Novel hydroxyphosphonate inhibitors of CD-45 tyrosine phosphatase

Unexpected Reaction of Dialkyl α-Hydroxy-benzylphosphonates with Dialkyl Phosphites and a Few Related Reactions

The condensation of dialkyl α-hydroxy-benzylphosphonates with dialkyl phosphites and that of α-hydroxybenzyl-diphenylphosphine oxide with diphenylphosphine oxide unexpectedly gave the corresponding phosphorylated α-hydroxy derivatives. This new reaction proved to be general. The formation of the two products may be similar and involves the attack of the hydroxy group of the α-hydroxyphosphonate or α-hydroxyphosphine oxide on the phosphorus atom of the trivalent tautomer form (Y2POH) of the Y2P(O)H reagent (Y= MeO, EtO, or Ph) going with the elimination of an alcohol and water molecule, respectively. The mechanism was supported by DFT computations at the M062X/6-31G (d,p) level of theory, including suitable proton transfer networks. The condensations discussed are typical autocatalytic reactions promoted by the alcohol or water molecules formed. The initial promoters are the traces of water inevitably present in the mixture. In the reaction of α-hydroxyphosphonates with dialkyl phosphites, the -P(O)(OR)H derivative is the primary product that is partially hydrolyzed to the -P(O)(OH)H species by the traces of water under the conditions of the reaction. Arbuzov reaction of diethyl α-bromobenzylphosphonate with ethyl diphenyphosphinite afforded the target-like phenylmethylene-phosphine oxide─phosphonate derivative.

Synthesis of non-racemic α-hydroxyphosphonates via asymmetric phospho-aldol reaction

It has been more than 50 years since the first phospho-aldol reactions of dialkyl phosphites were reported. These efficient P-C bond-forming reactions have become the cornerstone of methods for the synthesis of α-hydroxyphosphonates and, by numerous available substitution reactions, the synthesis of other α- and γ-substituted phosphonates and phosphonic acids. Much of the interest in α- and γ-substituted phosphonates and phosphonic acids has been stimulated by reports of their biological activity, which is often dependent upon their absolute and relative stereochemistry. In this chapter, we review diastereoselective and enantioselective additions of dialkyl phosphites to aldehydes and ketones, otherwise called the phospho-aldol, Pudovik or Abramov reactions.

Nano-rod ZnO as a novel and reusable catalyst for C−P bond formation and hydrophosphonation of isatin derivatives under solvent-free conditions

A highly efficient method for the synthesis of α1-oxindole-α-hydroxyphosphonates via nano-rod ZnO catalyzed hydrophosphonation of isatin derivatives was developed. The reaction products are in excellent yields using the catalytic system nano-rod ZnO (25 mol%) under solvent-free conditions at room temperature. The catalyst can be reused several times without any significant loss of its activity.

Diastereoisomeric macrocyclic polydisulfides from the mangrove Bruguiera gymnorrhiza

The uncommon macrocyclic polydisulfides, trans-3,3'-dihydroxy-1,5,1',5'-tetrathiacyclodecane (1), cis-3,3'-dihydroxy-1,5,1',5'-tetrathiacyclodecane (2), along with five known related cyclic disulfides, gymnorrhizol (3), neogymnorrhizol (4), bruguiesulfurol (5), brugierol (6), and isobrugierol (7), were isolated from the mangrove Bruguiera gymnorrhiza collected from Guangdong Province, China. Structures of compounds 1 and 2 were determined by extensive analysis of their spectroscopic data, by comparison of their NMR spectroscopic data with those of the co-occurring known compounds, as well as by single-crystal X-ray diffraction analysis. A possible biogenetic origin was also proposed.

