Polymer-supported Schiff base complexes in oxidation reactions

Covering: July 1998 to the end of July 1999. Previous review: J. Chem. Soc., Perkin Trans. 1, 1999, 641.

The synthesis of thiols, selenols, sulfides, selenides, sulfoxides, selenoxides, sulfones and selenones

Hsp90 is a chaperone protein with important roles in maintaining transformation and in elevating the survival and growth potential of cancer cells. Currently there is an increasing interest in developing inhibitors of this protein as anticancer therapeutics. One of such inhibitors, the purine-scaffold class, has been reported to be potent and selective against Hsp90 both in vitro and in vivo models of cancer. Here, a series of 8-arylsulfanyl, -sulfoxyl, and -sulfonyl adenine members of the purine class was synthesized and evaluated as inhibitors of the chaperone. The structure-activity relationship and selectivity for tumor Hsp90 of compounds within the series is presented. Our results suggest that 8-arylsulfanyl adenine derivatives are good inhibitors of chaperone activity, whereas oxidation of the sulfides to sulfoxides or sulfones leads to compounds of decreased activity. The study identifies derivative 11v as the most potent Hsp90 inhibitor of the purine-scaffold series published to date (EC(50) = 30 nM), and also as the compound of this class with highest selectivity for tumor vs normal cell Hsp90 (700 to 3000-fold). Most rewardingly, this work has allowed for the identification of Hsp90 inhibitors with selective affinities for Hsp90-client protein complexes, derivatives that may represent useful pharmacological tools in dissecting Hsp90-regulated processes.

Evaluation of 8-arylsulfanyl, 8-arylsulfoxyl, and 8-arylsulfonyl adenine derivatives as inhibitors of the heat shock protein 90.

Electronic structure of active sites plays a crucial role in redox catalysts. Herein, graphitic carbon nitride (g-C3N4) decorated with metallic MoO2 heterojunction nanocomposites were successfully synthesized through a facile calcination route. XPS, UPS, UV–vis and PL spectra results suggest electron transfer from the conduction band (CB) of g-C3N4 to unfilled π* band of metallic MoO2 in the metal-semiconductor heterojunction. The electron transfer ensures high intrinsic oxidative desulfurization activity for MoO2/g-C3N4 composites. Radical scavenger experiments indicate that the electron transfer facilitates the enrichment of electron density around Mo active sites and control the rate-determining step of oxidative desulfurization. The approach can be extended to other low valent transition metal oxides possessing d electrons for enhanced catalytic activity in redox reactions.

Electronic structure of heterojunction MoO2/g-C3N4 catalyst for oxidative desulfurization

Green oxidations. The use of potassium permanganate supported on manganese dioxide

Silica gel and alumina have been found to mediate the oxidation of sulfides and sulfoxides with (CH3)3COOH and OXONE. With all combinations except (CH3)3COOH/alumina, sulfides were oxidized with reasonably good selectivity to sulfoxides. These studies afforded insights into the mechanisms of surface-mediated processes. Adsorption studies, combined with the effect of partial silylation of silica gel, indicate that oxidation of sulfides by (CH3)3COOH/silica gel occurs at least predominantly via nucleophilic attack by the sulfide on (CH3)3COOH, which is activated by being bound to isolated silanol sites on the silica gel surface (Scheme 2), whereas oxidation of sulfoxides involves nucleophilic attack by (CH3)3COOH on the sulfoxide, which is activated by being bound to associated silanol sites (Scheme 3). Oxidation of sulfoxides by (CH3)3COOH/alumina involves attack of (CH3)3COO- on the sulfoxide bound to free Al+ sites on the surface (Scheme 4B). Mediation of oxidation by OXONE involves instead activation by...

and Jesse C. Tung

Papers

Surface-Mediated Reactions. 8. Oxidation of Sulfides and Sulfoxides with tert-Butyl Hydroperoxide and OXONE1