Highly potent bisphosphonate ligands for phosphoglycerate kinase

Three-Component Direct Phosphorylation of Aldehydes and Alkylation of Ketones: Synthesis of γ-Ketophosphine Oxides under Acidic Conditions

An effective and economical acid-promoted three-component reaction for the construction of C-P and C-C bonds for the synthesis of γ-ketophosphine oxides with water as the only byproduct was developed. Detailed mechanistic experiments confirmed that the reaction proceeds by phospha-aldol elimination, in which a benzylic carbocation is generated from the phosphorylation of aldehydes, which then reacts with ketone enolates under acidic conditions.

A guanidinium group is an effective mimic of the tertiary carbocation formed by isopentenyl diphosphate isomerase

Type I isopentenyl diphosphate isomerase is a metal-dependent enzyme that generates a tertiary carbocation intermediate during catalysis. This study describes an inhibitor (2-guanidinoethyl(dihydroxyphosphorylmethyl)phosphinate) of the isomerase that bears a guanidinium as a carbocation mimic and a phosphinylphosphonate as a non-hydrolyzable metal binding functionality. Inhibition kinetics show that the compound acts in a competitive manner with a K_i value of 129 nM (K_M,IPP/K_i = 27). An analogous inhibitor bearing a tertiary ammonium as the carbocation mimic was 50-fold less potent, suggesting that the planar guanidinium is a more effective carbocation mimic. Inhibitors bearing an acylated methanesulfonamide or a hydroxamate group in place of the pyrophosphate inhibited the enzyme at millimolar concentrations indicating that the isomerase is highly specific for binding to the diphosphate portion of the intermediate.

Synthesis of an α-phosphono-α,α-difluoroacetamide analogue of the diphosphoinositol pentakisphosphate 5-InsP7

Diphosphoinositol phosphates (PP-InsPs) are an evolutionarily ancient group of signalling molecules that are essential to cellular and organismal homeostasis. As the detailed mechanisms of PP-InsP signalling begin to emerge, synthetic analogues of PP-InsPs containing stabilised mimics of the labile diphosphate group can provide valuable investigational tools. We synthesised 5-PCF2Am-InsP5 (1), a novel fluorinated phosphonate analogue of 5-PP-InsP5, and obtained an X-ray crystal structure of 1 in complex with diphosphoinositol pentakisphosphate kinase 2 (PPIP5K2). 5-PCF2Am-InsP5 binds to the kinase domain of PPIP5K2 in a similar orientation to that of the natural substrate 5-PP-InsP5 and the PCF2Am structure can mimic many aspects of the diphosphate group in 5-PP-InsP5. We propose that 1, the structural and electronic properties of which are in some ways complementary to those of existing phosphonoacetate and methylenebisphosphonate analogues of 5-PP-InsP5, may be a useful addition to the expanding array of chemical tools for the investigation of signalling by PP-InsPs. The PCF2Am group may also deserve attention for wider application as a diphosphate mimic.

Further Understanding of the Reactivity Control of Bisphosphonates to a Metal Source for Fabricating Highly Ordered Mesoporous Films

Mesoporous metal organophosphonates having embedded organic functions are a promising platform to hybridize organics and non-siliceous inorganic frameworks in their molecular scale. However, the reactivity between a bisphosphonate and a metal source is dramatically different for their combination and then hampers to construct ordered mesoporous structures even when using amphiphilic organic molecules. By proposing an advanced method to adjust such reactivity, we recently succeeded in fabricating ordered mesoporous aluminum organophosphonate (AOP) films with chemically designable benzene units inside their hybrid frameworks. The reactivity of the organically bridged bisphosphonates has been controlled by utilizing dissimilar reactivities of acid-base pairs like P-OH and P-OEt groups to AlCl₃ . Here, we further prove our reactivity-control concept through the introduction of organic groups, such as those having symmetric thiophene, asymmetric amide, and hydrophilic ether units. Liquid-state ³¹ P NMR measurements further clarified the usefulness of the control of the -OH/ -OEt ratio in the same bisphosphonate molecules for obtaining highly ordered mesostructured AOP films.

