Effects of melatonin on sperm quality, enzyme activity, antioxidant gene expression and fertility of cryopreserved bovine semen.

Melatonin (MLT) has strong antioxidant capacity and can reduce the damage caused by oxidative stress in sperm, but there is still little content in the field we have studied. In this study, we are committed to scientific research on adding melatonin to Belgian blue bull semen diluent for cryopreservation. Different concentrations (0, 0.1, 0.3, 0.5 or 0.7 mg/mL) of MLT were added diluent. Sperm kinetic parameters, enzyme activity, antioxidant gene expression and fertility were analyzed after thawing. The results showed that MLT concentration of 0.3 mg/mL exerted positive effects on post-thaw kinetic parameters. Compared with other groups, 0.3 mg/mL MLT treated sperm acrosome and plasma membrane integrity, catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) levels significantly increased. Meanwhile, the mRNA expression of antioxidant genes SOD2, CAT and GPx increased in the 0.3 mg/mL MLT treatment group, and the mRNA expression of apoptosis genes Caspase-3 and Bax were significantly reduced. In addition, in vitro fertilization (IVF) embryo cleavage, blastocyst rate and artificial insemination (AI) pregnancy rate were higher in 0.3 mg/mL MLT. Therefore, MLT showed cryoprotective capacity to the freezing diluent used for Belgian blue bull sperm during the process of freezing-thawing, and the optimal concentration of MLT for the frozen diluent was 0.3 mg/mL.

Trisubstituted alkenes with a single activator as dipolarophiles in a highly diastereo- and enantioselective [3+2] cycloaddition with vinyl epoxides under Pd-catalysis.

1,1,2-Trisubstituted alkenes with a single strongly electronic withdrawing activator, which are unreactive electron-deficient alkenes in transition metal-catalyzed [3+2] cycloaddition with vinyl three-membered heterocycles, were used in the Pd-catalyzed asymmetric cycloaddition of vinyl epoxides, affording multifunctionalized tetrahydrofurans in high yields with high diastereo- and enantioselectivities.

Diastereo- and Enantioselective Palladium-Catalyzed Dearomative [3+2] Cycloaddition of 3-Nitroindoles.

Diastereo- and enantioselective cycloaddition of 3-nitroindoles with vinyl aziridine was realized under Pd-catalysis using commercially available Walphos as the ligand, affording pyrroloindolines in high yields with high diastereo- and enantioselectivities. The reaction can be scaled up to a gram scale and the reaction products are easily converted to amino pyrroloindoline and other pyrroloindoline derivatives.

Highly Diastereo- and Enantioselective Palladium-Catalyzed [3 + 2] Cycloaddition of Vinyl Epoxides and α,ß-Unsaturated Ketones.

An asymmetric [3 + 2] cycloaddition reaction of vinyl epoxides with α,ß-unsaturated ketones, the single activated electron-deficient alkenes, has been achieved under Pd-catalysis in excellent diastereo- and enantioselectivity. The utilities of the protocol are demonstrated by transformation of the products into other useful chiral molecules. Density functional theory calculations rationalize the stereocontrol of the reaction.

Highly diastereo- and enantioselective palladium-catalyzed [3+2] cycloaddition of vinyl aziridines and α,ß-unsaturated ketones.

A palladium-catalyzed asymmetric [3+2] cycloaddition reaction of vinylaziridines with α,ß-unsaturated ketones, wherein the alkenes have a single activator, is realized in high diastereo- and enantioselectivity, thus affording 3,4-disubstituted pyrrolidines in high yields with excellent ee values. The introduction of a methyl group at C1 of the vinyl group the vinylaziridines greatly improves the stereochemistry of the reaction. A plausible transition state is proposed.