Stereodivergent Synthesis of (+)- and (−)-Isolineatin

A stereodivergent approach to (+)- and (−)-isolineatin using (<i>S</i>)-4-methyl-5-pivaloyloxymethyl-2­(5<i>H</i>)-furanone as the single source of asymmetry by exploiting the inherent chirality at the C-5 stereocenter is described

Flexible Approach to <i>Stemona</i> Alkaloids: Total Syntheses of (−)-Stemospironine and Three New Diastereoisomeric Analogs

Total syntheses of (−)-stemospironine and three new diastereoisomeric analogs have been completed through a flexible strategy devised for <i>Stemona</i> alkaloids. The azabicycle <b>7</b> is the pivotal intermediate, from which the sequence splits according to each particular target. The most remarkable differential feature for stemospironine is the installation of the spiranic γ-lactone through an intramolecular Horner–Wadsworth–Emmons olefination. The configuration of the stereogenic center at C-11 was controlled by fine-tuning of the synthetic sequence

Intramolecular Photocycloaddition of 2(5<i>H</i>)‑Furanones to Temporarily Tethered Terminal Alkenes as a Stereoselective Source of Enantiomerically Pure Polyfunctionalyzed Cyclobutanes

Allyloxymethyloxymethyl and 4-pentenoyloxymethyl substituents have been used as tethering groups to study the intramolecular [2 + 2] photocycloaddition of chiral 5-substituted 2­(5<i>H</i>)-furanones. The photoreactions proceed in good yield and provide the expected regio- and diastereoselective tricyclic compounds with complementary regioselectivity, which depends on whether the vinyl chain is attached to the furanone by an acetal or an ester linkage. Computational simulations agree with experimental observations and indicate that the origin of the different observed regioselectivity in the intramolecular photochemical reaction of lactones <b>5</b> and <b>6</b> arises from the relative stability of the initial conformers. The synthetic potential of the enantiomerically pure photoadducts is illustrated by preparing an all-<i>cis</i> 1,2,3-trisubstituted cyclobutane bearing fully orthogonally protected hydroxyl groups

Intramolecular Photocycloaddition of 2(5<i>H</i>)‑Furanones to Temporarily Tethered Terminal Alkenes as a Stereoselective Source of Enantiomerically Pure Polyfunctionalyzed Cyclobutanes

Allyloxymethyloxymethyl and 4-pentenoyloxymethyl substituents have been used as tethering groups to study the intramolecular [2 + 2] photocycloaddition of chiral 5-substituted 2­(5<i>H</i>)-furanones. The photoreactions proceed in good yield and provide the expected regio- and diastereoselective tricyclic compounds with complementary regioselectivity, which depends on whether the vinyl chain is attached to the furanone by an acetal or an ester linkage. Computational simulations agree with experimental observations and indicate that the origin of the different observed regioselectivity in the intramolecular photochemical reaction of lactones <b>5</b> and <b>6</b> arises from the relative stability of the initial conformers. The synthetic potential of the enantiomerically pure photoadducts is illustrated by preparing an all-<i>cis</i> 1,2,3-trisubstituted cyclobutane bearing fully orthogonally protected hydroxyl groups

A comparison of two complete feed blocks based on sorghum stover of two different cultivars on weight gain in sheep and economy of feeding

The effect of different sorghum stover fodder quality in densified total mixed ration (DTMR) feed blocks was investigated. An experimental feed block with a low cost stover was compared with a commercial feed block produced by Miracle Feeds and Fodder Pvt. Ltd. that consisted of a premium sorghum stover (about 50%) and concentrate in equal proportions. Concentrate component consisted of bran and husks/hulls (18%), oilcakes (18%), molasses (8%) with the rest contributed by maize grain, urea, minerals and vitamins. In the experimental DTMR feed block the premium stover was replaced by low cost stover and rest of the composition was same. The two blocks were fed ad libitum to growing sheep measuring intake, digestibility and weight gain. No difference was observed in digestibility between the groups fed the commercial and the experimental block. Intake in the group fed the commercial block was 37 g/kg LW compared to 32.8 g/kg LW in the experimental block group (P=0.07). Daily live weight gain in the former group was twice that of the latter (90 vs. 45g; P=0.04). However, both feeding regimes were uneconomical, with the experimental feeding regime even resulting in monetary loss

