Diethyl Phosphonate Research Articles

Synthesis of N9- and N7-[2-Hydroxy-3-(phosphonomethoxy)propyl] Derivatives of N6-Substituted Adenines, 2,6-Diaminopurines and Related Compounds

Base-catalyzed reactions of diethyl [(oxiranylmethoxy)methyl]phosphonate (2) with purine bases (adenine, 2,6-diaminopurine, 6-chloropurine and 2-amino-6-chloropurine) gave corresponding 9- or 7-[2-hydroxy-3-(phosphonomethoxy)propyl] purines. The adenine and 2,6-diaminopurine derivatives cyclize to cyclic phosphonates 4 and 6. The 9-[2-hydroxy-3-(phosphonomethoxy)propyl] derivatives of N6-substituted adenine and 2,6-diaminopurine (15-27) were prepared by the treatment of diethyl {[3-(6-chloropurin-9-yl)-2-hydroxypropoxy]methyl}phosphonate (11) or diethyl {[3-(2-amino-6-chloropurin-9-yl)-2-hydroxypropoxy]methyl}phosphonate (13) with primary or secondary amines. The reaction of 6-chloro- or 2-amino-6-chloropurine derivatives (11, 13) with thiourea gave the corresponding diethyl purine-6-thiol or 2-aminopurine-6-thiol phosphonates 47, 48. The guanine derivative 49 was prepared by the treatment of compound 13 with 80% acetic acid. All diethyl phosphonates were transformed to free phosphonic acids (31-43, 50-52) by the action of bromotrimethylsilane and subsequent hydrolysis.

Preparation of Diethyl 1-(Alkyl/Aryl-2-amino-4-oxo-4,5-dihydropyrrol-3-yl)phosphonates

The title compounds were prepared starting from diethyl (cyanomethyl)phosphonate by C-acylation with chloroacetyl chloride and subsequent amination with primary amines.

Porphyrins Bearing Mono or Tripodal Benzylphosphonic Acid Tethers for Attachment to Oxide Surfaces

The ability to attach redox-active molecules to oxide surfaces in controlled architectures (distance, orientation, packing density) is essential for the design of a variety of molecular-based information storage devices. We describe the synthesis of a series of redox-active molecules wherein each molecule bears a benzylphosphonic acid tether. The redox-active molecules include zinc porphyrins, a cobalt porphyrin, and a ferrocene-zinc porphyrin. An analogous tripodal tether has been prepared that is based on a tris[4-(dihydroxyphosphorylmethyl)phenyl]-derivatized methane. A zinc porphyrin is linked to the methane vertex by a 1,4-phenylene unit. The tripodal systems are designed to improve monolayer stability and ensure vertical orientation of the redox-active porphyrin on the electroactive surface. For comparison purposes, a zinc porphyrin bearing a hexylphosphonic acid tether also has been prepared. The synthetic approaches for introduction of the phosphonic acid group include derivatization of a bromoalkyl porphyrin or use of a dimethyl or diethyl phosphonate substituted precursor in a porphyrin-forming reaction. The latter approach makes use of dipyrromethane building blocks bearing mono or tripodal dialkyl phosphonate groups. The zinc porphyrin-tripodal compound bearing benzylphosphonic acid legs tethered to a SiO(2) surface (grown on doped Si) was electrically well-behaved and exhibited characteristic porphyrin oxidation/reduction waves. Collectively, a variety of porphyrinic molecules can now be prepared with tethers of different length, composition, and structure (mono or tripodal) for studies of molecular-based information storage on oxide surfaces.

An Efficient Separation Method for Enol Phosphate and Corresponding β‐Ketophosphonate from Their Mixtures under Aqueous Conditions.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Enzymatic resolution of 3-bromo-cyclohept-2-enol: application to the determination of the absolute configuration of diethyl (3-hydroxy-cyclohept-1-enyl)phosphonate

Enzymatic resolution of racemic 3-bromo-cyclohept-2-enol 2 with lipozyme affords enantiomerically pure ( S)-(−)- 2 whose absolute configuration was determined by chemical correlation, and further allowed an enantioselective synthesis of ( S)-(+)-diethyl (3-hydroxy-cyclohept-1-enyl)phosphonate 1.

