Asymmetric Intramolecular Desymmetrization of <i>meso</i>-α,α′-Diazido Alcohols with Aryldiazoacetates: Assembly of Chiral C₃ Fragments with Three Continuous Stereocenters

The chiral Cu-complex-catalyzed intramolecular interception of <i>meso</i>-α,α′-diazido alcohols with aryldiazoacetates is explored. Most of the enantioenriched α-imino esters with three continuous stereocenters are produced with good to excellent yield and enantioselectivity, and a chiral pocket model is proposed for rationalization of the asymmetric desymmetrization

Ingestive behaviour of beef cattle grazing brachiaria brizantha cv. marandu pastures submitted to continuous stocking regimes.

O conhecimento dos aspectos relacionados à interface planta:animal em sistemas de produção em pastagens ganha enorme relevância quando se tem como objetivo principal trabalhar dentro de princípios baseados no equilíbrio e racionalidade do uso dos recursos inerentes ao processo produtivo. Dessa forma, caracterizar os componentes da estrutura do dossel forrageiro e o efeito que os mesmos exercem sobre o comportamento ingestivo de animais em pastejo assume grande importância, uma vez que podem influenciar de forma relevante o consumo de forragem. Dentro desse contexto, o presente trabalho teve como objetivo procurar elucidar aspectos pertinentes à interface planta:animal através da quantificação do tamanho e da taxa de bocado, tempo gasto nas atividades de pastejo, ruminação e ócio pelos animais, e o consumo diário de forragem em pastos de Brachiaria brizantha cv. Marandu pastejados por bovinos em regime de lotação contínua e taxa de lotação variável. O experimento foi realizado em área do Departamento de Zootecnia da USP/ESALQ, em Piracicaba, SP, entre 01 de novembro de 2001 e 14 de fevereiro de 2003. Os tratamentos corresponderam a quatro alturas de dossel forrageiro (10, 20, 30 e 40 cm) mantidas em steady state, e foram alocados às unidades experimentais segundo um delineamento de blocos completos c casualizados, com quatro repetições. Os resultados revelaram uma redução em consumo de forragem com a diminuição da altura do dossel forrageiro (1,3; 1,8, 1,8 e 2,0 kg MS.kg PV -1 para 10, 20, 30 e 40 cm, respectivamente), conseqüência da redução em tamanho de bocado (0,5; 0,8; 1,2 e 1,5 g MS.bocado -1 para 10, 20, 30 e 40 cm, respectivamente). Os animais, na tentativa de tentar compensar a redução em consumo, aumentaram a taxa de bocado (46,3; 30,3; 23,8 e 17,5 bocados.minuto -1 para 10, 20, 30 e 40 cm, respectivamente) e, na condição de 10 cm de dossel forrageiro, aumentaram, também, o tempo de pastejo (11,4; 10,7; 10,6 e 10,5 horas.dia -1 para 10, 20, 30 e 40 cm, respectivamente). Concluiu-se que a ingestão de forragem pode ser controlada através de variações em condição e estrutura do dossel forrageiro, situação essa que demonstra o potencial de planejamento e monitoramento de estratégias de pastejo baseadas em metas de condição de dossel para níveis variáveis de exigências nutricionais, épocas do ano e espécie animal.Knowledge of aspects related to plant:animal interface in pastoral systems acquire greater importance when the main objective is to rationalize and optimize the use of any resource available. In that scenario, characterization of structural sward components and their effect on ingestive behaviour of grazing animals is a key element, since they can have a relevant influence on herbage intake. Against this background, the objective of this experiment was to study aspects of the plant:animal interface quantifying bite size, bite rate, time spent on grazing, rumination and rest as well as herbage intake of cattle grazing Brachiaria brizantha cv Marandu pastures submitted to continuous stocking managements. The experiment was carried out at Departamento de Zootecnia, USP/ESALQ, Piracicaba, SP, from 01 November 2001 until 14 February 2003. Treatments corresponded to four steady state conditions characterized by sward surface heights (SSH) of 10, 20, 30 and 40 cm, assigned to experimental units according to a complete randomized block design, with four replications. The results revealed a reduction in herbage intake with decreasing SSH (1.3, 1.8, 1.8 and 2.0 kg DM.kg LW -1 for 10, 20, 30 and 40 cm, respectively), consequence of a reduction in bite size (0.5, 0.8, 1,2 and 1.5 g DM.bite -1 for 10, 20, 30 and 40 cm, respectively). Animals, in an attempt to compensate the decrease in herbage intake, increased their bite rate (46.3, 30.3, 23.8 and 17.5 bites.minute -1 for 10, 20, 30 and 40 cm, respectively) and, for the 10 cm SSH, increased, also, their grazing time (11.4, 10.7, 10.6 and 10.5 hours.day -1 for 10, 20, 30 and 40 cm, respectively). It was concluded that herbage intake can be controlled by variations in sward structure and condition, which points to the potential for planning and monitoring grazing strategies based on sward targets for variable levels of animal requirements, time of the year and animal species

