Application of Hydrazino Dinitrophenyl-Amino Acids as Chiral Derivatizing Reagents for Liquid Chromatographic Enantioresolution of Carbonyl Compounds

A new series of chiral derivatizing reagents (CDRs) consisting of five hydrazino dinitrophenyl (HDNP)-amino acids (CDR 1?C5) was prepared by a two-step synthesis procedure starting from 1,5-difluoro-2,4-dinitrobenzene (DFDNB). In the first step, five fluoro-dinitrophenyl (FDNP)-reagents, namely FDNP-l-Leu, FDNP-l-Val, FDNP-l-Phe, FDNP-l-Ala and FDNP-d-Phg were synthesized by substituting one of the fluorine atoms in DFDNB moiety with amino acids l-Leu, l-Val, l-Phe, l-Ala and d-Phg, respectively. In the following step, the remaining fluorine atom of the FDNP reagents was substituted with hydrazine hydrate to obtain five HDNP reagents (i.e. CDR 1?C5; HDNP-l-Leu, HDNP-l-Val, HDNP-l-Phe, HDNP-l-Ala and HDNP-d-Phg). These five CDRs were used for synthesis of diastereomers of six racemic carbonyl compounds which were resolved by high-performance liquid chromatography using C18 column and gradient eluting mixture of acetonitrile or methanol with triethylammonium phosphate buffer with UV detection at 348 nm. Microwave irradiation was used for synthesis of both the CDRs and the diastereomers. The newly synthesized CDRs were observed to be superior in comparison to their counterparts having amino acid amides as chiral auxiliaries in terms of cost effectiveness and providing better resolution of diastereomers. The method was validated for limit of detection, linearity, accuracy and precision.     

Stereoselective Synthesis of β-Amino Ketones: A Three-Component Mannich-Type Reaction of Aromatic Aldehydes,Anilines, and Cyclohexanone Using Amberlyst-15

A three-component Mannich-type reaction of aromatic aldehydes, anilines, and cyclohexanone in the presence of Amberlyst-15 affords the corresponding β-amino ketones in good yields at room temperature. The conversion is highly diastereoselective, favoring the formation of anti-isomers.     

Convenient Synthesis of α,α1 - bis (Substituted Furfurylidene) Cycloalkanones and Chalcones Under Microwave Irradiation.

Condensation of furfural with cycloalkanones and substituted acetophenones catalyzed by solid NaOH results in α, α¹-bis (substituted furfurylidene) cycloalkanones and chalcones in high yield under microwave irradiation for a duration of 2 minutes.     

Efficient Route to Highly Functionalized Chalcone-Based Pyranocoumarins via Iodine-Promoted Michael Addition Followed by Cyclization of 4-Hydroxycoumarins

Molecular iodine is used as an efficient promoter in the regioselective synthesis of highly functionalized chalcone-based pyranocoumarin derivatives using 4-hydroxycoumarin in acetic acid solvent at 100 °C. Under optimized reaction conditions, our protocol (Michael addition followed by intermolecular cyclization) has tolerance for many functional groups and gave products in good to excellent yields (75–98%) within 1–2 h.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]     

Effect of gamma radiation on wheat plant growth due to impact on gas exchange characteristics and mineral nutrient uptake and utilization

The experiment was conducted to determine the effect of gamma radiation on plant growth and development, flag leaf gas exchange characteristics such as net photosynthetic rate (P _N), stomatal conductance (g _s), and transpiration rate (E) and activity of key carbon and nitrogen assimilating enzymes like Rubisco, starch synthase (SS) and nitrate reductase (NR) in field grown wheat. Grains of cultivar PBW-343 were exposed to a ⁶⁰Co (Cobalt-60) gamma source at a dose range from 0 to 500 Gy (Gray). Gas exchange characteristics of flag leaf were measured using Infrared Gas Analyzer (IRGA), while mineral nutrients were analyzed spectrophotometrically. Our results show that an irradiation treatment, in general, caused an improvement in plant growth and yield characteristics such as shoot and root mass, root length and surface area, leaf area and chlorophyll SPAD index, tiller number and grain yield. However, irradiation exceeding 5 Gy reduced the magnitude of radiation advantage for most of the investigated physiological and biochemical traits. No germination was recorded at 500 Gy irradiation dose. A dose-dependant increase in shoot Fe in radiated plants up to 25 Gy reflected its higher plant root to shoot translocation which may yield micronutrient rich grains. At higher dose of 100 Gy, there was a drastic reduction in flag leaf membrane stability index (MSI), photosynthesis, Rubisco, NR, and nutrients like K, P, Mg, Fe, and Zn. Starch synthase enzyme activity was unaffected by gamma irradiation indicating that the negative effect of high dose (100 Gy) on the grain yield were caused by the adverse effect of radiation on the gas exchange attributes particularly photosynthesis, carbon, and nitrogen assimilation efficiency and the plant uptake of mineral nutrients. The study concludes that gamma radiation at a low dose (25 Gy or lower) stimulates, while a high dose (100 Gy and above) inhibits plant growth and development of wheat. The adverse effect at 100 Gy and beyond could be attributed to the poor carbon and nitrogen assimilation efficiency and the plant uptake of mineral nutrients, all of which are the ultimate determinant of plant health.     

