Adaptability and grain yield stability of rice hybrids and varieties in Venezuela

The development of new high-performance and stable cultivars requires test multi-environmental validation to deal with the effect of genotype by environment interaction (GEI). With the objective to determine adaptability and stability for grain yield in hybrids and rice varieties through the models AMMI, SREG and REML/BLUP. Six experiments were evaluated during the 2015-2016 dry season in the main producing regions of Venezuela. The ANOVA detected differences for genotype (G), environment (E) and their interaction (GEI), representing 19, 65 and 16 % of the total variation, respectively, with prevalence of hybrid by localities interaction. The first major components of the AMMI and GGE biplot models explained 77 and 83 % of GEI, respectively. The three models coincided and identified the hybrid RHA-180 (H6) with improved average performance, adapted and stable. The hybrid HIAAL (H3) was the most prominent. Among the checks, 'Pionero FL' (V3) was the most stable with moderate yield; the opposite occurred with ‘Soberana FL’ (V4) and ‘SD-20A’ (V1), that the AMMI and GGE biplot models identified with high and unstable performances and specific adaptation to locality INIA Guárico (L1), not coinciding with the mixed model. Two mega-environments were identified with the winning genotypes H6 and V4. There was divergence between AMMI and GGE biplot to identify discriminatory and representative locations. The Plot 199 (L3) was the most representative, while the location L1 discriminated better the genotypes. The GGE biplot analysis was more informative and complete for the GEI analysis.

2-Diphenylphosphinomethyl-3-methylpyrazine

The lateral metalation-electrophilic trapping reaction of alkyl-substituted pyrazines has always been challenging and poorly regioselective, with the corresponding derivatives often being isolated in moderate yield. In this contribution, we first report on the preparation of an unsymmetrically-substituted pyrazine, that is 2-diphenylphosphinomethyl-3-methylpyrazine, by subjecting to metalation with n-BuLi the commercially available 2,3-dimethylpyrazine, followed by interception of the putative lithiated benzyl-type intermediate with Ph2PCl. Such a functionalization has been successfully carried out in the absence of additional ligands, working either in THF at −78 °C or in a more environmentally friendly solvent like cyclopentyl methyl ether at 0 °C, with the desired phosphine derivative being isolated in 70–85% yield. The newly synthesized adduct has been fully characterized by means of multinuclear magnetic resonance spectroscopic techniques, and also by preparing a selenium derivative, which furnished single crystals that were suitable for X-ray analysis.

A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

In-situ-generated N-aryl nitrile imines derived from trifluoroacetonitrile efficiently react with polycyclic 1,4-quinones, yielding fused pyrazole derivatives as the exclusive products. The reactions proceed via the initially formed [3 + 2]-cycloadducts, which undergo spontaneous aerial oxidation to give aromatized heterocyclic products. Only for 2,3,5,6-tetramethyl-1,4-benzoquinone, the expected [3 + 2]-cycloadduct exhibited fair stability and could be isolated in moderate yield (53%). The presented method offers a straightforward access to hitherto little known trifluoromethylated polycyclic pyrazoles. All products were isolated as pale colored solids with medium-intensity absorption maxima in the range of 310–340 nm for naphthoquinone-derived products and low-intensity bands in the visible region (≈400 nm) for the anthraquinone series.

Silver Catalyzed Decarbonylative [3 + 2] Cycloaddition of Cyclobutenediones and Formamides

As an important moiety in natural products, N,O-acetal has attracted wide attention in the past few years. An efficient method to construct N,O-acetal has been developed. Using silver catalyst, cyclobutenediones were smoothly converted to the corresponding γ-aminobutenolides in the presence of formamides, in which cyclobutenediones likely proceed with a key decarbonylative [3 + 2] cycloaddition process. In this way, a series of products with varied substituents were isolated in moderate yield and fully characterized.