Mono and double Mizoroki–Heck reaction of aryl halides with dialkyl vinylphosphonates using a reusable palladium catalyst under aqueous medium

2-Aryl or 2,2-diaryl vinylphosphonates can be selectively obtained by using aryl halides or dialkylvinylphosphonate as the limiting reagent.

MgF3- and AlF4- transition state analogue complexes of yeast phosphoglycerate kinase

The phospho-transfer mechanism of yeast phosphoglycerate kinase (PGK) has been probed through formation of trifluoromagnesate (MgF₃^-) and tetrafluoroaluminate (AlF₄^-) transition state analogue complexes and analyzed using ¹⁹F, ¹H waterLOGSY and ¹H chemical shift perturbation NMR spectroscopy. We observed the first ¹⁹F NMR spectroscopic evidence for the formation of metal fluoride transition state analogues of yeast PGK and also observed significant changes to proton chemical shifts of PGK in the presence, but not in the absence, of fluoride upon titration of ligands, providing indirect evidence of the formation of a closed ternary transition state. WaterLOGSY NMR spectroscopy experiments using an uncompetitive model were used in an attempt to measure ligand binding affinities within the transition state analogue complexes.

On the mechanism of phosphoenolpyruvate synthetase (PEPs) and its inhibition by sodium fluoride: potential magnesium and aluminum fluoride complexes of phosphoryl transfer

Phosphoenolpyruvate synthase (PEPs) catalyzes the conversion of pyruvate to phosphoenolpyruvate (PEP) using a two-step mechanism invoking a phosphorylated-His intermediate. Formation of PEP is an initial step in gluconeogenesis, and PEPs is essential for growth of Escherichia coli on 3-carbon sources such as pyruvate. The production of PEPs has also been linked to bacterial virulence and antibiotic resistance. As such, PEPs is of interest as a target for antibiotic development, and initial investigations of PEPs have indicated inhibition by sodium fluoride. Similar inhibition has been observed in a variety of phospho-transfer enzymes through the formation of metal fluoride complexes within the active site. Herein we quantify the inhibitory capacity of sodium fluoride through a coupled spectrophotometric assay. The observed inhibition provides indirect evidence for the formation of a MgF3−complex within the enzyme active site and insight into the phospho-transfer mechanism of PEPs. The effect of AlCl3on PEPs enzyme activity was also assessed and found to decrease substrate binding and turnover.

Facile synthesis of γ-ketophosphonates by an intermolecular Stetter reaction onto vinylphosphonates

The atom-economic and practical N-heterocyclic carbene (NHC) catalyzed Stetter reaction for the synthesis of γ-ketophosphonates by the reaction of aromatic aldehydes with vinylphosphonates is reported. The NHC derived from N-mesitylimidazolium salt (IMes) was an effective catalyst for this transformation, and the products were formed in moderate to good yields.

Pd-catalyzed highly regio-, diastereo-, and enantioselective allylic alkylation of α-fluorophosphonates

α-Fluorophosphonates with two chiral centers have been synthesised in high diastereo- and enatioselectivites via Pd-catalyzed AAA of 2-fluoro-2-(diethoxyphosphoryl)acetate with monosubstituted allylic substrates. Their transformations were also demonstrated.

Metal-free, hydroacylation of C=C and N=N bonds via aerobic C-H activation of aldehydes, and reaction of the products thereof

In this report, a thorough evaluation of the use of aerobically initiated, metal-free hydroacylation of various C=C and N=N acceptor molecules with a wide range of aldehydes is presented. The aerobic-activation conditions that have been developed are in sharp contrast to previous conditions for hydroacylation, which tend to use transition metals, peroxides that require thermal or photochemical degradation, or N-heterocyclic carbenes. The mildness of the conditions enables a number of reactions involving sensitive reaction partners and, perhaps most significantly, allows for α-functionalised chiral aldehydes to undergo radical-based hydroacylation with complete retention of optical purity. We also demonstrate how the resulting hydroacylation products can be transformed into other useful intermediates, such as γ-keto-sulfonamides, sultams, sultones, cyclic N-sulfonyl imines and amides.

