Macrocyclic protease inhibitors with reduced peptide character.

There is a real need for simple structures that define a ß-strand conformation, a secondary structure that is central to peptide-protein interactions. For example, protease substrates and inhibitors almost universally adopt this geometry on active site binding. A planar pyrrole is used to replace two amino acids of a peptide backbone to generate a simple macrocycle that retains the required geometry for active site binding. The resulting ß-strand templates have reduced peptide character and provide potent protease inhibitors with the attachment of an appropriate amino aldehyde to the C-terminus. Picomolar inhibitors of cathepsin L and S are reported and the mode of binding of one example to the model protease chymotrypsin is defined by X-ray crystallography.

Synthesis and evaluation of 2-(1H-indol-3-yl)-4-phenylquinolines as inhibitors of cholesterol esterase.

A series of 2-(substituted) phenyl and 2-indolyl quinoline derivatives (10a-l) was synthesized by an efficient microwave-assisted, trifluoroacetic acid-catalyzed, solvent-free method. Evaluation of the inhibitory activity led to the identification of two quinoline inhibitors of cholesterol esterase. 2-(1H-Indol-3-yl)-6-nitro-4-phenylquinoline (10l; IC50=1.98µM) was characterized as a mixed-type inhibitor with a pronounced competitive binding mode.

New cholesterol esterase inhibitors based on rhodanine and thiazolidinedione scaffolds.

We present a new class of inhibitors of pancreatic cholesterol esterase (CEase) based on 'priviledged' 5-benzylidenerhodanine and 5-benzylidene-2,4-thiazolidinedione structural scaffolds. The lead structures (5-benzylidenerhodanine 4a and 5-benzylidene-2,4-thiazolidinedione 4b) were identified in an in-house screening and these inhibited CEase with some selectivity over another serine hydrolase, acetylcholinesterase (AChE) (4a, CEase IC(50)=1.76 µM vs AChE IC(50)=5.14 µM and 4b, CEase IC(50)=5.89 µM vs AChE IC(50) >100 µM). A small library of analogs (5a-10a) containing a core amino acid in place of the glycerol group of the lead structures, was prepared to explore other potential binding interaction with CEase. These analogs inhibited CEase with IC(50) values ranging from 1.44 to 85 µM, with the majority exhibiting some selectivity for CEase versus AChE. The most potent compound of the library (10a) had 17-fold selectivity over AChE. We also report molecular docking (with CEase) and detailed kinetic analysis on the amino acid analogs to further understand the associated structure-activity relationships.

New peptolides from the cyanobacterium Nostoc insulare as selective and potent inhibitors of human leukocyte elastase.

Eight new cyanopeptolins (insulapeptolides A-H) were obtained from the cyanobacterium Nostoc insulare. Their isolation was guided by their bioactivity toward the target enzyme human leukocyte elastase, molecular biological investigations, and MALDI-TOF analysis. These peptides are selective inhibitors of human leukocyte elastase with activities in the nanomolar range. Insulapeptolide D was the most potent compound with an IC(50) value of 85 nM (K(i) value of 36 nM).