RESUMO
The zinc-metalloenzyme GlcNAc-PI de-N-acetylase is essential for the biosynthesis of mature GPI anchors and has been genetically validated in the bloodstream form of Trypanosoma brucei, which causes African sleeping sickness. We screened a focused library of zinc-binding fragments and identified salicylic hydroxamic acid as a GlcNAc-PI de-N-acetylase inhibitor with high ligand efficiency. This is the first small molecule inhibitor reported for the trypanosome GPI pathway. Investigating the structure activity relationship revealed that hydroxamic acid and 2-OH are essential for potency, and that substitution is tolerated at the 4- and 5-positions.
Assuntos
Amidoidrolases/metabolismo , Ácidos Hidroxâmicos/química , Salicilatos/química , Trypanosoma brucei brucei/enzimologia , Tripanossomíase Africana/parasitologia , Amidoidrolases/antagonistas & inibidores , Humanos , Ligação Proteica , Bibliotecas de Moléculas Pequenas , Relação Estrutura-Atividade , Especificidade por Substrato , Tripanossomíase Africana/enzimologia , Zinco/química , Zinco/metabolismoRESUMO
A series of synthetic analogues of 1-D-(2-amino-2-deoxy-α-D-glucopyranosyl)-myo-inositol 1-(1,2-di-O-hexadecanoyl-sn-glycerol 3-phosphate), consisting of 7 variants of either the D-myo-inositol, D-GlcpN or the phospholipid components, were prepared and tested as substrates and inhibitors of GlcNAc-PI de-N-acetylase, a genetically validated drug target enzyme responsible for the second step in the glycosylphosphatidylinositol (GPI) biosynthetic pathway of Trypanosoma brucei. The D-myo-inositol in the physiological substrate was successfully replaced by cyclohexanediol and is still a substrate for T. brucei GlcNAc-PI de-N-acetylase. However, this compound became sensitive to the stereochemistry of the glycoside linkage (the ß-anomer was neither substrate or inhibitor) and the structure of the lipid moiety (the hexadecyl derivatives were inhibitors). Chemistry was successfully developed to replace the phosphate with a sulphonamide, but the compound was neither a substrate or an inhibitor, confirming the importance of the phosphate for molecular recognition. We also replaced the glucosamine by an acyclic analogue, but this also was inactive, both as a substrate and inhibitor. These findings add significantly to our understanding of substrate and inhibitor binding to the GlcNAc-PI de-N-acetylase enzyme and will have a bearing on the design of future inhibitors.
Assuntos
Amidoidrolases/antagonistas & inibidores , Inibidores Enzimáticos/farmacologia , Glucosamina/análogos & derivados , Fosfatidilinositóis/farmacologia , Trypanosoma brucei brucei/enzimologia , Amidoidrolases/metabolismo , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Glucosamina/síntese química , Glucosamina/química , Glucosamina/farmacologia , Conformação Molecular , Fosfatidilinositóis/síntese química , Fosfatidilinositóis/química , Relação Estrutura-Atividade , Especificidade por Substrato/efeitos dos fármacosRESUMO
Quinols have been developed as a class of potential anti-cancer compounds. They are thought to act as double Michael acceptors, forming two covalent bonds to their target protein(s). Quinols have also been shown to have activity against the parasite Trypanosoma brucei, the causative organism of human African trypanosomiasis, but they demonstrated little selectivity over mammalian MRC5 cells in a counter-screen. In this paper, we report screening of further examples of quinols against T. brucei. We were able to derive an SAR, but the compounds demonstrated little selectivity over MRC5 cells. In an approach to increase selectivity, we attached melamine and benzamidine motifs to the quinols, because these moieties are known to be selectively concentrated in the parasite by transporter proteins. In general these transporter motif-containing analogues showed increased selectivity; however they also showed reduced levels of potency against T. brucei.
Assuntos
Sistemas de Liberação de Medicamentos , Hidroquinonas/farmacologia , Tripanossomicidas/farmacologia , Trypanosoma brucei brucei/efeitos dos fármacos , Benzamidinas/síntese química , Benzamidinas/química , Benzamidinas/farmacologia , Linhagem Celular , Humanos , Hidroquinonas/síntese química , Hidroquinonas/química , Concentração Inibidora 50 , Modelos Moleculares , Estrutura Molecular , Triazinas/síntese química , Triazinas/química , Triazinas/farmacologia , Tripanossomicidas/síntese química , Tripanossomicidas/químicaRESUMO
We report the extension of the copper(II) tetrafluoroborate catalysed opening of epoxides with alcohols to include a wider variety of alcohols, a range of solvents and a method to purify the products from the reaction.
RESUMO
The intramolecular iodo-aldol cyclization of alpha-substituted enoate aldehydes and ketones is described. Using prochiral starting materials, the reaction produces hetero- and carbocycles containing quaternary centers adjacent to secondary or tertiary centers. The reactions occur in good yields and are highly selective for the trans-products, having the hydroxyl and iodomethyl groups on opposite faces of the ring system.