Anticancer agents that counteract tumor glycolysis

Can we consider cancer to be a "metabolic disease"? Tumors are the result of a metabolic selection, forming tissues composed of heterogeneous cells that generally express an overactive metabolism as a common feature. In fact, cancer cells have increased needs for both energy and biosynthetic intermediates to support their growth and invasiveness. However, their high proliferation rate often generates regions that are insufficiently oxygenated. Therefore, their carbohydrate metabolism must rely mostly on a glycolytic process that is uncoupled from oxidative phosphorylation. This metabolic switch, also known as the Warburg effect, constitutes a fundamental adaptation of tumor cells to a relatively hostile environment, and supports the evolution of aggressive and metastatic phenotypes. As a result, tumor glycolysis may constitute an attractive target for cancer therapy. This approach has often raised concerns that antiglycolytic agents may cause serious side effects toward normal cells. The key to selective action against cancer cells can be found in their hyperbolic addiction to glycolysis, which may be exploited to generate new anticancer drugs with minimal toxicity. There is growing evidence to support many glycolytic enzymes and transporters as suitable candidate targets for cancer therapy. Herein we review some of the most relevant antiglycolytic agents that have been investigated thus far for the treatment of cancer.

Selective synthesis of α-fluoro-β-keto- and α-fluoro-β-aminophosphonates via electrophilic fluorination by selectfluor

A series of α-mono- and α,α-difluoro-β-ketophosphonates were synthesized in moderate to good yields with excellent selectivities via electrophilic fluorination by Selectfluor. Subsequently, synthetic potential of the obtained α-monofluoro-β-ketophosphonates was demonstrated by their application in synthesis of α-monofluoro-β-aminophosphonates, useful building blocks in the preparation of phosphapeptides.

Multisubstrate adduct inhibitors: drug design and biological tools

In drug discovery, different methods exist to create new inhibitors possessing satisfactory biological activity. The multisubstrate adduct inhibitor (MAI) approach is one of these methods, which consists of a covalent combination between analogs of the substrate and the cofactor or of the multiple substrates used by the target enzyme. Adopted as the first line of investigation for many enzymes, this method has brought insights into the enzymatic mechanism, structure, and inhibitory requirements. In this review, the MAI approach, applied to different classes of enzyme, is reported from the point of view of biological activity.

A convenient synthesis of the C-1-phosphonate analogue of UDP-GlcNAc and its evaluation as an inhibitor of O-linked GlcNAc transferase (OGT)

The C-1-phosphonate analogue of UDP-GlcNAc has been synthesized using an alpha-configured C-1-aldehyde as a key intermediate. Addition of the anion of diethyl phosphate to the aldehyde produced the hydroxyphosphonate. The configuration of this key intermediate was determined by X-ray crystallography. Deoxygenation, coupling of the resulting phosphonic acid with UMP and deprotection gave the target molecule as a di-sodium salt. This analogue had no detectable activity as an inhibitor of (OGT).

Regioselective synthesis of fluoroalkylated beta-aminophosphorus derivatives and aziridines from phosphorylated oximes and nucleophilic reagents

A simple and efficient stereoselective synthesis of fluoroalkyl substituted aziridine-2-phosphine oxides and -phosphonates by diastereoselective addition of methoxide, imidazole, benzenethiol, and Grignard reagents to functionalized ketoxime-phosphine oxides and -phosphonates is described. Aziridines are used as intermediates for the regioselective synthesis of fluorine containing beta-amino phosphine oxides and beta-amino phosphonates. Amino phosphorus derivatives can also be obtained from ketoximes derived from phosphine oxides and phosphonates with sodium borohydride.

