ABSTRACT
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.
Subject(s)
Amidohydrolases/metabolism , Hydroxamic Acids/chemistry , Salicylates/chemistry , Trypanosoma brucei brucei/enzymology , Trypanosomiasis, African/parasitology , Amidohydrolases/antagonists & inhibitors , Humans , Protein Binding , Small Molecule Libraries , Structure-Activity Relationship , Substrate Specificity , Trypanosomiasis, African/enzymology , Zinc/chemistry , Zinc/metabolismABSTRACT
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.
Subject(s)
Amidohydrolases/antagonists & inhibitors , Enzyme Inhibitors/pharmacology , Glucosamine/analogs & derivatives , Phosphatidylinositols/pharmacology , Trypanosoma brucei brucei/enzymology , Amidohydrolases/metabolism , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/chemistry , Glucosamine/chemical synthesis , Glucosamine/chemistry , Glucosamine/pharmacology , Molecular Conformation , Phosphatidylinositols/chemical synthesis , Phosphatidylinositols/chemistry , Structure-Activity Relationship , Substrate Specificity/drug effectsABSTRACT
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.
ABSTRACT
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.
