Total Synthesis of the Photorhabdus temperata ssp. Cinereal 3240 Zwitterionic Trisaccharide Repeating Unit

On resin synthesis of phosphoethanolamine cellulose

Phosphoethanoamine (pEtN) cellulose is a chemically modified cellulose present in some bacterial biofilms. To deepen our understanding of this biopolymer and its biological function, access to chemically defined pEtN-cellulose oligosaccharides is desirable. Herein, we report an on resin protocol for the fast synthesis of tailor-made pEtN-celluloses. The cellulose backbone is prepared by automated glycan assembly and then specifically functionalized with pEtN groups, allowing for access to a collection of ten pEtN-cellulose oligomers with different amount and pattern of pEtN.

A Hitchhiker's Guide to Problem Selection in Carbohydrate Synthesis

Oligosaccharides are ubiquitous in molecular biology and are used for functions ranging from governing protein folding to intercellular communication. Perhaps paradoxically, the exact role of the glycan in most of these settings is not well understood. One reason for this contradiction concerns the fact that carbohydrates often appear in heterogeneous form in nature. These mixtures complicate the isolation of pure material and characterization of structure-activity relationships. As a result, a major bottleneck in glycoscience research is the synthesis and modification of pure materials. While synthetic and chemoenzymatic methods have enabled access to homogeneous tool compounds, a central problem, particularly for newer synthetic chemists, is the matter of problem selection. This outlook aims to provide an entry level overview of fundamental principles in carbohydrate chemistry with an eye toward enabling solutions to frontier challenges.

General Synthetic Approach to Diverse Taxane Cores

Chemical synthesis of natural products is typically inspired by the structure and function of a target molecule. When both factors are of interest, such as in the case of taxane diterpenoids, a synthesis can both serve as a platform for synthetic strategy development and enable new biological exploration. Guided by this paradigm, we present here a unified enantiospecific approach to diverse taxane cores from the feedstock monoterpenoid (S)-carvone. Key to the success of our approach was the use of a skeletal remodeling strategy which began with the divergent reorganization and convergent coupling of two carvone-derived fragments, facilitated by Pd-catalyzed C-C bond cleavage tactics. This coupling was followed by additional restructuring using a Sm(II)-mediated rearrangement and a bioinspired, visible-light induced, transannular [2 + 2] photocycloaddition. Overall, this divergent monoterpenoid remodeling/convergent fragment coupling approach to complex diterpenoid synthesis provides access to structurally disparate taxane cores which have set the stage for the preparation of a wide range of taxanes.

Chemical Synthesis of a Colanic Acid Hexasaccharide

Chemical synthesis of a hexasaccharide relevant to colanic acid, which bears a high prevalence of polyanionic and acetyl decoration, has been achieved, highlighting stereoselective glycosylation and effective installation of O-acetyl and pyruvate residues.

Synthesis of Phosphatidyl Glycerol Containing Unsymmetric Acyl Chains Using H-Phosphonate Methodology

Naturally occurring phospholipids, such as phosphatidyl glycerol (PG), are gaining interest due to the roles they play in disease mechanisms. To elucidate the metabolism of PG, an optically pure material is required, but this is unfortunately not commercially available. Our previous PG synthesis route utilized phosphoramidite methodology that addressed issues surrounding fatty acid substrate scope and glycerol backbone modifications prior to headgroup phosphorylation, but faltered in the reproducibility of the overall pathway due to purification challenges. Herein, we present a robust pathway to optically pure PG in fewer steps, utilizing H-phosphonates that features a chromatographically friendly and stable triethyl ammonium H-phosphonate salt. Our route is also amendable to the simultaneous installation of different acyl chains, either saturated or unsaturated, on the glycerol backbone.

Total Synthesis of the Phosphorylated Zwitterionic Trisaccharide Repeating Unit of Photorhabdus temperata cinerea 3240

Herein, we report the total synthesis of the phosphorylated zwitterionic trisaccharide repeating unit of Photorhabdus temperata subsp. cinerea 3240. The efficient route involves regio- and stereoselective assembly of trisaccharide with rare deoxyamino sugar AAT at the nonreducing end, late stage oxidation, and installation of a phosphate linker on the trisaccharide. The total synthesis was completed via a longest linear sequence of 24 steps in 6.5% overall yield.