the selectivity of the reactions, such as the enzyme origin, the structure of the substrates, and the reaction medium. A number of reviews have appeared in the literature on enzymatic synthesis of carbohydrates that include reactions with glycosidases and/or lipases [ 1 - 6]. In this article only a selection of examples are given to illustrate the discussion, rather than an extensive compilation of the work published in the area. 

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