Synthesis of acylated methyl -β-d-xylopyranosides and their enzymic deacylations by rabbit serum esterases

Pivaloylated glucoconjugates with heterocyclic oximes

“…Synthesis Glucoconjugates (5)(6)(7) with N-glycosyl bond were synthesized from tetra-O-pivaloyl-α-d-glucopyranosyl bromide (1) with three different heterocyclic oximes: 3-hydroxyiminoquinuclidine (2), 4-hydroxyiminomethylpyridine (3) and N-methyl-2-hydroxyiminomethylimidazole (4). Pivaloylation of β-d-glucopyranose in pyridine with a 10-fold molar excess of pivaloyl chloride produced penta-Opivaloyl-β-d-glucopyranose [7] which was, after isolation and purification, treated with HBr (33% in glacial acetic acid) to give the starting tetra-O-pivaloyl-α-d-glucopyranosyl bromide (1) [2,7].…”

“…It can be introduced selectively to produce various partially pivaloylated saccharides, its position in a molecule is easily detectable by 1 H NMR, and it can be removed totally or selectively by esterases from mammalian sera [2,[4][5][6]. Furthermore, the pivaloyl group has been used in carbohydrate chemistry because of its advantageous stereodirecting properties in glycosylation reactions.…”

Methyl 2,3,4-tri-O-pivaloyl-β-D-xylopyranoside

“…Several series of acylated monosaccharides, the acyl groups being pivaloyls, acetyls or a combination of the two, have been synthesized (Ljevakovic  et al, 1992;Tomic  et al, 1991;Petrovic  et al, 2002). One of the series of acylated monosaccharides previously prepared was that of methyl -d-xylopyranoside, of which methyl 2,3,4-tri-O-pivaloyl--d-xylopyranoside, (I), is the completely acylated analog (Petrovic  et al, 1997). In carbohydrates, the hydroxyl groups are of comparable reactivity.…”

“…The pivaloyl group is of special interest since it can be introduced into carbohydrates regioselectively, making further transformations selective as well. It can also be removed selectively by enzymes isolated from mammalian sera (Petrovic  et al, 1997;Tomic  et al, 1991). Therefore, hydroxyl-group protection by pivaloyls leads to interesting new substrates in the investigation of enzymes as catalysts in organic synthesis.…”

Synthesis and Enzymic Hydrolysis of Acylated Adenosine Derivatives

“…[18] It has also been shown that the free 5 0 -hydroxyl group of partially acetylated adenosines plays a crucial role in the catalytic action at the adenosine deaminase (ADA) active site. [19] In continuation of our interest in enzymic transformations of carbohydrates, [20,21] in this work we turn to acylated adenosine derivatives in an attempt to perform regioselective enzymically catalyzed deprotection of the 5 0 -OH.…”