Bisphosphonate inhibition of phosphoglycerate kinase: quantitative structure-activity relationship and pharmacophore modeling investigation

We report the results of a three-dimensional quantitative structure-activity relationship (3D-QSAR) and pharmacophore modeling investigation of the interaction of the enzyme 3-phosphoglycerate kinase (PGK) with aryl and alkyl bisphosphonates. For the human enzyme, the IC50 values are predicted within a factor of 2 over the 240x experimental range in activity, while for the yeast enzyme, binding of the more flexible alkyl bisphosphonates is predicted within a factor of approximately 4 (over a 2500x range in activity). Pharmacophore models indicate the importance of two negative ionizable features, one hydrophobic feature, and one halogen feature, and docking studies indicate that bisphosphonates bind in a manner similar to the 3-phosphoglycerate molecule identified crystallographically. The results give a good account of the activities of a diverse range of bisphosphonate inhibitors and are of interest in the context of developing inhibitors of glycolysis in organisms that are totally reliant on glycolysis for ATP production, such as trypanosomatid parasites.

Substrate-assisted movement of the catalytic Lys 215 during domain closure: site-directed mutagenesis studies of human 3-phosphoglycerate kinase

3-Phosphoglycerate kinase (PGK) is a two-domain hinge-bending enzyme. It is still unclear how the geometry of the active site is formed during domain closure and how the catalytic residues are brought into the optimal position for the reaction. Comparison of the three-dimensional structures in various open and closed conformations suggests a large (10 A) movement of Lys 215 during domain closure. This change would be required for direct participation of this side chain in both the catalyzed phospho transfer and the special anion-caused activation. To test the multiple roles of Lys 215, two mutants (K215A and K215R) were constructed from human PGK and characterized in enzyme kinetic and substrate binding studies. For comparison, mutants (R38A and R38K) of the known essential residue, Arg 38, were also produced. Drastic decreases (1500- and 500-fold, respectively), as in the case of R38A, were observed in the kcat values of mutants K215A and K215R, approving the essential catalytic role of Lys 215. In contrast, the R38K mutation caused an only 1.5-fold decrease in activity. This emphasizes the importance of a very precise positioning of Lys 215 in the active site, in addition to its positive charge. The side chain of Lys 215 is also responsible for the substrate and anion-dependent activation, since these properties are abolished upon mutation. Among the kinetic constants mainly the Km values of MgATP and 1,3-BPG are increased (approximately 20- and approximately 8-fold, respectively) in the case of the neutral K215A mutant, evidence of the interaction of Lys 215 with the transferring phospho group in the functioning complex. Weakening of MgATP binding (a moderate increase in Kd), but not of MgADP binding, upon mutation indicates an initial weak interaction of Lys 215 with the gamma-phosphate already in the nonfunctioning open conformation. Thus, during domain closure, Lys 215 possibly moves together with the transferring phosphate; meanwhile, this group is being positioned properly for catalysis.

Catalytic enantioselective fluorination and amination of beta-keto phosphonates catalyzed by chiral palladium complexes

[reaction: see text] The catalytic enantioselective fluorination and amination of beta-keto phosphonates catalyzed by chiral palladium complexes is described. Treatment of beta-keto phosphonates with N-fluorobenzenesulfonimide (NFSI) as electrophilic fluorinating reagent and diethyl azodicarboxylate (DEAD) as electrophilic amination reagent under mild reaction conditions afforded the corresponding alpha-substituted beta-keto phosphonates in moderate to excellent yields with excellent enantiomeric excesses.

