3-Nitro-2-pyridyl glycoside as donor for chemical glycosylation and its application to chemoenzymatic synthesis of oligosaccharide

Leloir Glycosyltransferases in Applied Biocatalysis: A Multidisciplinary Approach

Enzymes are nature’s catalyst of choice for the highly selective and efficient coupling of carbohydrates. Enzymatic sugar coupling is a competitive technology for industrial glycosylation reactions, since chemical synthetic routes require extensive use of laborious protection group manipulations and often lack regio- and stereoselectivity. The application of Leloir glycosyltransferases has received considerable attention in recent years and offers excellent control over the reactivity and selectivity of glycosylation reactions with unprotected carbohydrates, paving the way for previously inaccessible synthetic routes. The development of nucleotide recycling cascades has allowed for the efficient production and reuse of nucleotide sugar donors in robust one-pot multi-enzyme glycosylation cascades. In this way, large glycans and glycoconjugates with complex stereochemistry can be constructed. With recent advances, LeLoir glycosyltransferases are close to being applied industrially in multi-enzyme, programmable cascade glycosylations.

Synthesis and stereochemical determination of an antiparasitic pseudo-aminal type monoterpene indole alkaloid

5-Nor stemmadenine alkaloids, isolated from the genus Tabernaemontana, display a range of bioactivity. 16-Hydroxy-16,22-dihydroapparicine, the active component of an extract from the Tabernaemontana sp. (dichotoma, elegans, and divaricate), exhibited potent antimalarial activity, representing the first such report of the antimalarial property of 5-nor stemmadenine alkaloids. We, therefore, decided to attempt the total synthesis of the compound to explore its antimalarial activity and investigate structure and bioactivity relationships. As a result, we completed the first total synthesis of 16-hydroxy-16,22-dihydroapparicine, by combining a phosphine-mediated cascade reaction, diastereoselective nucleophilic addition of 2-acylindole or methylketone via a Felkin-Anh transition state, and chirality transferring intramolecular Michael addition. We also clarified the absolute stereochemistries of the compound. Furthermore, we evaluated the activity of the synthetic compound, as well as that of some intermediates, all of which showed weak activity against chloroquine-resistant Plasmodium falciparum (K1 strain) malaria parasites.

Synthesis of betaglycan-type tetraosyl hexapeptide: a possible precursor regulating enzymatic elongation toward heparin

TETRAOSYL HEXAPEPTIDE, A PART OF THE SEQUENCE OF BETAGLYCAN: beta-D-GlcA-(1-->3)-beta-D-Gal-(1-->3)-beta-D-Gal-(1-->4)-beta-D-Xyl-(1-->O-SerGlyTrpProAspGly (1), which was designed as a probe for glycan elongation toward heparin, was synthesized in a stereocontrolled manner.

A substrate-unspecified glycosylation reaction promoted by copper(II) trifluoromethanesulfonate in benzotrifluoride

A glycosylation reaction induced by copper(II) trifluoromethanesulfonate is described. Using benzotrifluoride as the reaction solvent, five kinds of glycosyl donors, a glucosyl chloride, a fluoride, a trichloroacetimidate, a 1-O-acetyl compound, and a lactol were activated to give the corresponding glucosides.