Synthesis of enantiopure C3- and C4-hydroxyretinals and their enzymatic reduction by ADH8 from Xenopus laevis

(R)-all-trans-3-hydroxyretinal 1, (S)-all-trans-4-hydroxyretinal and (R)-all-trans-4-hydroxyretinal have been synthesized stereoselectively by Horner-Wadsworth-Emmons and Stille cross-coupling as bond-forming reactions. The CBS method of ketone reduction was used in the enantioface-differentiation step to provide the precursors for the synthesis of the 4-hydroxyretinal enantiomers. The kinetic constants of Xenopus laevis ADH8 with these retinoids have been determined.     

Cyclic AMP and low molecular weight effector(s) present in yeast extract are involved in pectin lyase production by Penicillium griseoroseum cultured on sucrose

Pectin lyase (PL) induction by organic and inorganic components of yeast extract (YE) was evaluated in Penicillium griseoroseum, cultured in a mineral medium containing sucrose, by determining PL activity (A235) and mycelial growth (mycelial dry weight). The lowest YE concentration that promoted significant PL induction without acting as a carbon source for the fungus corresponded to 0.0075%. Neither calcined YE nor a nutrient solution containing micronutrients induced PL production, indicating that the inducer was an organic compound. Vitamins, phospholipid components, amino acids, and nitrogenous bases were tested in place of YE and promoted no significant PL induction. A PL inducer compound was found to be soluble in the nucleotide fraction obtained during extraction of YE. The inducer was shown to be a thermostable polar substance dialyzable at 2000 Daltons, hydrolyzable by HCl, and activated by boiling for up to 60 min. Cyclic AMP (cAMP) exogenously added to the culture medium at 5 and 10 mM was capable of inducing PL in P. griseoroseum grown on sucrose, suggesting that at least one compound may be present in YE acting in a cooperative fashion for the maintenance of high levels of cAMP into the cell. PL activity and the level of cAMP inside the fungal cells increased after the addition of YE to the culture medium, suggesting the participation of this messenger in this enzyme's synthesis.     

High 1,5-anti stereoinduction in boron-mediated aldol reactions of methyl ketones

[reaction: see text] We report herein a very efficient and synthetically useful 1,4-anti-1,5-anti boron-mediated aldol reaction of a chiral alpha-methyl-beta-alkoxy methyl ketone with achiral aldehydes.     

Total synthesis of nahuoic acid A via a putative biogenetic intramolecular Diels–Alder (IMDA) reaction

Inspired by the biogenetic proposal of an intramolecular Diels–Alder (IMDA) cycloaddition, the total synthesis of natural product nahuoic acid A, a cofactor-competitive inhibitor of the epigenetic enzyme lysine methyl transferase SETD8, has been carried out. A non-conjugated pentaenal precursor was synthesized with high levels of stereoselectivity at seven stereogenic centers and with the appropriate control of double bond geometries. Although the IMDA reaction of the non-conjugated pentaenal using Me₂AlCl for catalysis at −40 °C selectively afforded the trans-fused diastereomer corresponding to the Re-endo mode of cycloaddition, under thermal reaction conditions it gave rise to a mixture of diastereomers, that preferentially formed through the exo mode, including the cis-fused angularly-methylated octahydronaphthalene diastereomer precursor of nahuoic acid A. The natural product could be obtained upon oxidation and overall deprotection of the hydroxyl groups present in the Si-exo IMDA diastereomer.

The total synthesis of natural product nahuoic acid A, a cofactor-competitive inhibitor of the epigenetic enzyme lysine methyl transferase SETD8, has been carried out based on the biogenetic proposal of an intramolecular Diels–Alder (IMDA) cycloaddition.     

Periodic boundary value problems for impulsive fuzzy differential equations

The peculiarity of the Hukuhara derivative makes it impossible to find periodic solutions for fuzzy differential equations with the exception of very restrictive situations. In this work, we consider a boundary value problem associated with an impulsive fuzzy differential equation and approximate the extremal solutions in a fuzzy functional interval using the monotone method. Fuzzy comparison results are useful in our procedure and the expression of the solution for some impulsive periodic ‘linear’ differential problems is also provided.     

4′-(2-(2-Ethoxyethoxy)ethoxy)biphenyl-4-carboxylic acid—a polar smectogen for amphipathic liquid crystals

We describe a new calamitic smectogen and some of its esters with a three-block molecular architecture (polar oxyethylene chain, rigid biphenyl and non-polar aliphatic chain) which were characterised by a combination of optical, thermical, X-ray and computational techniques. The title compound is a valuable smectogenic building block for amphipathic functional organic materials.     

Fabrication of rubrene nanowires on vicinal (0 0 0 1) sapphire surfaces

Morphology of high-vacuum deposited rubrene thin films on the annealed (0 0 0 1) vicinal sapphire surfaces was studied by atomic force microscopy in non-contact mode. Atomic force microscopy images of rubrene thin films indicate that a regular array of steps on the sapphire surface acts as a template for the growth of the arrays of rubrene nanosize wires. To further demonstrate that morphological features of a substrate are crucial in determining the morphology of rubrene layers we have grown rubrene on the sapphire surfaces that were characterized by the terrace-and-step morphology with islands. We have found preferential nucleation of rubrene molecules at the intersection between a terrace and a step, as well as around the islands located on terraces.     

NiCl2-catalyzed hydrophosphinylation

[reaction: see text] A new nickel-based catalytic system has been developed for phosphorus-carbon bond formation. The addition of alkyl phosphinates to alkynes is catalyzed by nickel chloride in the absence of added ligand. The reaction generally proceeds in high yields, even with internal alkynes, which were poor substrates in our previously reported palladium-catalyzed hydrophosphinylation of alkyl phosphinates. The method is useful for the preparation of H-phosphinate esters and their derivatives. The one-pot synthesis of various important organophosphorus compounds is also demonstrated. The reaction can be conducted with microwave heating.     

Effect of dehydration on photoinduced transformation in gelatin films made with 14-fluoro bacteriorhodopsin derivatives

Photoinduced transformation in gelatin films made with 14-fluoro bacteriorhodopsin derivatives, both wild-type (WT) and D96N mutant, were studied. Spectral and kinetic peculiarities for these two types of samples were compared over a wide range of relative humidity (9–92%). Analysis of the results considered two existing photoinduced processes that occur in suspensions and films of corresponding pigments. It was demonstrated that there is a range of humidity in which the performance of fluorine WT bacteriorhodopsin gelatin films may offer a technological advantage compared with fluorine D96N bacteriorhodopsin.