Automated densimetric system: Measurements and uncertainties for compressed fluids

In this work, we present the automatization of a densimetric system for pVT measurements of compressed fluids, operating over the temperature range from 283.15 K to 398.15 K and pressures up to 70 MPa. The heart of the automatic assembly is a commercial Anton Paar DMA HPM vibrating-tube densimeter. The densimeter was calibrated using the method developed by Lagourette et al. and modified recently by Comuñas et al. The fluids used in this calibration were a vacuum, water, and n-decane. Data reliability has been verified by comparing our experimental results for toluene with literature data. The uncertainty of the experimental density was evaluated following the rigorous procedure of the EA-4/02 guide. Moreover, new density measurements of pentaerythritol tetrapentanoate ester are presented. For this fluid with significant viscosity values, a correction factor was applied to take into account the damping effects in the densimeter cell.     

New derivatives of dibenzo[b,e][1,4]diazepin‐1‐ones by an efficient synthesis and spectroscopy

An efficient synthesis of four steps to obtain twelve new derivatives of 3,3‐dimethyl‐2,3,4,5,10,11‐hexahydro‐8‐[(o‐; and p‐methoxy)phenoxy]‐11‐[(o‐; and p‐R)phenyl]‐1H‐dibenzo[b,e][1,4]diazepin‐1‐ones IV, 1‐12 with possible biological and pharmacological activity as anticonvulsant and schizophrenia treatment in the central nervous system (CNS). The final products were obtained by condensation and cyclization between 3‐{4‐[(o‐; and p‐methoxy)phenoxy]‐1,2‐phenylenediamine}‐5,5‐dimethyl‐2‐cyclohexenone with (o‐; and p‐R)benzaldehyde. The structure of all products was corroborated by spectroscopy of ir, ¹H‐nmr, ¹³C‐nmr, with bidimensional experiments and MS in Low and high resolution with Collision‐Induced Dissociation experiments (CID).     

Some modular relations for the Göllnitz-Gordon functions and Ramanujan’s modular equations

Huang used the methods of Rogers, Watson and Bressoud to derive some new modular relations involving the Göllnitz-Gordon functions. In this paper, using Ramanujan’s modular equations, we present a uniform method to prove these modular relations established by Huang.     

Ipso-chlorosulfonylation of calixarenes: a powerful tool for the selective functionalization of the large rim

In our quest for the elaboration of supramolecular models of metallo-enzyme active sites, we became interested in developing new methodologies for the selective functionalization of the large rim of calix[6]arenes. Here, we describe a novel reaction, i.e. the ipso-chlorosulfonylation of calixarene derivatives. The process has been found to be highly efficient, selective and versatile. The regioselectivity is controlled by the nature of the O-substituents at the small rim. Indeed, when O-alkylated by a protonable imidazole group, the aromatic rings are deactivated toward an electrophilic attack and the anisol units can be selectively ipso-chlorosulfonylated under mild conditions (rt). Performing the reaction at a higher temperature allowed the per-chlorosulfonylation to take place. Hence, the synthesis of various sulfonate and sulfonamide derivatives is reported. Finally, a combination of ipso-nitration and chlorosulfonylation allows the per-functionalization of the aromatic units at the large rim in selective alternate positions. Overall, this novel methodology opens new routes to a variety of calixarenes, allowing the tuning of their physical properties without drastically altering their hydrophobic conic cavities.     

Directional Control and Supramolecular Protection Allowing the Chemo‐ and Regioselective Transformation of a Triamine

A Zn^II‐funnel complex based on a calix[6]arene ligand decorated with three tris(imidazolyl) arms at one end of the cone and three NH₂ substituents at the other end, acts as a multipoint recognition host for polyfunctionalized guests. The selectivity is ensured by coordination to Zn^II, CH–π interaction within the calix cone, and H‐bonding at both rims of the cavity. As a result of these multiple interactions, the host can wrap and orient an unsymmetrical triamine guest with a high selectivity. Furthermore, a proton‐monitored switch between the regio‐isomeric adducts allows reversible inversion of the directionality of the system. Thanks to this directional control, the regioselective mono‐carbamoylation of the unsymmetrical triamine guest was successfully achieved on a preparative scale. This case study shows that a funnel‐like receptor can be used as a supramolecular protecting tool allowing a transformation which would be impracticable with conventional covalent chemistry.     

First triazole-linked porphyrin-fullerene dyads

A general procedure for the synthesis of 1,2,3-triazole-linked porphyrin-fullerene dyads is described. Four of these compounds have been prepared and characterized.     

Stability of recombinant green fluorescent protein (GFPuv) in glucose solutions at different concentrations and pH values

The stability at room temperature (25°C) of recombinant green fluorescent protein (GFPuv), expressed by Escherichia coli cells and isolated by three-phase partitioning extraction with hydrophobic interaction column, was studied. The GFPuv was diluted in buffered (each 10 mM: Tris-HCl, pH 8.0; phosphate, pH 6.0 and 7.0 and acetate, pH 5.0) and in unbuffered (water for injection [WFI]; pH 6.70 ± 0.40) glucose solutions (from 1.5 to 50%). By assaying the loss of fluorescence intensity as a measure of denaturation, the stability of GFPuv in these solutions was evaluated relative to glucose concentration, pH, osmolarity, density, conductivity, and viscosity. The extent of protein denaturation (loss of fluorescence intensity) was expressed in decimal reduction time (D-value), the time required to reduce 90% of the initial fluorescence intensity of GFPuv. The D-value between 56 and 83 h of GFPuv at 1.5–15% glucose in WFI was equivalent to 20–30% glucose in a phosphate. The stability of GFPuv in 50% glucose was similar for all buffers studied and four times higher than in WFI. By the convenient measure of fluorescence intensity, GFPuv can be used as an indicator to report the extent of denaturation rates of other proteins in glucose solutions.