Green synthesis of (R)-3-hydroxy-decanoic acid and analogs from levoglucosenone: a novel access to the fatty acid moiety of rhamnolipids.

Rhamnolipids (RLs) are highly valuable molecules in the cosmetic, pharmaceutic, and agricultural sectors with outstanding biosurfactant properties. In agriculture, due to their potential to artificially stimulate the natural immune system of crops (also known as elicitation), they could represent a critical substitute to conventional pesticides. However, their current synthesis methods are complex and not aligned with green chemistry principles, posing a challenge for their industrial applications. In addition, their bioproduction is cumbersome with reproducibility issues and expensive downstream processing. This work offers a more straightforward and green access to RLs, crucial to decipher their mechanisms of action and design novel potent and eco-friendly elicitors. To achieve this, we propose an efficient seven-step synthetic pathway toward (R)-3-hydroxyfatty acid chains present in RLs, starting from cellulose-derived levoglucosenone, with Michael addition, Baeyer-Villiger oxidation, Bernet-Vasella reaction, and cross-metathesis homologation as key steps. This method allowed the production of (R)-3-hydroxyfatty acid chains and derivatives with an overall yield ranging from 24% to 36%.

Selective enhancement of (6-4) photoproduct formation in dithymine dinucleotides driven by specific sugar puckering.

Four dinucleotide analogs of thymidylyl(3'-5')thymidine (TpT) have been designed and synthesized with a view to increase the selectivity, with respect to CPD, of efficient UV-induced (6-4) photoproduct formation. The deoxyribose residues of these analogs have been modified to increase north and south conformer populations at 5'- and 3'-ends, respectively. Dinucleotides whose 5'-end north population exceeds ca. 60% and whose 3'-end population is almost completely south display a three-fold selective enhancement in (6-4) adduct production when exposed to UV radiation, compared to TpT. These experimental results undoubtedly provide robust foundations for studying the singular ground-state proreactive species involved in the (6-4) photoproduct formation mechanism.

Isolation of new Paraburkholderia strains for polyhydroxybutyrate production.

Polyhydroxyalkanoates (PHAs) are bioplastics that can serve as substitutes for petroleum-based plastics with the advantages of being biodegradable, biocompatible, and biobased. The microbial production of polyhydroxyalkanoates is generally conducted in the presence of sugar mixes rich in monosaccharides. In this study, molecular and cultural approaches based on forest soils enriched with hydrocarbon complexes led to the identification and isolation of microbial strains affiliated with Paraburkholderia sp. that dominated the microbial communities that are recognized among the top polyhydroxyalkanoates producers. The genome sequencing of those isolated affiliated strains showed that compared to the reference type strain of their species, they harbored more gene copies of the enzymes involved in PHB synthesis. The microbial conversion of sugar mixes for the newly isolated strains showed a higher PHB production (g/L) and content (%) than was exhibited by the reference strain type of that genus Paraburkholderia for PHB production (P. sacchari LMG 19450T).

SN- and NS-puckered sugar conformers are precursors of the (6-4) photoproduct in thymine dinucleotide.

Some amount of furanose in a southern conformation, possibly in both, but certainly in one of the two adjacent nucleotides of a dipyrimidine site, is necessary for (6-4) photoproduct formation in oligonucleotides. To explore the necessity, role, and most favorable location of each South sugar conformer in the formation of the (6-4) adduct in the thymine dinucleotide TpT, the photochemical behavior of two synthetic analogues, in which the South sugar conformation is prohibited for one of their two sugars, has been examined. Herein, we experimentally demonstrate that the presence of one sugar presenting some amount of South puckering, at any of the extremities, is sufficient to trigger (6-4) adduct formation. Nonetheless, the photochemical behavior of the dinucleotide with a South-puckered conformation at the 5'-end, mimics more closely that of TpT. In addition, using the 5' North 3' South-dilocked dinucleotide, we demonstrate that the flexibility of the South pucker at the 3'-end has little influence on the (6-4) adduct formation.

The remarkable UV light invulnerability of thymine GNA dinucleotides.

We herein demonstrate the UV resistance of glycol nucleic acid (GNA) dinucleotides. This resistance sustains the hypothesis of GNA as a nucleic acid prebiotic ancestor on early Earth, a time of intense solar UV light. Such photorobustness, due to the absence of intrastrand base stacking, could offer an opportunity for nanodevice development requiring challenging UV conditions.

Small Molecule Mixture Analysis by Heteronuclear NMR under Spin Diffusion Conditions in Viscous DMSO-Water Solvent.

Spin diffusion in NMR occurs for small- and medium-sized molecules when their tumbling rate reduces in solution so that magnetization exchange by longitudinal cross relaxation becomes highly efficient. Composite DMSO-water viscous solvents were used for the first time to access the individual NMR spectra of a mixture components in spin diffusion conditions. The easy handling and high dissolution power of [D6 ]DMSO/H2 O offers a wide range of potential applications for polar and moderately apolar mixture analysis. In addition to 2D 1 H-1 H NOESY and 1 H-13 C HSQC-NOESY, 1 H-15 N HSQC-NOESY, 1D and 2D 1 H-19 F heteronuclear NOESY (HOESY) experiments were set up to offer new ways to individualize molecules within a mixture. This article reports the analysis of a polar mixture of four dipeptides dissolved in [D6 ]DMSO/H2 O (7:3 v/v) and that of a medium-polarity fluorinated dinucleotide dissolved in [D6 ]DMSO/H2 O (8:2 v/v) by means of spin diffusion in NOESY, HOESY, and HSQC-NOESY experiments.

A minute amount of s-puckered sugars is sufficient for (6-4) photoproduct formation at the dinucleotide level.

The di-2'-α-fluoro analogue of thymidylyl(3',5')thymidine, synthesized to probe the effect of a minimum amount of S conformer on the photoreactivity of dinucleotides, is endowed with only 3% and 8% of S sugar conformation at its 5'- and 3'-end, respectively. This analogue gives rise to the (6-4) photoproduct as efficiently as the dithymine dinucleotide (74% and 66% at the 5'- and 3'-end, respectively) under 254 nm. Our results suggest that the 5'-N, 3'-S conformer gives rise to the (6-4) photoproduct.

UV-induced TA photoproducts: formation and hydrolysis in double-stranded DNA.

Hydrolysis of TA photoproduct leads to two derivatives presenting different formation kinetic profiles depending on the oligomer content. The formation efficiency of TA photoproducts in UV-C-irradiated DNA slightly exceeds the formation of the trans,syn cyclobutane pyrimidine dimer at TT sites.