Flexible Approach to <i>Stemona</i> Alkaloids: Total Syntheses of (−)-Stemospironine and Three New Diastereoisomeric Analogs

Total syntheses of (−)-stemospironine and three new diastereoisomeric analogs have been completed through a flexible strategy devised for <i>Stemona</i> alkaloids. The azabicycle <b>7</b> is the pivotal intermediate, from which the sequence splits according to each particular target. The most remarkable differential feature for stemospironine is the installation of the spiranic γ-lactone through an intramolecular Horner–Wadsworth–Emmons olefination. The configuration of the stereogenic center at C-11 was controlled by fine-tuning of the synthetic sequence

Synthesis of Novel Nucleoside Analogues Built on a Bicyclo[4.1.0]heptane Scaffold

A new class of carbocyclic nucleoside analogues built on a bicyclo[4.1.0]­heptane scaffold, a perspective novel pseudosugar pattern, have been conceived as anti-HSV agents on the basis of initial protein–ligand docking studies. The asymmetric synthesis of a series of these compounds incorporating different nucleobases has been efficiently completed starting from 1,4-cyclohexanedione

Synthesis of Nanoscale Coordination Polymers in Femtoliter Reactors on Surfaces

In the present work, AFM-assisted lithography was used to perform the synthesis of a coordination polymer inside femtoliter droplets deposited on surfaces. For this, solutions of the metal salt and the organic ligand were independently transferred to adjacent tips of the same AFM probe array and were sequentially delivered on the same position of the surface, creating femtoliter-sized reaction vessels where the coordination reaction and particle growth occurred. Alternatively, the two reagents were mixed in the cantilever array by loading an excess of the inks, and transferred to the surface immediately after, before the precipitation of the coordination polymer took place. The <i>in situ</i> synthesis allowed the reproducible obtaining of round-shaped coordination polymer nanostructures with control over their <i>XY</i> positioning on the surface, as characterized by microscopy and spectroscopy techniques

An Optimized Glutamate Receptor Photoswitch with Sensitized Azobenzene Isomerization

A new azobenzene-based photoswitch, <b>2</b>, has been designed to enable optical control of ionotropic glutamate receptors in neurons via sensitized two-photon excitation with NIR light. In order to develop an efficient and versatile synthetic route for this molecule, a modular strategy is described which relies on the use of a new linear fully protected glutamate derivative stable in basic media. The resulting compound undergoes one-photon <i>trans</i>–<i>cis</i> photoisomerization via two different mechanisms: direct excitation of its azoaromatic unit and irradiation of the pyrene sensitizer, a well-known two-photon sensitive chromophore. Moreover, <b>2</b> presents large thermal stability of its <i>cis</i> isomer, in contrast to other two-photon responsive switches relying on the intrinsic nonlinear optical properties of push–pull substituted azobenzenes. As a result, the molecular system developed herein is a very promising candidate for evoking large photoinduced biological responses during the multiphoton operation of neuronal glutamate receptors with NIR light, which require accumulation of the protein-bound <i>cis</i> state of the switch upon repeated illumination

Mussel-Inspired Hydrophobic Coatings for Water-Repellent Textiles and Oil Removal

A series of catechol derivatives with a different number of linear alkyl chain substituents, and different length, have been shown to polymerize in the presence of aqueous ammonia and air, yielding hydrophobic coatings that present the ability to provide robust and efficient water repellency on weaved textiles, including hydrophilic cotton. The polymerization strategy presented exemplifies an alternative route to established melanin- and polydopamine-like functional coatings, affording designs in which <i>all</i> catechol (adhesive) moieties support specific functional side chains for maximization of the desired (hydrophobic) functionality. The coatings obtained proved effective in the transformation of polyester and cotton weaves, as well as filter paper, into reusable water-repellent, oil-absorbent materials capable of retaining roughly double their weight in model compounds (<i>n</i>-tetradecane and olive oil), as well as of separating water/oil mixtures by simple filtration