Multigram-scale synthesis of l,d-heptoside using a Fleming-Tamao oxidation promoted by mercuric trifluoroacetate

Expedient synthesis of l-heptose derived septacidin building blocks from l-glucose

Bacterial natural products containing heptosides such as septacidin represent interesting scaffolds for the development of drugs to combat antimicrobial resistance. However, very few synthetic strategies have been reported to grant access to these derivatives. Here, we have devised a synthetic pathway to l-glycero-l-glucoheptoside, a key building block en route to septacidin, directly from l-glucose. Importantly, we show that carbon homologation at C6, encompassing oxidation of the C6-OH followed by methylenation, is significantly influenced by the nature of the C4-moiety. In order to observe the effect of various patterns, namely azide (N3), p-methoxybenzyloxy (OPMB), and benzyloxy (OBn), a thorough analysis was conducted on the corresponding l-glucosides. The results unveiled a distinct trend where the efficiency of methylenation followed the trend OBn > OPMB > N3. Finally, the C6-alkene was dihydroxylated in the presence of osmium tetroxide to yield the expected l/d-glycero-l-glucoheptosides. The lead building block, which features a C-4 azide, was delivered as a phenyl thioglycoside. Added to the suitable masking of the 6,7-diol, this combination enables further functionalization to achieve versatile compounds of biological interest. The study insights into the interplay between substitution at C-4 and carbon homologation at C-6 provide valuable guidance for future endeavors in the synthesis of these carbohydrate molecules.

Stereoselective Synthesis of β-d-Manno-heptopyranoside via Cs2CO3-Mediated Anomeric O-Alkylation: Synthesis of a Tetrasaccharide Repeat Unit of Bacillus thermoaerophilus Surface-Layer Glycoprotein

Stereoselective synthesis of d-glycero- and l-glycero-β-d-mannoheptosides has been achieved by cesium carbonate-mediated β-selective anomeric O-alkylation of the corresponding d-mannoheptoses. In addition, this method has been utilized in the total synthesis of a tetrasaccharide repeat unit of Bacillus thermoaerophilus surface-layer glycoprotein.

Pathogen-Associated Molecular Patterns: The Synthesis of Heptose Phosphates and Derivatives

Lipopolysaccharide biosynthesis metabolites, such as d-glycero-β-d-manno-heptopyranosyl 1,7-diphosphate, d-glycero-β-d-manno-heptopyranosyl phosphate, and adenosine 5′-(l-glycero-β-d-manno-heptopyranosyl)diphosphate, have been found to activate NF-κB via alpha-kinase 1 and TRAF-interacting protein with forkhead associated domain. This axis has been determined as a novel pathway of innate immunity yet to be targeted for immunomodulatory treatment approaches. Key in understanding this new axis has been the ability to synthesize these metabolites. The design of synthetic analogues and probes have also been published not only to design new drugs, but also to gain insight into the mechanism of action for these compounds. The focus of the present review is the synthesis of heptose phosphate metabolites­ as well as synthetic analogues and probes.

1 Introduction

2 Synthesis of d-glycero-d-manno-Heptose

2.1 Using d-Mannose as Starting Material

2.2 Using d-Ribose as Starting Material

2.3 Using 2,2-Dimethyl-1,3-dioxan-5-one as Starting Material

3 Synthesis of l-glycero-d-manno-Heptose

3.1 Using d-Mannose as Starting Material

3.2 Using 2,2-Dimethyl-1,3-dioxan-5-one as Starting Material

3.3 Using l-Lyxose as Starting Material

4 Synthesis of Heptose Phosphates

4.1 Synthesis of d-glycero-β-d-manno-Heptose 1,7-Diphosphate

4.2 Synthesis of Heptose Phosphate Derivatives

4.2.1 Development of Scaffolds for Conjugation

4.2.2 Development of Heptose Phosphates Derivatives for Cell Intake and Metabolic Stability

5 Conclusion and Outlook

Synthesis of l-glycero- and d-glycero-d-manno-Heptose Building Blocks for Stereoselective Assembly of the Lipopolysaccharide Core Trisaccharide of Vibrio parahemolyticus O2

Synthesis of bacterial cell surface l-glycero-d-manno-heptose (l,d-Hep)- and d-glycero-d-manno-heptose (d,d-Hep)-containing higher carbon sugars is a challenging task. Here, we report a convenient and efficient approach for the synthesis of the l,d-Hep and d,d-Hep building blocks. Using l-lyxose and d-ribose as starting materials, this approach features diastereoselective Mukaiyama-type aldol reactions as the key steps. On the basis of the synthetic l,d-Hep and d,d-Hep building blocks, we achieved the first stereoselective synthesis of the unique α-l,d-Hep-(1→3)-α-d,d-Hep-(1→5)-α-Kdo core trisaccharide of the lipopolysaccharide of Vibrio parahemolyticus O2.