Synthesis and evaluation of the antibiotic-adjuvant activity of carbohydrate-based phosphoramidate derivatives

Phosphoramidates are becoming increasingly recognized as molecular targets for therapeutic development. Their biological functions are significantly influenced by their inherent properties such as reactivity, as well as the P-N backbone which allows for structural diversity. In this study we report the synthesis of novel carbohydrate-based phosphoramidate derivatives via the Staudinger-phosphite reaction; along with an evaluation of their adjuvant activity in combination with popular antibiotics. Our targets involved variation in both the sugar residue as well as the identity of the phosphoramidate. Moderate to excellent yields of these derivatives were obtained. Notable adjuvant activity was observed with the halogenated phosphoramidates. For the fluorinated glucose derivative in particular, a remarkable 32-fold decrease in the MIC of Ampicillin was obtained against Methicillin-resistant S. aureus.

Chemical Synthesis Elucidates the Key Antigenic Epitope of the Autism-Related Bacterium Clostridium bolteae Capsular Octadecasaccharide

The gut pathogen Clostridium bolteae has been associated with the onset of autism spectrum disorder (ASD). To create vaccines against C. bolteae, it is important to identify exact protective epitopes of the immunologically active capsular polysaccharide (CPS). Here, a series of C. bolteae CPS glycans, up to an octadecasaccharide, was prepared. Key to achieving the total syntheses is a [2+2] coupling strategy based on a β-d-Rhap-(1→3)-α-d-Manp repeating unit that in turn was accessed by a stereoselective β-d-rhamnosylation. The 4,6-O-benzylidene-induced conformational locking is a powerful strategy for forming a β-d-mannose-type glycoside. An indirect strategy based on C2 epimerization of β-d-quinovoside was efficiently achieved by Swern oxidation and borohydride reduction. Sequential glycosylation, and regioselective and global deprotection produced the disaccharide and tetrasaccharide, up to the octadecasaccharide. Glycan microarray analysis of sera from rabbits immunized with inactivated C. bolteae bacteria revealed a humoral immune response to the di- and tetrasaccharide, but none of the longer sequences. The tetrasaccharide may be a key motif for designing glycoconjugate vaccines against C. bolteae.

Mechanistic Insights into Statistical Co-Assembly of Metal Complexes

Statistical copolymerization plays a key role in many biological and technological processes; however, mechanistic understanding of the formation of analogous supramolecular counterparts remains limited. Herein, we report detailed insights into the supramolecular co-assembly of two π-conjugated PdII and PtII complexes, which in isolation self-assemble into flexible fibers and nanodisks, respectively. An efficient single-step co-assembly into only one type of nanostructure (fibers or nanodisks) takes place if any of the components is in excess. In contrast, equimolar mixtures lead to PdII -rich fiber-like co-assemblies by a statistical co-nucleation event along with a residual amount of self-sorted nanodisks in a stepwise manner.