ABSTRACT
The halodecarboxylation of heteroarene carboxylic acids by treatment with N-bromosuccinimide or N-chlorosuccinimide was performed. This procedure provides a convenient route to synthetically useful mono-halogenated heteroarene intermediates such as halo-indoles, -aza-indoles, -indazoles and -aza-indazoles. The mild conditions employed and simple protocol provides an advantage over traditional halodecarboxylation procedures that require expensive and toxic metal catalysts, basic conditions, time-consuming intermediate isolation and elevated reaction temperatures.
ABSTRACT
New tools are required to ensure the adequate control of the neglected tropical disease human African trypanosomiasis. Annual reports of infection have recently fallen to fewer than 5000 cases per year; however, current therapies are hard to administer and have safety concerns and, hence, are far from ideal. Trypanosome alternative oxidase is an exciting target for controlling the infection; it is unique to the parasite, and inhibition of this enzyme with the natural product ascofuranone has shown to clear in vivo infections. We report the synthesis and associated structure activity relationships of inhibitors based upon this natural product with correlation to T. b. brucei growth inhibition in an attempt to generate molecules that possess improved physicochemical properties and potential for use as new treatments for human African trypanosomiasis.
Subject(s)
Mitochondrial Proteins/antagonists & inhibitors , Oxidoreductases/antagonists & inhibitors , Plant Proteins/antagonists & inhibitors , Protozoan Proteins/antagonists & inhibitors , Sesquiterpenes/isolation & purification , Trypanocidal Agents/isolation & purification , Trypanosoma brucei brucei/drug effects , Trypanosoma/drug effects , Trypanosoma/enzymology , Inhibitory Concentration 50 , Molecular Structure , Parasitic Sensitivity Tests , Sesquiterpenes/chemical synthesis , Sesquiterpenes/chemistry , Structure-Activity Relationship , Trypanocidal Agents/chemical synthesis , Trypanocidal Agents/chemistry , Trypanosoma brucei brucei/growth & developmentABSTRACT
African trypanosomiasis is a parasitic disease affecting 5000 humans and millions of livestock animals in sub-Saharan Africa every year. Current treatments are limited, difficult to administer and often toxic causing long term injury or death in many patients. Trypanosome alternative oxidase is a parasite specific enzyme whose inhibition by the natural product ascofuranone (AF) has been shown to be curative in murine models. Until now synthetic methods to AF analogues have been limited, this has restricted both understanding of the key structural features required for binding and also how this chemotype could be developed to an effective therapeutic agent. The development of 3 amenable novel synthetic routes to ascofuranone-like compounds is described. The SAR generated around the AF chemotype is reported with correlation to the inhibition of T. b. brucei growth and corresponding selectivity in cytotoxic assessment in mammalian HepG2 cell lines. These methods allow access to greater synthetic diversification and have enabled the synthesis of compounds that have and will continue to facilitate further optimisation of the AF chemotype into a drug-like lead.
Subject(s)
Drug Discovery , Enzyme Inhibitors/pharmacology , Mitochondrial Proteins/antagonists & inhibitors , Oxidoreductases/antagonists & inhibitors , Plant Proteins/antagonists & inhibitors , Trypanocidal Agents/pharmacology , Trypanosoma brucei brucei/drug effects , Trypanosoma/drug effects , Trypanosomiasis, African/drug therapy , Ubiquinone/analogs & derivatives , Dose-Response Relationship, Drug , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/chemistry , Humans , Mitochondrial Proteins/metabolism , Molecular Structure , Oxidoreductases/metabolism , Plant Proteins/metabolism , Structure-Activity Relationship , Trypanocidal Agents/chemical synthesis , Trypanocidal Agents/chemistry , Trypanosoma/enzymology , Trypanosoma brucei brucei/growth & development , Trypanosomiasis, African/parasitology , Ubiquinone/chemical synthesis , Ubiquinone/chemistry , Ubiquinone/pharmacologyABSTRACT
The development of renewable alternatives to diesel and jet fuels is highly desirable for the heavy transportation sector, and would offer benefits over the production and use of short-chain alcohols for personal transportation. Here, we report the development of a metabolically engineered strain of Escherichia coli that overproduces medium-chain length fatty acids via three basic modifications: elimination of beta-oxidation, overexpression of the four subunits of acetyl-CoA carboxylase, and expression of a plant acyl-acyl carrier protein (ACP) thioesterase from Umbellularia californica (BTE). The expression level of BTE was optimized by comparing fatty acid production from strains harboring BTE on plasmids with four different copy numbers. Expression of BTE from low copy number plasmids resulted in the highest fatty acid production. Up to a seven-fold increase in total fatty acid production was observed in engineered strains over a negative control strain (lacking beta-oxidation), with a composition dominated by C(12) and C(14) saturated and unsaturated fatty acids. Next, a strategy for producing undecane via a combination of biotechnology and heterogeneous catalysis is demonstrated. Fatty acids were extracted from a culture of an overproducing strain into an alkane phase and fed to a Pd/C plug flow reactor, where the extracted fatty acids were decarboxylated into saturated alkanes. The result is an enriched alkane stream that can be recycled for continuous extractions. Complete conversion of C(12) fatty acids extracted from culture to alkanes has been demonstrated yielding a concentration of 0.44 g L(-1) (culture volume) undecane.
