Toward the Synthesis of Sceptrin and Benzosceptrin: Solvent Effect in Stereo- and Regioselective [2+2] Photodimerization and Easy Access to the Fully Substituted Benzobutane: Toward the Synthesis of Sceptrin and Benzosceptrin: Solvent Effect in Stereo- and Regioselective [2+2] Photodimerization and Easy Access to the Fully

Umpolung of N-Tosylhydrazones: Synthesis of N-Cyano Tosylhydrazones and Their [3,3]-Sigmatropic Rearrangement to 2-Aminoimidazoles

The umpolung of N-tosylhydrazones was reported for the first time. Synthesis of N-cyano tosylhydrazones was developed, and various N-cyano tosylhydrazones were prepared in good yields. An umpolung N-tosylhydrazones mechanism was proposed. Meanwhile, the [3,3]-sigmatropic rearrangement of N-cyano tosylhydrazones was examined, and the corresponding 2-aminoimidazoles were given.

Synthesis of new imine-/amine-bearing imidazo[1,2-a]pyrimidine derivatives and screening of their cytotoxic activity

Imidazo[1,2-a]pyrimidine derivatives bearing imine groups (3a-e) were successfully synthesized in moderate to good yields using microwave-assisted heating. Corresponding amine derivatives (4a-e) were also obtained by the reduction reaction of the imine derivatives (3a-e). All synthesized products were characterized by FT-IR, 1H NMR, 13C NMR, and LC-MS spectroscopic techniques. In silico ADMET, Lipinski, and drug-likeness studies of the compounds were conducted and all were found to be suitable drug candidates. The cytotoxicity of the potential drug molecules was screened against the breast cancer cell lines MCF-7 and MDA-MB-231 and the healthy model HUVEC by the sulforhodamine B method. According to the antiproliferative studies, compounds 3d and 4d showed remarkable inhibition of MCF-7 cells with IC50 values of 43.4 and 39.0 μM and of MDA-MB-231 cells with IC50 values of 35.9 and 35.1 μM, respectively. In particular, compound 3d selectively inhibited the proliferation of MCF-7 1.6-fold and MDA-MB-231 2.0-fold relative to healthy cells. Moreover, the apoptotic mechanism studies indicated that compound 4d induced apoptosis by moderately increasing the ratio of Bax/Bcl-2 genes. Imidazo[1,2-a]pyrimidine derivative 3d, a promising cytotoxic agent, may be helpful in the discovery of new and more efficient anticancer agents for breast cancer treatment.

Strategic Use of Visible-Light Photoredox Catalysis in Natural Product Synthesis

Recent progress in the development of photocatalytic reactions promoted by visible light is leading to a renaissance in the use of photochemistry in the construction of structurally elaborate organic molecules. Because of the rich functionality found in natural products, studies in natural product total synthesis provide useful insights into functional group compatibility of these new photocatalytic methods as well as their impact on synthetic strategy. In this review, we examine total syntheses published through the end of 2020 that employ a visible-light photoredox catalytic step. To assist someone interested in employing the photocatalytic steps discussed, the review is organized largely by the nature of the bond formed in the photocatalytic step.

Total Synthesis of (±)-Sceptrin

A four-step synthesis of the dimeric pyrrole-imidazole alkaloid sceptrin is reported. The brevity of the route is based on a simple solution developed for selective assembly of the cyclobutane core of the natural product. The photochemical intermolecular [2 + 2] dimerization of a useful hymenidin surrogate enables direct entry to this enigmatic class of biologically active marine secondary metabolites.

Organo-Halogens and their Possible Involvement in Prebiotic Chemistry

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In this review, we examined the possibility that some halogenated organic derivatives were used in the primitive ocean at the beginning of life on Earth. Firstly, we described the existence of extraterrestrial halogenated molecules, then we studied their nonbiological syntheses on the present Earth, especially in volcanic environments. In order to demonstrate the diversity of today’s halogenated biomolecules, representative examples are given and the biosynthesis of some of them is summarized. Finally, we proposed two aspects of the chemistry of halogenated compounds that may have been useful en route to biomolecules, firstly the use of methyl chloride as the first methylation reagent, secondly the synthesis and use of α-chloro-carbonyl derivatives.

[2+2] Photodimerization of Stilbazoles Promoted by Oxalic Acid in Suspension

In this study, a very simple technique to perform efficiently photodimerization of some vinylpyridines is reported. By irradiating a stirred mixture of several stilbazoles with solid oxalic acid dihydrate dispersed in a nonpolar (i.e., cyclohexane) or moderately polar (benzene, dichloromethane, dioxane) solvent, the corresponding dimeric cyclobutane adducts were obtained in high yields and excellent regio- and stereoselectivities. The strategy could also be applied successfully to oily, waxy, or even insoluble stilbazoles. Moreover, the oxalic acid loading could be lowered to substoichiometric amounts. When further optimizations were needed, our strategy was found to be highly flexible to identify other oligocarboxylic acids as alternative additives to improve, or even overturn, the regioselectivity. Oxalic acid and other oligocarboxylic acids were found to be capable of orienting more than 50 stilbazoles toward photodimerization under these conditions.