Surface-enhanced Raman scattering studies on the interaction of phosphonate derivatives of imidazole, thiazole, and pyridine with a silver electrode in aqueous solution

Surface-enhanced Raman scattering (SERS) spectra from phosphonate derivatives of N-heterocyclic aromatic compounds immobilized on an electrochemically roughened silver electrode surface are reported and compared to Raman spectra of the corresponding solid species. The tested compounds contain imidazole [ImMeP ([hydroxy-(1H-imidazol-5-yl)-methyl]-phosphonic acid) and (ImMe)2P (bis[hydroxy-(1H-imidazol-4-yl)-methyl]-phosphinic acid)]; thiazole [BAThMeP ((butylamino-thiazol-2-yl-methyl)-phosphonic acid) and BzAThMeP ((benzylamino-thiazol-2-yl-methyl)-phosphonic acid)]; and pyridine ((PyMe)2P (bis[(hydroxy-pyridin-3-yl-methyl)]-phosphinic acid) aromatic rings. Changes in wavenumber, broadness, and the enhancement of N-heterocyclic aromatic ring bands upon adsorption are consistent with the adsorption primarily occurring through the N lone pair of electrons with the ring arranged in a largely edge-on manner for ImMeP and BzAThMeP or in a slightly inclined orientation to the silver electrode surface at an intermediate angle from the surface normal for (ImMe)2P, BAThMeP, and (PyMe)2P. A strong enhancement of a roughly 1500 cm(-1) SERS signal for ImMeP and (PyMe)2P is also observed. This phenomenon is attributed to the formation of a localized C=C bond, which is accompanied by a decrease in the ring-surface pi-electrons' overlap. In addition, more intense SERS bands due to the benzene ring in BzAThMeP are observed than those observed for the thiazole ring, which suggests a preferential adsorption of benzene. Some interaction of a phosphonate unit is also suggested but with moderate strength between biomolecules. The strength of the P=O coordination to the silver electrode is highest for ImMeP but lowest for BzAThMeP. For all studied biomolecules, the contribution of the structural components to their ability to interact with their receptors was correlated with the SERS patterns.

Vanillic acid derivatives from the green algae Cladophora socialis as potent protein tyrosine phosphatase 1B inhibitors

A novel vanillic acid derivative (1) and its sulfate adduct (2) were isolated from a green algae, Cladophora socialis. The structures of 1 and 2 were elucidated from NMR and HRESIMS experiments. Both compounds showed potent inhibitory activity against protein tyrosine phosphatase 1B (PTP1B), an enzyme involved in the regulation of insulin cell signaling. Compounds 1 and 2 had IC50 values of 3.7 and 1.7 microM, respectively.

Synthesis and in vitro evaluation of S-acyl-3-thiopropyl prodrugs of Foscarnet

A new enzyme-labile group called S-acyl-3-thiopropyl group (SATP) has been synthesized from allylic esters of phosphonate. After demonstration of the enzyme-labile character of the SATP in cellular extracts, it has been introduced onto the phosphonate moiety of PFA (Foscarnet) to obtain potential lipophilic prodrugs. To ponder the lipophilicity of the triesters of PFA, esters of monomethylether of polyethyleneglycols and of thioglycerol were introduced on the PFA carboxylate moiety. The SATP groups were introduced in an attempt to deliver PFA after bioactivation inside the cells. The PFA prodrugs were evaluated in vitro for their activity against human immunodeficiency viruses (HIV-1 and HIV-2).

Solid-Phase Synthesis of an Oxalic Acid Amide Library

Monoamides of oxalic acid are of interest as bioisosteric replacements for phosphate groups in the design of new enzyme inhibitors. Here, we have demonstrated the use of oxalic acid as a linker to the Wang resin to synthesize individual or libraries of phosphate biosteres. The highly reactive resin-bound acid chloride reacts with arylamines to yield resin-bound N-aryloxamic acids (oxanilic acids). This methodology is especially useful for the rapid synthesis of 2-(oxalylamino)benzoic acids (OBAs), because it can be utilized for library synthesis and eliminates the intermediate purification step necessary in solution-phase reactions. The products are cleaved off the resin with trifluoroacetic acid in dichloromethane in good yields.

