Quantitative 1 H NMR spectroscopy (qNMR) in the early process development of a new quorum sensing inhibitor.

2-methyl-5,6,7,8-tetrahydro-2H-chromen-4(3H)-one (called 6-oxo) is presented as a new AI-1 quorum sensing inhibitor for Vibrio harveyi. The development of a chemical process to afford traceable materials for new biological assays demands the development of analytical methods to ensure their purity and quality. This work describes the use of quantitative 1 H nuclear magnetic resonance (NMR) spectroscopy (qNMR) to assess the purity of a sample of 6-oxo (99.88%) and a sample of its major process impurity (E)-1-(2-hydroxycyclohex-2-en-1-yl)but-2-en-1-one (called HCB; 98.28%). To explore the scope of the use of qNMR to quantify the amount of low-content components in samples related to the chemical process for 6-oxo synthesis, this work also determined the amount of 6-oxo in two HCB samples: (a) the high-purity HCB sample described above and (b) a crude HCB sample collected during the chemical process. Despite the complexity of the crude sample, the amount of 6-oxo was readily assessed and could help to estimate the extent to which 6-oxo was already formed during the HCB synthesis. This information can help the understanding of how the process parameters can be modified to improve the performance of the whole process, by controlling the reaction mechanisms working at each step of this chemical process. In this context, our results reinforce qNMR as a complementary analytical tool for the quantification of the main component found in a sample, contributing to the standardization of reference materials and thus allowing the development of analytical methods for process control and traceability of the samples used for biological assays.

Synthesis of novel sulfide-based cyclic peptidomimetic analogues to solonamides.

Eight new sulfide-based cyclic peptidomimetic analogues of solonamides A and B have been synthesized via solid-phase peptide synthesis and SN2' reaction on a Morita-Baylis-Hillman (MBH) residue introduced at the N-terminal of a tetrapeptide. This last step takes advantage of the electrophilic feature of the MBH residue and represents a new cyclization strategy occurring. The analogues were prepared in moderate overall yields and did not show toxic effects on Staphylococcus aureus growth and were not toxic to human fibroblasts. Two of them inhibited the hemolytic activity of S. aureus, suggesting an interfering action in the bacterial quorum sensing similar to the one already reported for solonamides.

"Dba-free" palladium intermediates of the Heck-Matsuda reaction.

The "dba-free" Heck-Matsuda reaction was investigated via direct ESI-MS(/MS) monitoring. Palladium species involved in the reduction of Pd(II) during a Wacker type reaction and several "dba-free" arylpalladium transient complexes were detected and characterized. Based on these findings, a more comprehensible catalytic cycle for this pivotal reaction is suggested.

Development and validation of analytical method for identification of new psychoactive substances using linear retention indexes and gas chromatography-mass spectrometry.

New Psychoactive Substances (NPS) are quickly developing to evade legislation, posing unprecedented challenges to public health and law enforcement authorities around the world. The aim of this work was to develop and validate a simple and reliable non-target gas chromatography/mass spectrometry (GC/MS) analytical method based on linear retention indexes for the expeditious identification of NPS without the need of analytical standards. The method was optimized and validated for 22 different drugs covering ten categories: phenethylamines (amphetamine, MDMA, methamphetamine, 25CNBOMe, 2-FA, 5-MAPB), "classic" drugs (cocaine, ephedrine, THC, heroine), synthetic cannabinoids (JWH-081, AM-2201, JWH-210, MAM-2201), piperazines (o-CPP, p-CPP), tryptamines (5-MeO-MiPT), synthetic cathinones (N-ethylpentylone), synthetic opioids (U-47700), aminoindanes (5-IAI), plant-based substances (Salvinorin-A) and "other" (methiopropamine). Three figures of merit (Selectivity, Precision and Robustness) were evaluated with retention index confidence intervals ranging from 0.5 to 20.6 i.u. and relative standard deviations in the range of 0.003% to 0.027% (repeatability) and 0.02% to 0.29% (intermediate precision). A general equation for estimating linear retention index variation as a function of retention time tolerance has been derived. This result in combination with a 2III6-3 fractional factorial design allowed to conclude column polarity to be only statistically relevant factor as compared to gas flow, split ratio, injection temperature, temperature program offset and column brand.

(1R,2S,5R)-5-Methyl-2-[2-(4-nitro-phen-yl)propan-2-yl]cyclo-hexyl 2-(4-meth-oxy-phen-yl)-2,5-di-hydro-1H-pyrrole-1-carboxyl-ate: crystal structure and Hirshfeld analysis.

In the title compound, C28H34N2O5, the adjacent ester and nitro-benzene substituents are connected via an intra-molecular methyl-ene-C-H⋯π(nitrobenzene) inter-action and the mol-ecule approximates to a U-shape. The di-hydro-pyrrole ring (r.m.s. deviation = 0.003 Å) is almost co-planar with the carboxyl-ate residue [Cm-N-C1-Oc (m = methine, c = carbox-yl) torsion angle = 1.8 (4)°] but is orthogonal to the 4-meth-oxy-benzene ring [dihedral angle = 84.34 (17)°]. In the crystal, methyl-ene-C-H⋯O(carbon-yl) inter-actions lead to linear supra-molecular chains along the b-axis direction, which pack without directional inter-actions between them. The analysis of the calculated Hirshfeld surface points to the importance of weak inter-atomic H⋯H, O⋯H/H⋯O and C⋯H/H⋯C contacts in the crystal.

Exogenous nucleosome-binding molecules: a potential new class of therapeutic drugs.

Constant changes in the structure of chromatin regulate gene expression. Molecules that bind to the nucleosome, the complex of DNA and histone proteins, are key modulators of chromatin structure. Conceptually, the nucleosome was first identified as a therapeutic target 14 years ago, when small molecules started to be elegantly designed for nucleosomal DNA binding. Concomitantly, emergent drugs that target enzymes that affect chromatin structure have been developed to a treat myriad of diseases, such as cancer. Here, we discuss the development of more complex molecules, such as peptides and peptidomimetics, to directly target the nucleosome surface to modulate chromatin structure. This new strategy presents great challenges that need to be overcome to develop the exogenous nucleosome-binding molecules (eNBMs) as therapeutic agents.