H-Phosphonate Synthesis and Biological Evaluation of an Immunomodulatory Phosphoglycolipid from Thermophilic Bacteria

N-glyceroyl alkylamine phosphoglycolipids dominate the lipidome of several Bacillota bacteria

Elucidation of the membrane lipid composition of bacteria can help to better understand how bacterial cells interact with their surroundings, adapt to environmental stress, and resist antimicrobial agents. Here we describe for the first time the detection of a wide array of N-glyceroyl alkylamine phosphoglycolipids (NGAPs) in a range of Bacillota bacteria (formerly Firmicutes). Bacillota includes a diverse range of bacteria that are typically highly resistant to harsh conditions such as heat, radiation, and pH, allowing the bacteria to survive in unfavorable environments. In 9 out 18 investigated strains of Bacillota, spread across 5 orders (Thermoanaerobacterales, Thermosediminibacterales, Eubacteriales, Halanaerobiales, and Sulfobacillia) mild acid hydrolysis released N-glyceroyl alkylamines (NGAs), which were detectable by gas chromatography-mass spectrometry (GC-MS) during routine fatty acid analysis. One strain, Moorella thermoacetica was found to produce long-chain NGAs (C30-C32), which are postulated to have isodiabolic acid-like structures. A wide variety of intact polar NGAPs were identified using ultra-high pressure liquid chromatography high resolution multi-stage mass spectrometry (UHPLC-HRMSn). These include many previously undescribed lipids with a variety of sugar moieties and glycerol-bound core lipid moieties, including ether-bound components and alkyl 1,2-diols. The NGAPs constituted the majority of the intact polar lipid composition of these strains and presumably contribute to their tough cell membranes. The presence of NGAs in Bacillota appears to be associated with thermophilia. Both the hydrolysis-derived NGAs and intact polar NGAPs have potential to be biomarkers for extremophilic and, in particular, thermophilic bacteria.

Phosphate-Containing Glycolipids: A Review on Synthesis and Bioactivity

Phosphate-containing glycolipids (PcGL) are scarcer than the better understood glycolipids. They are composed of arrangements of phosphate, carbohydrates and glycerol units and are always found associated with lipids. PcGL are often found associated with cell membranes, suggesting they play roles in cell membrane structure and intercellular interactions. This article aims to provide an up-to-date overview of the existing knowledge and research on PcGL, emphasizing their synthesis and wide range of biological activities. When it comes to the synthesis of PcGL compounds, the strategies for glycosylation mainly rely on the thioglycoside donor, the trichloroacetamidate donor and halide donor strategies, while phosphorylation is stapled and falls on either phosphite chemistry or phosphoryl chloride chemistry. Certain bacteria utilize PcGLs in their pathogenicity, triggering an inflammatory response within the host's defense mechanisms. The best-known examples of these structures are teichoic acids, lipopolysaccharide and the capsular polysaccharide found in bacteria, all of which are frequently implicated in bacterial infections. Given the degree of variability within PcGL structures, they were found to display a wide range of bioactivities. PcGL compounds were found to: (1) have anti-metastatic properties, (2) behave as agonists or antagonists of platelet aggregation, (3) be mostly pro-inflammatory, (4) display antifungal and antibiotic activity and (5) have neurogenic activity.

Bis(2,2,2 trifluoroethyl) Phosphonate as a Convenient Precursor for the Synthesis of H-Phosphonates

A microwave-assisted synthesis of dialkyl and cyclic H-phosphonates via bis(2,2,2 trifluoroethyl) phosphonate (BTFEP) is described. This method enables the synthesis of various cyclic H-phosphonates and hetero-substituted dialkyl H-phosphonates by simple alcoholysis under non-inert and additive-free conditions. Short reaction times and the requirement for only stoichiometric amounts of alcohol render this method attractive for synthetic applications.

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.