Current Organic Chemistry - Volume 23, Issue 25, 2019

Propargylamines are an important constituent of diverse, biologically active and industrially valuable compounds. These useful, convenient and effective compounds can be synthesized via the A³-coupling reactions between an aldehyde, amine, and alkyne in the presence of a catalyst. In the past years, most of the catalysts containing transition metals were applied in these reactions, but today, various heterogeneous catalysts, especially nanocatalysts are used. The purpose of this review was to introduce some modern catalysts for the A3-coupling reaction.

The disulfide bond possesses unique chemical and biophysical properties which distinguish it as one of the key structural elements of bioactive proteins and peptides, important drugs and other materials. The chemo-selective synthesis of these structures and the exploration of their function have been of longstanding interest to the chemistry community. The past decades have witnessed significant progress in both areas. This review will summarize the historically established and recently developed chemical methods in disulfide bond formation. The discussion will also be extended to the use of the disulfide linkers in small molecules, and peptide- and protein-drug conjugates. It is hoped that the combined overview of the fundamental chemistries and applications to drug discovery will inspire creative thinking and stimulate future novel uses of these versatile chemistries.

The reactions involving the formation of C-O bond using metal as a catalyst have emerged to be one of the most influential reactions for the synthesis of heterocycles in modern organic chemistry. Catalysis by metals offers diverse opportunities to invent new organic reactions with a promising range of selectivities such as chemoselectivity, regioselectivity, diastereoselectivity, and enantioselectivity. The methodologies used earlier for synthesis were less approachable to the organic chemist because of their high cost, highly specified instrumentation and inconvenient methods. For both stereoselective and regioselective formation of five-membered O-containing heterocycles, cyclic reactions that are metal and non-metal-catalyzed have known to be very efficient. The present review article covers the applications of metal and non-metal as a catalyst for the synthesis of five-membered O-containing heterocycles.

For decades now, compounds in the cycloartane-type series have been shown to have versatile pharmacological activities. However, no extensive review has been written to summarize these health-beneficial activities. Therefore, the purpose of this paper is to systematically highlight the biological activities of these compounds, including their antitumor and anti-osteoporosis effects, their effects on receptors, cytokine release, and chronic renal failure, as well as their tyrosinase inhibitory, anticomplement, anti-parasite, anti-HIV, and antituberculosis activities. In this review, we have summarized the structures of over 200 compounds based on their characteristics and described their structureactivity relationships (SARs), and potential mechanisms of action.

A series of palladium(II) complexes incorporating 1-substituted-3-methyl-3- phospholenes as the P-ligands were prepared from phospholene oxides by deoxygenation followed by complexation with PdCl2(PhCN)2. The two 1-substituted-3-methyl-3- phospholene ligands were trans position to each other in the Pd(II)-complexes. As the ligands contain a P-stereogenic center, the Pd-complexes were obtained as a 1:1 mixture of two stereoisomers, the homochiral (R,R and S,S) and the meso (R,S) forms, when racemic starting materials were used. An optically active Pd-complex containing (R)-1-propyl- 3-phospholene ligand was also prepared. Catalytic activity of an aryl- and an alkyl-3- phospholene-palladium(II)-complex was evaluated in hydroalkoxycarbonylation of styrene. The alkyl-derivative showed higher activity and selectivity towards the formation of the esters of 3-phenylpropionic acid. However, the overall activity of these PdCl2(phospholene)2-type complexes was low.