Sulfated polysaccharide from Sargassum tenerrimum attenuates oxidative stress induced reactive oxygen species production in in vitro and in zebrafish model.

The sulfated polysaccharide (SP) was isolated from the brown alga S. tenerrimum. The chemical composition of SP composed of 57 ± 0.

Nucleophilic ring-opening reactions of trans-2-aroyl-3-aryl-cyclopropane-1,1-dicarboxylates with hydrazines.

trans-2-Aroyl-3-aryl-cyclopropane-1,1-dicarboxylates when treated with arylhydrazines in refluxing EtOH gave dihydropyrazoles, whereas with hydrazines in refluxing AcOH, they formed cyclopropane-fused pyridazinones. Although in both cases the corresponding hydrazones are formed initially, the former case involves a subsequent 5-exo-tet nucleophilic ring-opening, and the later, a 6-exo-trig nucleophilic attack by the other hydrazone nitrogen. The products are obtained in moderate to excellent yields with complete regio-and diastereoselectivity.

Domino Synthesis of Tetrasubstituted Thiophenes from 1,3-Enynes with Mercaptoacetaldehyde.

Domino synthesis of tetrasubstituted thiophenes is described from 1,3-enynes and mercaptoacetaldehyde using DABCO at room temperature via a Michael addition, 5-exo-dig carboannulation, and oxidation sequence under air. The broad substrate scope and mild reaction conditions are significant practical features.

[3+3] Annulation of donor-acceptor cyclopropanes with mercaptoacetaldehyde: application to the synthesis of tetrasubstituted thiophenes.

A conceptually new method for synthesis of tetrasubstituted thiophenes in two steps from trans-2-aroyl-3-aryl-cyclopropane-1,1-dicarboxylates and 1,4-dithiane-2,5-diol has been developed. It involves AlCl3-mediated [3+3] annulation of the cyclopropane-derived 1,3-zwitterionic intermediates with in situ generated mercaptoacetaldehyde, followed by DBU-induced rearrangement of the resulting tetrahydrothiopyranols. The target thiophenes are produced in 55-82% yields.

Highly diastereoselective synthesis of 1-pyrrolines via SnCl4-promoted [3 + 2] cycloaddition between activated donor-acceptor cyclopropanes and nitriles.

Activated donor-acceptor cyclopropanes underwent formal [3 + 2] cycloaddition with nitriles in the presence of SnCl(4). The product 1-pyrrolines were isolated as single cis-diastereomers in moderate to good yields.