A new total synthesis of porritoxin

A concise and efficient total synthesis of the phytotoxin porritoxin is described. The key step of the synthesis is based upon a Parham cyclization methodology which enables the creation of the lactam unit embedded in the title compound framework with the concomitant formation of the tethered hydroxyakyl chain.     

Highly Emissive Nanostructured Thin Films of Organic Host–Guests for Energy Conversion

All‐organic nanostructured host–guest materials (see picture) show enhanced, tunable fluorescence due to a high concentration of dyes with controlled spatial and geometrical organization that allows controlled resonant energy transfer. Homogeneous films of deoxycholic acid host–guests, provide coatings that convert near‐UV light into blue light with an efficiency higher than that of the standard polymeric blends.

     

A note on utility based pricing and asymptotic risk diversification

In principle, liabilities combining both insurancial risks (e.g. mortality/longevity, crop yield,...) and pure financial risks cannot be priced neither by applying the usual actuarial principles of diversification, nor by arbitrage-free replication arguments. Still, it has been often proposed in the literature to combine these two approaches by suggesting to hedge a pure financial payoff computed by taking the mean under the historical/objective probability measure on the part of the risk that can be diversified. Not surprisingly, simple examples show that this approach is typically inconsistent for risk adverse agents. We show that it can nevertheless be recovered asymptotically if we consider a sequence of agents whose absolute risk aversions go to zero and if the number of sold claims goes to infinity simultaneously. This follows from a general convergence result on utility indifference prices which is valid for both complete and incomplete financial markets. In particular, if the underlying financial market is complete, the limit price corresponds to the hedging cost of the mean payoff. If the financial market is incomplete but the agents behave asymptotically as exponential utility maximizers with vanishing risk aversion, we show that the utility indifference price converges to the expectation of the discounted payoff under the minimal entropy martingale measure.     

Synthesis and evaluation of new phosphonated δ-lactam and glutarimide derivatives as angiotensin converting enzyme inhibitors

An efficient synthesis of new γ,δ-insaturated δ-lactam and glutarimide derivatives bearing a phosphonomethyl group from a common allylphosphonate precursor is described. Our approach is based on a two-step procedure involving the preparation of phosphonated-1,5-ketoester and −1,5-diester followed by an amidation–heterocyclization sequence. The first step proceeds via Michael's addition of ethyl acetoacetate and diethyl malonate on an allylphosphonate starting material. The second step consists of a base-promoted intramolecular amidation-cyclization sequence with primary amines, which accounts for the construction of δ-lactams and glutarimide skeletons. We performed the evaluation of angiotensin I-converting enzyme (ACE) inhibition using an in vitro enzyme assay on six new compounds. Five compounds showed potent ACE inhibitory activity, with IC₅₀ values ranging from 0.02 to 0.27 mg/ml. Compared with Captopril, used as a reference drug, two new glutarimide derivatives exhibited higher efficiency ACE inhibition activity.     

Can Propagation Reaction in Carbocationic Polymerization and Copolymerization of Styrene be Diffusion Controlled ?

Summary: The reactivity ratios r₁ and r₂ in copolymerizations of styrene and parasubstituted styrenes, for which r₁ = 1/r₂, are in contradiction with diffusion control for their propagation reactions. The cross propagation rate constants k_12copol in copolymerization of styrene with p-chlorostyrene, p-methylstyrene and p-methoxystyrene have been shown to increase with their nucleophilicity parameter N. This is also not compatible with diffusion controlled cross propagation and propagation, but agrees with similar rate constants of propagation for these monomers. The capping rate constants k_12capp of reactions of poly(p-methylstyrene)^± and poly(p-methoxystyrene)^± with π-nucleophiles also increase with N, but with a much larger selectivity. This shows that k_12copol and k_12capp are not identical. The k, from 10⁹ to 6 10⁹ L mol⁻¹ s⁻¹, obtained with p-chlorostyrene, styrene and p-methylstyrene by the Diffusion Clock (DC) method are not consistent with those derived from the ionic species concentration (ISC method) for indene, 2,4,6-trimethylstyrene and p-methoxystyrene of the order of 10⁴ – 10⁵ L mol⁻¹ s⁻¹, also measured for living polymerization. These last values are in agreement with those measured previously in nonliving systems, and with an approximate compensation between the reactivity of a monomer and that of the corresponding carbocation.     

A regularized nonnegative canonical polyadic decomposition algorithm with preprocessing for 3D fluorescence spectroscopy

We consider blind source separation in chemical analysis focussing on the 3D fluorescence spectroscopy framework. We present an alternative method to process the Fluorescence Excitation‐Emission Matrices (FEEM): first, a preprocessing is applied to eliminate the Raman and Rayleigh scattering peaks that clutter the FEEM. To improve its robustness versus possible improper settings, we suggest to associate the classical Zepp's method with a morphological image filtering technique. Then, in the second stage, the Canonical Polyadic (CP or Candecomp/Parafac) decomposition of a nonnegative three‐way array has to be computed. In the fluorescence spectroscopy context, the constituent vectors of the loading matrices should be nonnegative (since standing for spectra and concentrations). Thus, we suggest a new nonnegative third order CP decomposition algorithm (NNCP) based on a nonlinear conjugate gradient optimization algorithm with regularization terms and periodic restarts. Computer simulations performed on real experimental data are provided to enlighten the effectiveness and robustness of the whole processing chain and to validate the approach. Copyright © 2015 John Wiley & Sons, Ltd.     

About propagation rate constants in carbocationic polymerizations

Published carbocationic propagation rate constants vary between 2 10³ and 5 10⁹ L·mol⁻¹·s⁻¹, e.g. for k_p^± with styrene in CH₂Cl₂. The low values were deduced from an evaluation of [P_n^±], the high values from competitive experiments assuming diffusion-controlled termination. Recent kinetic and spectrophotometric studies of indene living polymerization have given intermediate values (5 10⁴ to 5 10⁵ L·mol⁻¹·sec⁻¹). An explanation of the high values obtained by the competition method is suggested.