Domino reaction of a gold catalyzed 5-endo-dig cyclization and a [3,3]-sigmatropic rearrangement towards polysubstituted pyrazoles.

Pyrazoles are important heterocyclic compounds with a broad range of biological activities. A new procedure toward tri- or tetrasubstituted pyrazoles has been developed, via a one-pot gold catalyzed synthesis from hydrazines with alkynyl aldehydes or ketones. The reaction proceeds through consecutive hydrazone formation, 5-endo-dig cyclization and an aza-Claisen rearrangement resulting in the desired polysubstitued pyrazoles.

A chemoselective and continuous synthesis of m-sulfamoylbenzamide analogues.

For the synthesis of m-sulfamoylbenzamide analogues, small molecules which are known for their bioactivity, a chemoselective procedure has been developed starting from m-(chlorosulfonyl)benzoyl chloride. Although a chemoselective process in batch was already reported, a continuous-flow process reveals an increased selectivity at higher temperatures and without catalysts. In total, 15 analogues were synthesized, using similar conditions, with yields ranging between 65 and 99%. This is the first automated and chemoselective synthesis of m-sulfamoylbenzamide analogues.

Molecular priming as an approach to induce tolerance against abiotic and oxidative stresses in crop plants.

Abiotic stresses, including drought, salinity, extreme temperature, and pollutants, are the main cause of crop losses worldwide. Novel climate-adapted crops and stress tolerance-enhancing compounds are increasingly needed to counteract the negative effects of unfavorable stressful environments. A number of natural products and synthetic chemicals can protect model and crop plants against abiotic stresses through induction of molecular and physiological defense mechanisms, a process known as molecular priming. In addition to their stress-protective effect, some of these compounds can also stimulate plant growth. Here, we provide an overview of the known physiological and molecular mechanisms that induce molecular priming, together with a survey of the approaches aimed to discover and functionally study new stress-alleviating chemicals.

Chemical Genetics Approach Identifies Abnormal Inflorescence Meristem 1 as a Putative Target of a Novel Sulfonamide That Protects Catalase2-Deficient Arabidopsis against Photorespiratory Stress.

Alterations of hydrogen peroxide (H2O2) levels have a profound impact on numerous signaling cascades orchestrating plant growth, development, and stress signaling, including programmed cell death. To expand the repertoire of known molecular mechanisms implicated in H2O2 signaling, we performed a forward chemical screen to identify small molecules that could alleviate the photorespiratory-induced cell death phenotype of Arabidopsisthaliana mutants lacking H2O2-scavenging capacity by peroxisomal catalase2. Here, we report the characterization of pakerine, an m-sulfamoyl benzamide from the sulfonamide family. Pakerine alleviates the cell death phenotype of cat2 mutants exposed to photorespiration-promoting conditions and delays dark-induced senescence in wild-type Arabidopsis leaves. By using a combination of transcriptomics, metabolomics, and affinity purification, we identified abnormal inflorescence meristem 1 (AIM1) as a putative protein target of pakerine. AIM1 is a 3-hydroxyacyl-CoA dehydrogenase involved in fatty acid ß-oxidation that contributes to jasmonic acid (JA) and salicylic acid (SA) biosynthesis. Whereas intact JA biosynthesis was not required for pakerine bioactivity, our results point toward a role for ß-oxidation-dependent SA production in the execution of H2O2-mediated cell death.

Recent developments in antibacterial and antifungal chitosan and its derivatives.

Chitosan is the deacetylated form of chitin, a biopolymer that can be obtained from various waste streams and shows antimicrobial activity against different fungi, gram positive and gram negative bacteria. Although chitosan has been studied for years, many aspects remain unclear. This review gives an overview of the antimicrobial activity of chitosan and novel chitosan derivatives of the last 15 years. The most important parameters (molecular weight, degree of deacetylation, etc.) are discussed along with a status update on the mode of action of chitosan.

Petroselinic acid purification and its use for the fermentation of new sophorolipids.

Petroselinic acid, a positional isomer of oleic acid, was isolated from the vegetable oil of Coriandrum sativum fruits. This uncommon fatty acid was subsequently used as substrate for sophorolipid fermentation with a Starmerella bombicola lactone esterase overexpression (oe sble) strain. A petroselinic acid based diacetylated sophorolipid lactone was obtained in high purity without incorporation of de novo synthesized fatty acids such as oleic acid. A total production of 40 g/L was obtained. The petroselinic acid based sophorolipid lactone was subsequently hydrolyzed towards the petroselinic acid based sophorolipid acid. For both compounds, their critical micelle concentration (CMC) and corresponding surface tension were compared to their oleic acid based counterparts. Both petroselinic acid based sophorolipids displayed a much lower CMC value than their oleic acid based counterparts, although their minimal surface tension was the same. Besides, the sophorolipid fermentation product was chemically modified towards a novel C12 sophorolipid aldehyde. This derivative constitutes an interesting building block for further modification towards new-to-nature sophorolipids with high potential for self-assembly applications.

The influence of π-conjugated moieties on the thermodynamics of cooperatively self-assembling tricarboxamides.

A detailed investigation of the self-assembly behaviour of C3-symmetrical tricarboxamides reveals that a larger π-conjugated core does not increase the stability of assemblies in an apolar solvent but makes the system more sensitive to destabilization by addition of a good solvent.