Xing Zheng

Ph₃P/I^–-promoted dichlorination and dibromination of epoxides by using XCH₂CH₂X (X = Cl or Br) as the halogen source and reaction solvent is described. All reagents are widely available and easy to handle, and mild conditions and operational simplicity make this protocol attractive.

Flavan-3-ols are a series of natural products widely present in plants and show versatile biological activities. The structures of such compounds are characterized by owing two adjacent chiral centers and three rings. Their interesting structures and promising biological activities have driven increasing research developments toward the preparation of enantioenriched flavan-3-ols. This review summarizes the recent approaches for the asymmetric synthesis of chiral flavan-3-ols from two strategies in the construction of chiral centers. The key steps in the synthetic protocol involve Sharpless asymmetric dihydroxylation, Shi asymmetric epoxidation and Sharpless asymmetric epoxidation.

Firstly discovered in 1980s, human immunodeficiency virus (HIV) continues to affect more and more people. However, there is no effective drug available for the therapy of HIV infection. Betulinic acid existing in various medicinal herbs and fruits exhibits multiple biological effects, especially its outstanding anti-HIV activity, which has drawn the attentions of many pharmacists. Among the derivatives of betulinic acid, some compounds exhibited inhibitory activities at the nanomolar concentration, and have entered phase II clinical trials. This paper summarizes the current investigations on the anti-HIV activity of betulinic acid analogues, and provides valuable data for subsequent researches.

Bromotrifluoromethane (CF₃Br) is a simple, inexpensive and abundant industrial material employed as a trifluoromethylating reagent. However, only limited strategies using CF₃Br as a fluorine source are reported. Herein, we describe a visible-light-induced hydrotrifluoromethylation of alkenes and alkynes with CF₃Br. The reaction proceeds under mild conditions with good functional group tolerance, providing a new route for the application of BrCF₃ in organic synthesis.

The highly diastereoselective synthesis of CF₃-containing vicinal diamines by a convenient two-step procedure without the need to isolate the intermediate products is described.

Difluoromethylation of N-arylsulfonyl hydrazones with difluorocarbene generated from difluoromethylene phosphobetaine (Ph₃P⁺CF₂CO₂⁻) is described to give various difluoromethyl aryl sulfones.

A novel series of iodo-chrysin derivatives with resorcinol as raw materials were synthesized according to Baker-Venkataraman reaction and their inhibitory activities in vitro against thyroid cancer cell lines (SW-579 and TT) were evaluated by the standard methyl thiazole tetrazolium (MTT) method. Biological test results showed that these derivatives possessed stronger anti-thyroid cancer activities than 5-FU. Compound 21 showed the strongest activity against SW-579 cell lines with IC50 value of 3.4μM and compound 10 showed the strongest activity against TT cell lines with IC50 value of 6.2μM, it was better than 5-FU (59.3μΜ, 18.4μM respectively).

A near-infrared (NIR) “off–on” fluorescent probe was developed for the detection of H₂S. The new probe possesses a highly selective and sensitive response to H₂S. The probe has low toxicity and was successfully used to detect H₂S in biological serum samples and living cells.