Chiral liquid chromatography separation and chiroptical properties of the enantiomers of dimethyl alpha-hydroxyfarnesylphosphonate, a precursor of a farnesyl protein transferase inhibitor

The HPLC enantiomeric separation of racemic and non-racemic samples of dimethyl alpha-hydroxyfarnesylphosphonate (1) was accomplished using Chiralcel OD as chiral stationary phase. Single enantiomers were isolated by semipreparative HPLC and their CD spectra and optical rotations were measured. The method ascertains enantiomeric excess of 1, obtained by oxidation of dimethylfarnesylphosphonate with enantiopure oxaziridines, avoiding converting the enantiomers to diastereomers by the use of a chiral auxiliary. Stability of the solutions of 1 is strongly dependent on the nature of the solvent.

Small ligands interacting with the phosphotyrosine binding pocket of the Src SH2 protein

Various small fragments bearing phosphate, phosphonate or phosphonic acid moieties have been prepared through parallel synthesis and their binding potencies evaluated on the Src SH2 protein using a BIAcore assay. This provided us insight into the requirement of the Src SH2 pTyr binding pocket and some promising small ligands have been characterised.

Toward antibody-catalyzed hydrolysis of organophosphorus poisons

We report here our preliminary results on the use of catalytic antibodies as an approach to neutralizing organophosphorus chemical weapons. A first-generation hapten, methyl-alpha-hydroxyphosphinate Ha, was designed to mimic the approach of an incoming water molecule for the hydrolysis of exceedingly toxic methylphosphonothioate VX (1a). A moderate protective activity was first observed on polyclonal antibodies raised against Ha. The results were further confirmed by using a mAb PAR 15 raised against phenyl-alpha-hydroxyphosphinate Hb, which catalyzes the hydrolysis of PhX (1b), a less toxic phenylphosphonothioate analog of VX with a rate constant of 0.36 M(-1) x min(-1) at pH 7.4 and 25 degrees C, which corresponds to a catalytic proficiency of 14,400 M(-1) toward the rate constant for the uncatalyzed hydrolysis of 1b. This is a demonstration on the organophosphorus poisons themselves that mAbs can catalytically hydrolyze nerve agents, and a significant step toward the production of therapeutically active abzymes to treat poisoning by warfare agents.

Solid-phase synthesis of potential protein tyrosine phosphatase inhibitors via the Ugi four-component condensation

A library of 108 alpha,alpha-difluoromethylenephosphonic acids was prepared by Ugi four-component condensation using Rink-NH2 resin, 4-[(diethoxyphosphinyl) difluoromethyl]benzoic acid, and a set of 18 aldehydes and 6 isonitriles. Following resin cleavage, the diethylphosphonate esters were hydrolyzed with trimethylsilyl bromide to yield the free acids which were assayed for inhibition of PTP alpha, PTP beta and PTP epsilon.

Potent non-peptidyl inhibitors of protein tyrosine phosphatase 1B

The development of inhibitors of protein tyrosine phosphatases (PTPs) has recently been the subject of intensive investigation due to their potential as chemotherapeutics and as tools for studying signal transduction pathways. Here we report the evaluation of a variety of small molecule, non-peptidyl inhibitors of protein tyrosine phosphatase 1B (PTP1B), bearing the alpha, alpha-difluoromethylenephosphonic acid (DFMP) group, a non-hydrolyzable phosphate mimetic. A series of phenyl derivatives bearing a single DFMP group were initially surveyed. In general, these were not significantly more potent inhibitors than the parent compound, alpha, alpha-difluorobenzylphosphonic acid, with the exception being the meta-phenyl substituted species which decreased the IC50 by approximately 17-fold relative to alpha, alpha-difluorobenzylphosphonic acid. However, certain compounds bearing two DFMP moieties were very potent inhibitors. Some of these are among the most potent small molecule inhibitors of any PTP reported to date with the best one exhibiting a Ki of 1.5 microM. The structural basis for these results are discussed. One of the bis-DFMP inhibitors was examined in detail and it was found that the fluorines were essential for potent inhibition. Inhibition was independent of pH between pH 5.5-7.2 suggesting that both the mono and dianionic forms of the individual DFMP groups bind equally well. The trends observed in the inhibitory potency of these compounds with PTP1B were very similar to the trends observed by other workers on the K(m)'s of the analogous phenylphosphate substrates with rat PTP1. This indicates that studies of non-peptidyl substrates with rat PTP1 can be used as a guide for the development of human PTP1B inhibitors.