Development of α-keto-based inhibitors of cruzain, a cysteine protease implicated in Chagas disease
摘要:
Trypanosoma cruzi, a protozoan parasite, is the causative agent of Chagas disease, a major cause of cardiovascular disease in many Latin American countries. There is an urgent need to develop an improved therapy due to the toxicity of existing drugs and emerging drug resistance. Cruzain, the primary cysteine protease of T cruzi, is essential for the survival of the parasite in host cells and therefore is an important target for the development of inhibitors as potential therapeutics. A novel series of alpha-ketoamide-, alpha-ketoacid-, alpha-ketoester-, and aldehyde-based inhibitors of cruzain has been developed. The inhibitors were identified by screening protease targeted small molecule libraries and systematically optimizing the P1, P2, P3, and P1 ' residues using specific structure-guided methods. A total of 20 compounds displayed picomolar potency in in vitro assays and three inhibitors representing different alpha-keto-based inhibitor scaffolds demonstrated anti-trypanosomal activity in cell culture. A 2.3 angstrom crystallographic structure of cruzain bound with one of the alpha-ketoester analogs is also reported. The structure and kinetic assay data illustrate the covalent binding, reversible inhibition mechanism of the inhibitor. Information on the compounds reported here will be useful in the development of new lead compounds as potential therapeutic agents for the treatment of Chagas disease and as biological probes to study the role that cruzain plays in the pathology. This study also demonstrates the validity of structure-guided approaches to focused library design and lead compound optimization. (c) 2005 Elsevier Ltd. All rights reserved.
First synthesis of enantiomerically pure N-protected β-amino-α-keto esters from α-amino acids and dipeptides
摘要:
A racemization-free route from N-protected alpha-amino acids and dipeptides to N-protected beta-amino-alpha-keto esters is described, involving the sequence: diazoketone formation. Wolff rearrangement in methanol, diazo transfer, and oxidation with dimethyldioxirane.
The chemoselectiveoxidation of α-hydroxy acids to α-keto acids catalyzed by 2-azaadamantane N-oxyl (AZADO), a nitroxylradicalcatalyst, is described. Although α-keto acids are labile and can easily release CO2 under oxidation conditions, the use of molecular oxygen as a cooxidant enables the desired chemoselectiveoxidation.
Cyanomethylene triphenylphosphoranes of N-protected amino acids were synthesized from the corresponding N-urethane protected α-amino acid N-carboxyanhydrides (UNCAs) by reaction with cyanomethyltriphenylphosphonium chloride in good yields. These compounds are precursors of α-keto esters which are candidates for mimicking the tetrahedric transition state in enzyme inhibitors.