One-dimensional order in atactic polyacrylates containing aromatic side groups

To help in the understanding of the relations between chemical structure and morphological order in polymers of the type of poly(p-biphenyl acrylate) (PPBA), some polymers of similar structure have been synthesized and some of their physical properties studied. These polymers are: poly(p-biphenyl methacrylate), poly(vinyl p-phenyl benzoate), poly(p-phenyl benzyl acrylate), poly(p-benzyl phenyl acrylate) and poly(p-cyclohexyl phenyl acrylate) (PPCPA). Only PPCPA has been shown to possess a one-dimensional order in the solid state for reasons which are briefly discussed.The effect of copolymerization on the structural order of PPBA has also been given preliminary study. Copolymers of p-biphenyl acrylate (PBA) with p-biphenyl methacrylate (PBMA), N-vinyl carbazole (NVC) and p-cyclohexyl phenyl acrylate (PCPA) have been prepared and their properties have been studied by DSC and X-ray techniques. Small concentrations of PBMA or NVC units are sufficient to cancel the order of PPBA. On the contrary, copolymers of PBA and PCPA of any composition display morphological order in the solid state.     

A binary algorithm with low divergence for modular inversion on SIMD architectures

When performing modular arithmetic the most computationally expensive operation is the modular inversion of an integer. Its cost might be a problem for cryptanalytical applications (like the transformation from projective to affine coordinates within a Pollard rho algorithm implementation to solve the discrete logarithm problem on an elliptic curve) where performances constitute a key aspect. Good platforms for such operations are single-instruction multiple-data architectures, like graphic processing units (GPUs) because of their extremely competitive performance/price ratio. Unfortunately, when a single thread computes a single inversion, the whole computation on GPUs can be significantly slowed down in the presence of divergent threads. In this paper we describe a new algorithm to compute modular inversion on GPUs based on Stein’s Binary GCD. By exploiting the De Bruijn sequences and the Montgomery arithmetic, our version of Stein’s algorithm better fits GPUs, since it reduces the divergence among threads of the original algorithm. The paper includes a brief report on tests of our algorithm in six prime fields with characteristics of size ranging from 109 to 359 bits and in the two prime fields associated to the Mersenne primes \(2^{521} - 1\) and \(2^{607} - 1\).     

Multitarget Drug Discovery for Alzheimer's Disease: Triazinones as BACE‐1 and GSK‐3β Inhibitors

Cumulative evidence strongly supports that the amyloid and tau hypotheses are not mutually exclusive, but concomitantly contribute to neurodegeneration in Alzheimer′s disease (AD). Thus, the development of multitarget drugs which are involved in both pathways might represent a promising therapeutic strategy. Accordingly, reported here in is the discovery of 6‐amino‐4‐phenyl‐3,4‐dihydro‐1,3,5‐triazin‐2(1H)‐ones as the first class of molecules able to simultaneously modulate BACE‐1 and GSK‐3β. Notably, one triazinone showed well‐balanced in vitro potencies against the two enzymes (IC₅₀ of (18.03±0.01) μM and (14.67±0.78) μM for BACE‐1 and GSK‐3β, respectively). In cell‐based assays, it displayed effective neuroprotective and neurogenic activities and no neurotoxicity. It also showed good brain permeability in a preliminary pharmacokinetic assessment in mice. Overall, triazinones might represent a promising starting point towards high quality lead compounds with an AD‐modifying potential.     

Glass transition temperatures of some linear polymers containing phenyl side groups

The glass transition temperatures of a number of poly(vinyl phenyl ketones), poly-(vinyl benzoates), and poly(phenyl acrylates) have been measured by a refractometric method. The effects exerted on T_g by the nature and position of the ring substituents and by the different groups binding the pendant phenyl rings to the polyvinyl chain are discussed. The importance of knowledge of the side-group motions in the glassy state for the interpretation of glass temperature data is emphasized.     

Domino Knoevenagel/Diels-Alder sequence coupled to Suzuki reaction: a valuable synthetic platform for chemical biology

A small library of peculiar biphenyl and terphenyl-containing spirocyclic triones has been synthesized in parallel by combining the organocatalytic three-component domino Knoevenagel/Diels-Alder sequence to Suzuki coupling. This methodology is fast, general and serves as a platform to gain access to novel chemical tools to probe protein-protein interactions.     

Macrocycloadditions leading to conformationally restricted small molecules

[reaction: see text] The Cu(I)-catalyzed cycloaddition of alkynes and azides (click reaction) provides a robust method for the construction of macrocyclic small molecules via an intramolecular macrocycloaddition. A three-subunit system has been used to explore the tolerance of this macrocycloaddition to variations of stereochemistries and substituents.     

Some aspects of the n-vinylcarbazole polymerization initiated by iodine

The polymerization of N-vinylcarbazole initiated by iodine in dichloroethane solution, shows some interesting features, particularly the unusual trend of the conversion-time curves: in all cases a very fast initial reaction is followed by a much slower process. Molecular weights of the polymers decrease noticeably with increasing conversion and with increasing initial monomer concentration. The system is very complex and the data indicate that two different mechanisms are operating.     

Antioxidant activity of hydroxystilbene derivatives in homogeneous solution

The antioxidant activity of the cis and trans isomers of several analogues of resveratrol and pterostilbene has been investigated, especially with regard to the effect of the stereochemistry about the olefinic double bond. The antioxidant power of these compounds was estimated by measuring the rate constants for their reactions with peroxyl radicals and, with two of them, the bond dissociation enthalpy (BDE) of the phenolic O-H bond which is cleaved in the inhibition reaction. The present data show that in homogeneous solution the various hydroxystilbenes investigated behave as mild antioxidants with the notable exceptions of the trans isomer of 4 and 6, whose activities are only slightly lower than that of alpha-tocopherol (vitamin E). The rate constants of the inhibition reaction show that the antioxidant activity of the cis-hydroxystilbene is in all the examined cases worse, by a factor ranging between 2 and 6, than that of the corresponding trans isomers. This lower reactivity depends on enthalpy factors as it can be inferred by the experimental values of the O-H bond dissociation enthalpy in the two geometric isomers of 3',5'-di-tert-butyl-4'-hydroxy-3,5-dimethoxystilbene showing that the strength of the O-H bond in the cis isomer is larger by 1.8 kcal/mol. DFT calculations provide a rationalization of this result, indicating that, although the cis geometry implies a destabilization with respect to the trans species of both phenoxyl radical and parent hydroxystilbene, the destabilization of the radical is larger because the folding of the structure strongly reduces the delocalization of the unpaired electron on the styryl group. A comparison of these results with previously reported data on the proapoptotic activity of these stilbenoids suggests that these two properties are not correlated.