Diastereo- and Enantioselective Propargylation of 5H-Thiazol-4-ones and 5H-Oxazol-4-ones as Enabled by Cu/Zn and Cu/Ti Catalysis.

Reported is the asymmetric propargylic substitution (APS) reaction of 5H-thiazol-4-ones using a Cu/Zn dual metal catalytic system and the APS reaction of 5H-oxazol-4-ones using a Cu/Ti catalytic system. These reactions furnish functional-group-rich, terminal-alkyne-containing products with two vicinal stereocenters in high yields and with good to excellent diastereo- and enantioselectivities. This study demonstrates the use of dual metal catalytic systems as a viable approach to improve the selectivity profiles of the copper-catalyzed APS reactions.

Enantioselective Propargylation of Polyols and Desymmetrization of meso 1,2-Diols by Copper/Borinic Acid Dual Catalysis.

A copper/borinic acid dual catalytic reaction enabled the enantioselective propargylation of aliphatic polyols. Readily available reagents and catalysts were used in this transformation, which displayed good to excellent chemo- and stereoselectivity for a broad array of substrates. The method was also applicable to the desymmetrization of meso 1,2-diols to furnish products with three stereogenic centers and a terminal alkyne group in one operation.

Site-switchable mono-O-allylation of polyols.

Site-selective modification of complex molecules allows for rapid accesses to their analogues and derivatives, and, therefore, offers highly valuable opportunities to probe their functions. However, to selectively manipulate one out of many repeatedly occurring functional groups within a substrate represents a grand challenge in chemistry. Yet more demanding is to develop methods in which alterations to the reaction conditions lead to switching of the specific site of reaction. We report herein the development of a Pd/Lewis acid co-catalytic system that achieves not only site-selective, but site-switchable mono-O-allylation of polyols with readily available reagents and catalysts. Through exchanging the Lewis acid additives that recognize specific hydroxyls in a polyol substrate, our system managed to install a versatile allyl group to the target in a site-switchable manner. Our design demonstrates remarkable scope, and is amenable to the direct derivatization of various complex, bioactive natural products.

[Effects of visfatin gene overexpression on insulin sensitivity in the insulin-resistant rats induced by high-fat diet].

OBJECTIVE: To investigate the effects of visfatin gene overexpression on insulin sensitivity in insulin-resistant (IR) rats induced by high-fat diet. METHODS: The recombinant visfatin plasmid was constructed and transfected into IR rats induced by high-fat diet. The euglycemic-hyperinsulinemic clamp experiments were performed for evaluation the change of insulin sensitivity before and after administration. RESULTS: The expression plasmid of visfatin were successfully constructed. After 3 days for plasmid injecting, plasma visfatin levels and glucose infusion rates were significantly increased (2.19 +/- 0.36 vs 0.98 +/- 0.27 and 32.6 +/- 1.2 vs 24.0 +/- 1.2 mg x kg(-1) x min(-1), respectively, all P < 0.01), and total cholesterol and high-density lipoprotein cholesterol (HDL-C) were significantly decreased (2.36 +/- 0.22 vs 1.60 +/- 0.21 mmol/L and 1.41 +/- 0.24 vs 0.88 +/- 0.11 mmol/L, respectively, all P < 0.05) in high-fat diet rats. CONCLUSION: The transfection of visfatin plasmid enhanced plasma visfatin level and improved insulin sensitivity in IR rats induced by high-fat diet.