Acetyl Coenzyme A Analogues as Rationally Designed Inhibitors of Citrate Synthase

Abstract

In this study, we probed the inhibition of pig heart citrate synthase (E.C. 4.1.3.7) by synthesising seven analogues either designed to mimic the proposed enolate intermediate in this enzyme reaction or developed from historical inhibitors. The most potent inhibitor was fluorovinyl thioether 9 (Ki=4.3 μm), in which a fluorine replaces the oxygen atom of the enolate. A comparison of the potency of 9 with that of its non‐fluorinated vinyl thioether analogue 10 (Ki=68.3 μm) revealed a clear “fluorine effect” favouring 9 by an order of magnitude. The dethia analogues of 9 and 10 proved to be poor inhibitors. A methyl sulfoxide analogue was a moderate inhibitor (Ki=11.1 μm), thus suggesting hydrogen bonding interactions in the enolate site. Finally, E and Z propenoate thioether isomers were explored as conformationally constrained carboxylates, but these were not inhibitors. All compounds were prepared by the synthesis of the appropriate pantetheinyl diol and then assembly of the coenzyme A structure according to a three‐enzyme biotransformation protocol. A quantum mechanical study, modelling both inhibitors 9 and 10 into the active site indicated short CF⋅⋅⋅H contacts of ≈2.0 Å, consistent with fluorine making two stabilising hydrogen bonds, and mimicking an enolate rather than an enol intermediate. Computation also indicated that binding of 9 to citrate synthase increases the basicity of a key aspartic acid carboxylate, which becomes protonated.

Cooperative Gold/Zinc‐Catalyzed Cascade Approach to Tryptophan Derivatives from N‐arylhydroxylamines and Alkynes

“…The treatment of 6 f with 2‐phenylethane‐1‐thiol in the presence of Pd 2 (dba) 3 and Xantphos afforded sulfane 9 in 71% yield (Scheme 2d) [14] . The protecting group of adduct 6 d was readily removed in the presence of hydrazine hydrate (Scheme 2e) [15] …”

“…[14] The protecting group of adduct 6 d was readily removed in the presence of hydrate (Scheme 2e). [15]…”

Recent progress in alkynylation with hypervalent iodine reagents

“…Building upon their work on the fluorination of thioalkynes, 84 O'Hagan, Bu ¨hl and coworkers synthesized fluorovinyl This journal is © The Royal Society of Chemistry 2023 thioether acetyl coenzyme A analogue 16 (Scheme 17). 85 The fluorovinyl thioether moiety was obtained by alkynylation of a thiol using TMS-EBX (4b) followed by treatment of the obtained thioalkyne with AgF/I 2 /triethylamine. The compound was shown to be a potent inhibitor of citrate synthase (K i = 4.3 mM).…”

Intersecting Xenobiology and Neometabolism To Bring Novel Chemistries to Life

“…Indeed, a recent report highlights the value of rationally designing fluorometabolites that bind to citrate synthase with different degrees of affinity. [96] The number of applications of fluoroacetyl-CoA as starting point for neometabolism will increase once the toxicity of fluoroacetate is avoided (or, at least, attenuated). According to the KEGG database, [97] acetate participates directly in 139 biological reactions, and the figures reach a staggering 215 reactions when acetyl-CoA is considered.…”