X-Ray Crystallographic Investigation of Fully Acetylated N-(2-Deoxy-2-Acetamido-β-D-Glucopyranosyl)Alkanamides as N-Glycoprotein Linkage Region Analogs

To understand the structural significance of the linkage region of N-glycoproteins, three title sugar amides have been prepared as analogs and their molecular assembly and crystal structures have been solved to explore the effect of acetyl protection and aglycon variation on the conformation, particularly of the N-glycosidic linkage. Comparative analysis of these structures with those of free sugar amides reported earlier showed that conformation of the amido aglycon moiety is not altered significantly by the masking of hydroxyl groups in the form of acetate. The bifurcated antiparallel pattern involving N?H…O and C?H…O hydrogen bonds, a hallmark of the N-glycoprotein models GlcNAcβNHAc and GlcNAcβAsn, is absent in all of the fully protected title alkanamides. The asymmetric unit of the tri-O-acetylated GlcNAcβNHAc contains two different conformations, in one of which the double-pillared hydrogen bond network involving C1 and C2 acetamido groups is antiparallel, while it is parallel in the other. The co-occurrence of a molecular assembly motif—a double-pillared parallel and antiparallel hydrogen bonding pattern—is hitherto unknown in the crystal structures of N-glycoprotein linkage region models and analogs.     

Styrene/Methyl Methacrylate-Vinyltns-(methoxyethoxy)silane Copolymers: Synthesis,Characterization, and Thermal Degradation

Vinyltris(methoxyethoxy)silane (VTMES)was copolymerized with methyl methacrylate (MMA) and styrene (St) in bulk at 60°C using benzoyl peroxide as free radical initiator. The copolymer compositions were determined from elemental analysis, and reactivity ratios were calculated by the Kelen-Tüds graphical method. For MMA-VTMES, r₁ = 11.2 ± 0.88 and r₂ = 0 ± 0.16, and for St-VTMES, r₁ = 11.2 ± 2.0 and r₂ = 0 ± 0.34. In both systems r₂ is near zero, indicating that VTMES undergoes little or no polymerization under the experimental conditions. The influence of the silicon comonomer on some of the basic properties of the copolymers (e.g., intrinsic viscosity, solubility, and thermal behavior) was studied.     

Controlled Release of Covalently Bound Organic Molecules by Slow Hydrolysis for Potential Biocide Applications†

A study of the slow hydrolysis of labile acetal groups by low concentrations of lactic acid to release the active molecules is reported. A prototype molecule containing cyclic acetal groups, dimethyl‐2,3‐O‐benzylidene‐L‐tartrate (DMTAc) and the same molecule incorporated as a pendant group in a polyamide were studied for their hydrolysis by low concentrations of lactic acid. The release of benzaldehyde during slow hydrolysis is monitored by UV‐vis and ¹H‐NMR spectroscopy. This study is very useful to ultimately design and synthesize a polymer with covalently bound insecticidal/anti‐microbial/anti‐fungal materials for the development of controlled release formulations.     

A new eco-friendly strategy for the synthesis of novel antimicrobial spiro-oxindole derivatives via supramolecular catalysis

Novel spiro-oxindole derivatives were synthesised by one-pot multicomponent reaction using isatins, urea and 1,3-dicarbonyls. β-Cyclodextrin, an oligosaccharide, catalysed the reaction and can be reused for further reaction after recovery. This developed synthetic route is environmentally benign in which water is used as solvent to produce excellent yields of products. The synthesised compounds were evaluated for their antimicrobial activities against two bacteria and two fungi. All the synthesised spiro-oxindoles exhibit significant antimicrobial activity.