Synthesis of alkyl derivatives of 3,7,10-trioxo-2,4,6,8,9,11-hexaaza[3.3.3]propellane and evaluation of their biological activity

Today 3,7,10-trioxo-2,4,6,8,9,11-hexaaaza[3.3.3]propellane (THAP) has not yet received widespread re-search attention due to the complexity of the synthesis. This work is devoted to the development of a method for the THAP derivatives synthesis, as well as to the study of their biological activity in comparison with al-kyl-substituted glycolurils (subject of comparison). ТНАРwas N-alkylated to furnish novel hexaalkyl deriva-tives of ТНАРwith methyl, ethyl and propyl substituents. The conditionsfor obtaining the maximum yield of the target productwere optimizedon the base of methyl derivative. The reaction proceeded in DMSO/КОНat 75–80ºC for 13hours in a moderate yield of 56%. The ethyl and propyl derivatives of ТНАРwere synthe-sized under the same conditions. The biological activity of the obtained ТНАРalkyl derivatives and glycoluril alkyl derivatives was evaluated against Sporosarcina ureae, Bacillus pumilus, Salmonella typhimurium and Staphylococcus aureus bacteria and influenza A virus. All the samples were found to exhib-it antibacterial activity against Staphylococcus aureus.It was shown that 2,4,6,8,9,11-hexapropyl-ТНАР, di-tert-butyl-diphenyl-, di-tert-butyl-dibenzyl-, di-tert-butyl-dimethyl-and di-isopropyl-dibenzylglycoluril, have exhibited also toxicity to living cells besides antiviral activity

Direct deuteration of hinokitiol and its mechanistic study

ABSTRACT Hinokitiol has a broad antibacterial activity against bacteria and fungi. While its biosynthetic pathway has been intensively studied, its dynamics in natural environments, such as biodegradation pathway, remain unclear. In this study, the authors report a direct deuterium labeling of hinokitiol as a traceable molecular probe to serve those studies. Hinokitiol was subjected to the H2-Pd/C-D2O conditions and deuterated hinokitiol was obtained with excellent deuteration efficiencies and in moderate yield. The 1H and 2H NMR spectra indicated that all ring- and aliphatic hydrogens except that on C-6 were substituted by deuterium. According to the substrate scope and computational chemistry, deuteration on tropolone ring was suggested to proceed via D+-mediated process, and which was supported by the results of the experiment with trifluoroacetic acid and Pd(TPP)4. On the other hand, the deuteration on aliphatic group was predicted to be catalyzed by Pd(II) species.

Radical Mediated Aerobic Oxidation of Substituted Styrenes and Stilbenes

A 2,2-azobis(isobutyronitrile) (AIBN) catalyzed oxidative cleavage of alkenes with molecular oxygen as the oxidant has been described. Carbonyl compounds and oxiranes were obtained as products in moderate yield under mild...

Enzyme-assisted Cyclization of Chalcones to Flavanones

Enzyme catalyzed synthesis is an eco-friendly technique in organic synthesis, having several benefits over conventional methods. In the present work, we describe a simple process of laccase and chloroperoxidase assisted cyclization of chalcones, leading to the formation of flavanones. The reaction proceeds in a mixture of phosphate buffer and ethanol, under oxygen atmosphere at room temperature, yielding the corresponding flavanone in good to moderate yield. The relative configuration of the products at C2 is tentatively assigned as S*-flavanone based on the coupling constants with the methylenic protons H3α,β. In comparison to the chemical methods, we describe a process which can be achieved efficiently under mild conditions using oxygen as oxidant.

Ethyl (S)-2-Benzamido-5-[(4,6-dimethylpyrimidin-2-yl)amino]pentanoate

Pyrimidines are compounds with a wide range of biological activities, and the synthesis of pyrimidine derivatives—useful in chemical and medicinal applications—is important in medicinal chemistry. This work shows the synthesis under microwave irradiation of the novel compound ethyl (S)-2-benzamido-5-[(4,6-dimethylpyrimidin-2-yl)amino]pentanoate (3) from (S)-N-α-benzoyl-l-arginine ethyl ester hydrochloride (1) and acetylacetone (2). Compound 3 was easily purified, obtained in moderate yield (70%), and fully characterized by UV-Vis, FTIR-ATR spectroscopy, 1H-NMR, 13C-NMR, HRMS, and EI-MS.

Umpolung Reactions of α-Tosyloximino Esters in a Flow System

An umpolung reaction of α-tosyloximino esters in a flow system is disclosed. Tandem N,N-dialkylations with two different Grignard reagents gave the desired N,N-dialkylated products in moderate to good yields. In addition, a tandem N,N,C-trialkylation of an α-tosyloximino ester with three different Grignard reagents has been successfully achieved to afford the desired N,N,C-trialkylated product in moderate yield.