Total Synthesis of (±)-Cephanolides B and C via a Palladium-Catalyzed Cascade Cyclization and Late-Stage sp³ C–H Bond Oxidation

Herein, we report the first total syntheses of complex cephalotaxus diterpenoids cephanolide B and C from commercially available 5-bromo-2-methylanisole. Key to the success of this synthetic route is a palladium-catalyzed cascade cyclization reaction, which allowed us to efficiently forge the 6–5–6 <i>cis</i>-fused tricyclic ring systems found in the entire family of cephalotaxus diterpenoids. Additionally, site-selective late-stage sp³ C–H bond oxidation served as a key strategic element in the chemical synthesis of cephanolide C

Total Synthesis of (±)-Cephanolides B and C via a Palladium-Catalyzed Cascade Cyclization and Late-Stage sp³ C–H Bond Oxidation

Herein, we report the first total syntheses of complex cephalotaxus diterpenoids cephanolide B and C from commercially available 5-bromo-2-methylanisole. Key to the success of this synthetic route is a palladium-catalyzed cascade cyclization reaction, which allowed us to efficiently forge the 6–5–6 <i>cis</i>-fused tricyclic ring systems found in the entire family of cephalotaxus diterpenoids. Additionally, site-selective late-stage sp³ C–H bond oxidation served as a key strategic element in the chemical synthesis of cephanolide C

Preparation of Optically Active <i>cis</i>-Cyclopropane Carboxylates: Cyclopropanation of α‑Silyl Stryenes with Aryldiazoacetates and Desilylation of the Resulting Silyl Cyclopropanes

Optically active <i>cis</i>-cyclopropane carboxylates are prepared via the Rh₂(<i>S</i>-PTAD)₄-catalyzed cyclopropanation of α-silyl styrenes with aryl diazoacetates followed by desilylation of the resulting silyl cyclopropane carboxylates. The conjugation of the aryl ring with CC bond and π stacking are proposed for the stereoselectivity of cyclopropanation, and configuration inversion is observed with the desilylation process

Preparation of Optically Active <i>cis</i>-Cyclopropane Carboxylates: Cyclopropanation of α‑Silyl Stryenes with Aryldiazoacetates and Desilylation of the Resulting Silyl Cyclopropanes

Optically active <i>cis</i>-cyclopropane carboxylates are prepared via the Rh₂(<i>S</i>-PTAD)₄-catalyzed cyclopropanation of α-silyl styrenes with aryl diazoacetates followed by desilylation of the resulting silyl cyclopropane carboxylates. The conjugation of the aryl ring with CC bond and π stacking are proposed for the stereoselectivity of cyclopropanation, and configuration inversion is observed with the desilylation process

A Total Synthesis of Paeoveitol

A four-step total synthesis of paeoveitol (<b>1</b>), a recently disclosed norditerpene natural product from <i>Paeonia vetchii</i>, is reported. This highly concise synthetic route was guided by biosynthetic considerations and enabled by an unusual intermolecular <i>ortho</i>-quinone methide [4 + 2]-cycloaddition reaction, which proceeded with excellent regio- and diastereoselectivity. Density functional theory (DFT) calculations point to a crucial intermolecular hydrogen bond and π–π stacking interaction that govern selectivity in this process

<i>N</i>-Heterocyclic Carbene-Catalyzed Internal Redox Reaction of Alkynals: An Efficient Synthesis of Allenoates

An efficient <i>N</i>-heterocyclic carbene (NHC)-catalyzed internal redox reaction of alkynals that bear a γ leaving group has been developed. This process provides a new access to a range of allenoates in good yields. Preliminary results demonstrate that the enantioselective variant can also be achieved

Bioinspired Collective Total Synthesis of (±)-Rhynchines A–E

Herein, we present the first racemic total synthesis of the structurally complex monoterpene indole alkaloids rhynchines A–E, starting from commercially available methyl nicotinate and 3-(2-bromoethyl)-1H-indole. The success of our synthesis is attributed to the utilization of a bioinspired synthetic strategy, which facilitated the rapid construction of the pentacyclic core skeleton of the target molecules through biomimetic skeletal rearrangement and late-stage C–H oxidative cyclization. Additionally, silica-gel-promoted tautomerization played a crucial role as a strategic element in the chemical synthesis of rhynchines A and B

Additional file 1: Table S1. of Neuroprotective effect of a novel Chinese herbal decoction on cultured neurons and cerebral ischemic rats

Assessments of physiological parameters before, during and after ischemia (MCAO) in control and PSR pre-treated rats. Figure S1. Representative TTC-stained brain slices for sham and MCAO rats, with the latter animals divided into 4 groups that were pre-treated with vehicle, 1.1 g/kg, 2.2 g/kg or 5.5 g/kg PSR. Figure S2. Representative TTC-stained brain slices for sham and MCAO rats, with the latter animals divided into 4 groups that were post-treated with vehicle, 1.1 g/kg, 2.2 g/kg or 5.5 g/kg PSR. (DOCX 3065 kb