Efficient synthesis of fluorothiosparfosic acid analogues with potential antitumoral activity

In this paper, we describe a short synthesis of N-(phosphonoacetyl)-L-aspartate (PALA) analogues. The mono- and difluorinated thioacetamide precursors were prepared in one step from methyl (diethoxyphosphono)di- and monofluoromethyldithioacetates 8 and 11 as starting materials. Antiproliferating properties on a L1210 strain and ATCase inhibition of these new compounds are disclosed. ThioPALA(FF) 5c showed a remarkable cytotoxic activity towards murine leukemia L1210, when used as tetraester.

Syntheses of ω-Hydroxy-α,α-difluoromethylphosphonates by Oxacycle Ring-Opening Reactions

[reaction: see text] Oxacycle ring-opening reactions from a non-HCFC-based source of phosphonodifluoromethyl carbanion 1 are reported. This straightforward strategy opens access to a variety of primary and secondary omega-hydroxy-alpha,alpha-difluoromethylphosphonates via one step. The syntheses of a glycerol monophosphate analogue and precursors to nucleoside phosphorylase inhibitors are described using this method.

Crystal structure of Trypanosoma cruzi glyceraldehyde-3-phosphate dehydrogenase complexed with an analogue of 1,3-bisphospho-d-glyceric acid

We report here the first crystal structure of a stable isosteric analogue of 1,3-bisphospho-d-glyceric acid (1,3-BPGA) bound to the catalytic domain of Trypanosoma cruzi glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH) in which the two phosphoryl moieties interact with Arg249. This complex possibly illustrates a step of the catalytic process by which Arg249 may induce compression of the product formed, allowing its expulsion from the active site. Structural modifications were introduced into this isosteric analogue and the respective inhibitory effects of the resulting diphosphorylated compounds on T. cruzi and Trypanosoma brucei gGAPDHs were investigated by enzymatic inhibition studies, fluorescence spectroscopy, site-directed mutagenesis, and molecular modelling. Despite the high homology between the two trypanomastid gGAPDHs (> 95%), we have identified specific interactions that could be used to design selective irreversible inhibitors against T. cruzi gGAPDH.

Orientation of 1,3-bisphosphoglycerate analogs bound to phosphoglycerate kinase

We have previously reported dissociation constants for a range of bisphosphonate analogs of 1,3-bisphospho-D-glyceric acid binding to yeast phosphoglycerate kinase. Data for the unsymmetrical analogs were difficult to interpret because it was not clear in which of the two possible orientations these ligands bound. Here we report a novel NMR method for quantifying orientation preference based on relaxation effects induced by titration with CrADP, which is applied to these ligands. It is shown that all ligands can bind in both orientations but that the driving force for the orientational preference is to put the alpha,alpha-difluoromethanephosphonate group in the "basic patch" (nontransferable phosphate) position. The relevance to the design of phosphoglycerate kinase inhibitors is discussed.

Selective inhibition of Trypanosoma brucei GAPDH by 1,3-bisphospho-D-glyceric acid (1,3-diPG) analogues

Various phosphono-phosphates and diphosphonates were synthesized as 1,3-diphosphoglycerate (1,3-diPG) analogues by using a beta-ketophosphonate, an alpha-fluoro,beta-ketophosphonate or a beta-ketophosphoramidate to mimic the unstable carboxyphosphate part of the natural substrate. The inhibitory effect of these analogues on glyceraldehyde-3-phosphate dehydrogenases (GAPDH) from Trypanosoma brucei (Tb) and rabbit muscle were measured with respect to both substrates, glyceraldehyde-3-phosphate (GAP) and 1,3-diPG. Interestingly, all 1,5-diphosphono,2-oxopentanes without substitution at the C-3 position selectively inhibit the Tb GAPDH with respect to 1,3-diPG and are without effect on Rm GAPDH. All 1-phospho,3-oxo,4-phosphonobutanes show themselves to be non-selective inhibitors either with regard to substrates or organisms, but they will be of a great interest as 1,3-diPG stable models for structural studies of co-crystals with GAPDHs.