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The disclosure provides proteasome inhibitors that can be used to halt cell division of rapidly dividing cells by preventing the degradation of cell cycle-regulating proteins, such as cyclins, cyclin-dependent kinase inhibitors, and p53. The proteasome in

The peptidic β-lactone proteasome inhibitors (PIs) cystargolides A and B were used to conduct structure-activity relationship (SAR) studies in order to assess their anticancer potential. A total of 24 different analogs were designed, synthesized and evaluated for proteasome inhibition, for cytotoxicity towards several cancer cell lines, and for their ability to enter intact cells. X-ray crystallographic analysis and subunit selectivity was used to determine the specific subunit binding associated with the structural modification of the β-lactone (P1), peptidic core, (Px and Py), and end-cap (Pz) of our scaffold. The cystargolide derivative 5k, structurally unique at both Py and P1, exhibited the most promising inhibitory activity for the β5 subunit of human proteasomes (IC50 = 3.1 nM) and significant cytotoxicity towards MCF-7 (IC50 = 416 nM), MDA-MB-231 (IC50 = 74 nM) and RPMI 8226 (IC50 = 41 nM) cancer cell lines. Cellular infiltration assays revealed that minor structural modifications have significant effects on the ability of our PIs to inhibit intracellular proteasomes, and we identified 5k as a promising candidate for continued therapeutic studies. Our novel drug lead 5k is a more potent proteasome inhibitor than carfilzomib with mid-to-low nanomolar IC50 measurements and it is cytotoxic against multiple cancer cell lines at levels approaching those of carfilzomib.

Amide bonds are one of the underpinning linkages in all living systems and are fundamental within drug discovery. Current methods towards their synthesis frequently rely on the use of dipolar aprotic solvents; however, due to increasingly stringent regula

Tetrakis(dimethylamido)diboron and tetrahydroxydiboron are herein reported as new catalysts for the synthesis of aryl amides by catalytic condensation of aromatic carboxylic acids with amines. The developed protocol is both simple and highly efficient over a broad range of substrates. This method thus represents an attractive approach for the use of diboron catalysts in the synthesis of amides without having to resort to stoichiometric or additional dehydrating agents.

6-Nitro- and 6,8-dinitronaphth-1,2-oxathiole S,S-dioxides (7b and 7c) have been prepared from the parent naphthosultone 7a and compared with 5-nitrobenz-3H-1,2-oxathiole S,S-dioxide (1b) as coupling reagents for peptide synthesis.Nucleophilic attack of a carboxylate salt on these strained five-membered sultones leads to activated esters 3 and 9 which rapidly react with amines (except in the case of 9c).The rate constant for the formation of ester 9b is higher than that of 3b.Amides or peptides are formed in slightly better yields with the naphthosultone 7b than with the benzosultone 1b.The naphthosultones are also preferred over the benzosultones from the point of view of amount of 5(4H)-oxazolone formation from N-benzoyl amino acids and the degree of racemization.However the rate of alkaline hydrolysis of 7b is slower than that of 1b.All these results may be rationalized by a better intramolecular acyl transfer reaction in the more rigid mixed anhydride intermediate 8b.There is no dependence on in the rate equation for aminolysis of esters 3b and 9b by benzylamine in THF, acetonitrile, or DMF and the aminolysis is probably anchimerically assisted by a neighbouring S=O group.Esters 3b are more selective acylating agents for primary amino groups in the presence of secondary ones than esters 9b and this observation is exploited in a synthesis of maytenine by selective acylation of spermidine.