Microwave Radiation Applied to the Synthesis of -butyrolactone Derivatives

Many natural products with a broad spectrum of biological effects bear the g-butyrolactone ring. Given the difficulty in isolating large amounts of butyrolactones from natural sources, interest in synthesizing structural analogs of these compounds and in studying their biological properties has increased. In this review, we summarize the main synthetic methodologies to construct γ-butyrolactone derivatives by using multicomponent processes. DOI: http://dx.doi.org/10.17807/orbital.v13i4.165

Microwave Radiation Applied to the Synthesis of -butyrolactone Derivatives

Many natural products with a broad spectrum of biological effects bear the g-butyrolactone ring. Given the difficulty in isolating large amounts of butyrolactones from natural sources, interest in synthesizing structural analogs of these compounds and in studying their biological properties has increased. In this review, we summarize the main synthetic methodologies to construct γ-butyrolactone derivatives by using multicomponent processes. DOI: http://dx.doi.org/10.17807/orbital.v13i4.165

Hydrogenation of Biomass-derived 5-hydroxymethylfurfural (HMF) over Pd Catalysts in Aqueous Medium

We hydrogenated biomass-derived 5-hydroxymethylfurfural (HMF) in aqueous medium in a reaction catalyzed by palladium nanoparticles (Pd) on carbonaceous materials with different morphology and hydrophobic degree. The Pd catalysts were prepared by dipping the carbonaceous material into a Pd0 micro-emulsion. The catalyst support affected catalytic HMF hydrogenation. By using micrometric active carbon (AC) combined with cup-stacked carbon nanotubes (CSCNTs) and Pd, we obtained a micro/nanostructured material designated Pd/CSCNT-AC, which performed better than the other carbonaceous materials containing similar Pd loading. Pd/CSCNT-AC catalyzed HMF hydrogenation at the C=O double bond more selectively, giving between 85% and 99% selectivity toward 2,5-bis(hydroxymethyl)furan (BHMF). We also investigated how temperature, hydrogen pressure, and reaction time affected HMF hydrogenation

Synthesis and stereochemical assignment of methyl 3-(3-hydroxyphenoxy) acrylate via cis-trans photoisomerization

Methyl 3-(3-hydroxyphenoxy)acrylate (2), a new and important starting material for several reactions and a potential precursor of the natural product 3-(3-hydroxyphenoxy)-2-propenal (1), was synthesized from resorcinol and methyl propiolate. The trans configuration of the double bond present in 2 was confirmed through a photoisomerization reaction.3-(3-Hidroxi-fenoxi)acrilato de metila (2), um novo e importante material de partida para inúmeras reações e um precursor potencial do produto natural 3-(3-hidroxi-fenoxi)-2-propenal (1), foi sintetizado a partir de resorcinol e propiolato de metila. A configuração trans da dupla ligação presente no composto 2 foi confirmada através de uma reação de fotoisomerização.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Synthesis of Analogues of Thyroid Hormones: Nuclear Receptor Modulators

Thyroid hormones are essential for the development and differentiation of all cells of the human body. This work reports the synthesis of some synthetic structural analogues of thyroid hormones, which may be modulators of the thyroid hormone receptor. The known compounds GC-1 (Sobetirome) and CG-24 were successfully prepared and two novel analogous molecules were also synthesized by a new and efficient synthetic methodology. DOI: http://dx.doi.org/10.17807/orbital.v7i3.73

Structural basis of GC-1 selectivity for thyroid hormone receptor isoforms

Background: Thyroid receptors, TRα and TRβ, are involved in important physiological functions such as metabolism, cholesterol level and heart activities. Whereas metabolism increase and cholesterol level lowering could be achieved by TRβ isoform activation, TRα activation affects heart rates. Therefore, β-selective thyromimetics have been developed as promising drug-candidates for treatment of obesity and elevated cholesterol level. GC-1 [3,5-dimethyl-4-(4'-hydroxy-3'-isopropylbenzyl)-phenoxy acetic acid] has ability to lower LDL cholesterol with 600- to 1400-fold more potency and approximately two- to threefold more efficacy than atorvastatin (Lipitor©) in studies in rats, mice and monkeys. Results: To investigate GC-1 specificity, we solved crystal structures and performed molecular dynamics simulations of both isoforms complexed with GC-1. Crystal structures reveal that, in TRα Arg228 is observed in multiple conformations, an effect triggered by the differences in the interactions between GC-1 and Ser277 or the corresponding asparagine (Asn331) of TRβ. The corresponding Arg282 of TRβ is observed in only one single stable conformation, interacting effectively with the ligand. Molecular dynamics support this model: our simulations show that the multiple conformations can be observed for the Arg228 in TRα, in which the ligand interacts either strongly with the ligand or with the Ser277 residue. In contrast, a single stable Arg282 conformation is observed for TRβ, in which it strongly interacts with both GC-1 and the Asn331. Conclusion: Our analysis suggests that the key factors for GC-1 selectivity are the presence of an oxyacetic acid ester oxygen and the absence of the amino group relative to T3. These results shed light into the β-selectivity of GC-1 and may assist the development of new compounds with potential as drug candidates to the treatment of hypercholesterolemia and obesity

Microwave-Assisted Green Production of Furfural from D-xylose of Sugarcane Bagasse

D-xylose is a component of sugarcane bagasse that can be used as a renewable resource for the production of a variety of chemicals. By means of catalytic reactions in an aqueous medium, it was determined that D-xylose can efficiently be converted into furfural by the application of microwave as a green synthetic methodology. The highest yields of furfural were obtained at a HCl concentration of 4 mg/mL. When the reaction was performed at 200 °C, an optimum yield of 64% of furfural was observed after 10 min of reaction time, with 95% of the D-xylose being converted

Total synthesis of aripuanin, a megastigmane from Ficus aripuanensis

The first total synthesis of the natural product aripuanin, a megastigmane recently isolated, was achieved with moderate yields starting from isophorone