Synthesis and biological evaluation of cycloalkylidene carboxylic acids as novel effectors of Ras/Raf interaction

Chemometric analysis of Tunisian durum wheat metabolites using UPLC-ESI-QTOF-MS/MS

Bioactive compounds in wheat have received a great interest in the last few years due to their nutritional and health benefits. Various analytical procedures were used to identify these compounds in wheat kernels. An ultra-performance liquid chromatography coupled to electrospray ionization quadrupole-time-of-flight mass spectrometry (UPLC-ESI-QTOF-MS/MS) was used for the screening of bioactive compounds in seven Tunisian durum wheat extracts. The aim of this study was to realize a screening of several classes of bioactive compounds in the same analysis and to identify specific metabolite markers for discriminating the durum wheat varieties. The UPLC-ESI-QTOF-MS/MS allows the detection of 81 metabolites, belonging to different chemical families such as sugars, organic acids, amino acids, fatty acids, and phenolic compounds represented by benzoic and cinnamic acid derivatives, phenolic alcohols, flavones, lignans, and condensed tannins. Chemical profiles identified varied greatly between different wheat genotypes. As far as the authors know, this is the first time that different chemical classes were detected at the same time in durum wheat kernels using UPLC-ESI-QTOF-MS/MS. This study gives the most complete map of metabolites in Tunisian durum wheat and proves that UPLC-QTOF-MS/MS coupled with chemometric analysis is a great tool for discrimination between durum wheat cultivars.

Structure-activity relationships of new cyanothiophene inhibitors of the essential peptidoglycan biosynthesis enzyme MurF

Peptidoglycan is an essential component of the bacterial cell wall, and enzymes involved in its biosynthesis represent validated targets for antibacterial drug discovery. MurF catalyzes the final intracellular peptidoglycan biosynthesis step: the addition of D-Ala-D-Ala to the nucleotide precursor UDP-MurNAc-L-Ala-γ-D-Glu-meso-DAP (or L-Lys). As MurF has no human counterpart, it represents an attractive target for the development of new antibacterial drugs. Using recently published cyanothiophene inhibitors of MurF from Streptococcus pneumoniae as a starting point, we designed and synthesized a series of structurally related derivatives and investigated their inhibition of MurF enzymes from different bacterial species. Systematic structural modifications of the parent compounds resulted in a series of nanomolar inhibitors of MurF from S. pneumoniae and micromolar inhibitors of MurF from Escherichia coli and Staphylococcus aureus. Some of the inhibitors also show antibacterial activity against S. pneumoniae R6. These findings, together with two new co-crystal structures, represent an excellent starting point for further optimization toward effective novel antibacterials.

Two-carbon homologation of aldehydes and ketones to α,β-unsaturated aldehydes

Phosphonate reagents were developed for the two-carbon homologation of aldehydes or ketones to unbranched- or methyl-branched α,β-unsaturated aldehydes. The phosphonate reagents, diethyl methylformyl-2-phosphonate dimethylhydrazone and diethyl ethylformyl-2-phosphonate dimethylhydrazone, contained a protected aldehyde group instead of the usual ester group. A homologation cycle entailed condensation of the reagent with the starting aldehyde, followed by removal of the dimethylhydrazone protective group with a biphasic mixture of 1 M HCl and petroleum ether. This robust two-step process worked with a variety of aldehydes and ketones. Overall isolated yields of unsaturated aldehyde products ranged from 71% to 86% after the condensation and deprotection steps.

Methyl Substituents at the 11 or 12 Position of Retinal Profoundly and Differentially Affect Photochemistry and Signalling Activity of Rhodopsin

The C-11=C-12 double bond of the retinylidene chromophore of rhodopsin holds a central position in its light-induced photoisomerization and hence the photosensory function of this visual pigment. To probe the local environment of the HC-11=C-12H element we have prepared the 11-methyl and 12-methyl derivatives of 11-Z retinal and incorporated these into opsin to generate the rhodopsin analogs 11-methyl and 12-methyl rhodopsin. These analog pigments form with much slower kinetics and lower efficiency than the native pigment. The initial photochemistry and the signaling activity of the analog pigments were investigated by UV-vis and FTIR spectroscopy, and by a G protein activation assay. Our data indicate that the ultrafast formation of the first photointermediate is strongly perturbed by the presence of an 11-methyl substituent, but much less by a 12-methyl substituent. These results support the current concept of the mechanism of the primary photoisomerization event in rhodopsin. An important stronghold of this concept is an out-of-plane movement of the C-12H element, which is facilitated by torsion as well as extended positive charge delocalization into the C-10-C-13 segment of the chromophore. We argue that this mechanism is maintained principally with a methyl substituent at C-12. In addition, we show that both an 11-methyl and a 12-methyl substitutent perturb the photointermediate cascade and finally yield a low-activity state of the receptor. The 11-methyl pigment retains about 30% of the G protein activation rate of native rhodopsin, while the 12-methyl chromophore behaves like an inverse agonist up to at least 20 degrees C, trapping the protein in a perturbed Meta-I-like conformation. We conclude that the isomerization region of the chromophore and the spatial structure of the binding site are finely tuned, in order to achieve a high photosensory potential with an efficient pathway to a high-activity state.

Ras/Raf signalling and emerging pharmacotherapeutic targets

The Ras-Raf-MEK-ERK pathway is a ubiquitously expressed signalling module that regulates the proliferation, differentiation and survival of cells. This pathway features several oncogenes and is deregulated in approximately 30% of all human cancers. Thus, it has emerged as a prime target for antitumour therapy. Drugs targeting Ras, Raf or MEK are currently in clinical trials. They comprise vaccines, isoprenylation inhibitors, antisense compounds and kinase inhibitors. Most are remarkably well tolerated and some show promising efficacy. However, it is not clear which components of this pathway should be targeted and how maximum efficacy can be achieved. This paper reviews the current efforts with an emphasis on new mechanistic and conceptual approaches.