Synthesis and application of bacterial exopolysaccharides

Bio-organic Synthesi

Neighboring-group participation by C-2 acyloxy groups: influence of the nucleophile and acyl group on the stereochemical outcome of acetal substitution reactions

A single acyloxy group at C-2 can control the outcome of nucleophilic substitution reactions of pyran-derived acetals, but the extent of the neighboring-group participation depends on a number of factors. We show here that neighboring-group participation does not necessarily control the stereochemical outcome of acetal substitution reactions with weak nucleophiles. The 1,2-trans selectivity increased with increasing reactivity of the incoming nucleophile. This trend suggests the intermediacy of both cis-fused dioxolenium ions and oxocarbenium ions in the stereochemistry-determining step. In addition, as the electron-donating ability of the neighboring group decreased, the preference for the 1,2-trans products increased. Computational studies show how the barriers for the ring-opening reaction on the dioxolenium ions and the transition states to provide the oxocarbenium ions change with the electron-donating capacity of the C-2-acyloxy group and the reactivity of the nucleophile.Neighboring-group participation by C-2 acyloxy groups can control the 1,2-trans stereoselectivity of acetal substitution reactions with the employment of strong nucleophiles. 1,2-Trans selectivity increases with decreased electron-donating ability of the acyloxy groups at C-2.image.Bio-organic Synthesi

Synthesis of unsymmetrical difluoromethylene bisphosphonates

Bio-organic Synthesi

Synthesis of 2-azido-2-deoxy- and 2-acetamido-2-deoxy-D-manno derivatives as versatile building blocks

Reported herein is the synthesis of a number of building blocks of 2-amino-2-deoxy-d-mannose from common d-glucose precursors.Bio-organic Synthesi

Assembly of a library of pel-oligosaccharides featuring α-glucosamine and α-galactosamine linkages

Pseudomonas aeruginosa, a pathogenic Gram-negative bacterium for which currently antibiotic resistance is posing a significant problem and for which no vaccines are available, protects itself by the formation of a biofilm. The Pel polysaccharide, a cationic polymer composed of cis-linked galactosamine (GalN), N-acetyl galactosamine (GalNAc), glucosamine (GlcN) and N-acetyl glucosamine (GlcNAc) monosaccharides, is an important constituent of the biofilm. Well-defined Pel oligosaccharides will be valuable tools to probe the biosynthesis machinery of this polysaccharide and may serve as diagnostic tools or be used as components of glycoconjugate vaccines. We here, report on the development of synthetic chemistry to access well-defined Pel-oligosaccharides. The chemistry hinges on the use of di-tert-butylsilylidene protected GalN and GlcN building blocks, which allow for completely cis-selective glycosylation reactions. We show the applicability of the chemistry by the assembly of a matrix of 3 × 6 Pel heptasaccharides, which has been generated from a single set of suitably protected Pel heptasaccharides, in which a single glucosamine residue is incorporated and positioned at different places along the Pel oligo-galactosamine chain.ERC-CoG-726072-“GLYCONTROL”Bio-organic Synthesi

Organic dye-sensitized nitrene generation: intermolecular aziridination of unactivated alkenes

Bio-organic SynthesisMetals in Catalysis, Biomimetics & Inorganic Material

The influence of acceptor acidity on hydrogen bond mediated aglycone delivery (HAD) through the picoloyl protecting group

Bio-organic Synthesi

Halogen atom participation in guiding the stereochemical outcomes of acetal substitution reactions

Bio-organic Synthesi

Teichoic Acids: Synthesis and Applications

Bio-organic Synthesi

Synthesis of the Staphylococcus aureus Strain M Capsular Polysaccharide Repeating Unit

Bio-organic Synthesi