Intramolecular Catalysis in Reactions of Hydroxamic Acids

Among hydroxamate ions (typical α nucleophiles), anomalously high nucleophilicity relative to 4-nitrophenyl diethyl phosphonate is seen in anions which have general basic catalytic sites that provide anchimeric assistance for proton transfer in the transition state.

11C-labeled stilbene derivatives as Aβ-aggregate-specific PET imaging agents for Alzheimer’s disease

A series of stilbene derivatives as potential diagnostic imaging agents targeting amyloid plaques in Alzheimer’s disease (AD) were synthesized and evaluated. The syntheses of the stilbenes were successfully achieved by a simple Wadsworth-Emmons reaction between diethyl (4-nitrobenzyl)phosphonate and 4-methoxybenzaldehyde. 4-N,N-dimethylamino-4′-methyoxy and the corresponding 4-N-monomethylamino-, 4′-hydroxy stilbenes showed good binding affinities towards Aβ aggregates in vitro (K i < 10 nM). The 11C labeled 4-N-methylamino-4′-hydroxystilbene, [ 11C]4, was prepared by 11C methylation of 4-amino-4′-hydroxystilbene. The [ 11C]4 displayed a moderate lipophilicity (log P = 2.36), and showed a very good brain penetration and washout from normal rat brain after an iv injection. In vitro autoradiography of transgenic AD mouse brain sections showed a high specific labeling of β-amyloid plaques, whereas the control sections showed no binding. Taken together the data suggest that a relatively simple stilbene derivative, [ 11C]4, N-[ 11C]methylamino-4′-hydroxystilbene, may be useful as a positron emission tomography (PET) imaging agent for mapping Aβ plaques in the brain of patients with Alzheimer’s disease.

An Efficient Separation Method for Enol Phosphate and Corresponding β-Ketophosphonate from Their Mixtures Under Aqueous Conditions

Separation of a mixture β-ketophosphonate 3 and their corresponding enol phosphate 4 is efficiently carried out in aqueous alkaline solutions. Enol phosphate 4 is first extracted with hexanes:dichloromethane (19:1). Acidification of the aqueous layer followed by extraction of the β-ketophosphonate 3 with dichloromethane completes the separation. Thus, when 1-bromo-2,4-pentadione 1a reacted with triethyl phosphite to give diethyl (2,4-dioxopentyl)phosphonate 3a (Arbuzov-product) and the corresponding enol phosphate 4a (Perkow-product), separation of the two compounds was carried out using this method.

Synthesis and copolymerization of new phosphorus‐containing acrylates

AbstractTwo phosphorus‐containing acrylate monomers were synthesized from the reaction of ethyl α‐chloromethyl acrylate and t‐butyl α‐bromomethyl acrylate with triethyl phosphite. The selective hydrolysis of the ethyl ester monomer with trimethylsilyl bromide (TMSBr) gave a phosphonic acid monomer. The attempted bulk polymerizations of the monomers at 57–60 °C with 2,2′‐azobisisobutyronitrile (AIBN) were unsuccessful; however, the monomers were copolymerized with methyl methacrylate (MMA) in bulk at 60 °C with AIBN. The resulting copolymers produced chars on burning, showing potential as flame‐retardant materials. Additionally, α‐(chloromethyl)acryloyl chloride (CMAC) was reacted with diethyl (hydroxymethyl)phosphonate to obtain a new monomer with identical ester and ether moieties. This monomer was hydrolyzed with TMSBr, homopolymerized, and copolymerized with MMA. The thermal stabilities of the copolymers increased with increasing amounts of the phosphonate monomer in the copolymers. A new route to highly reactive phosphorus‐containing acrylate monomers was developed. A new derivative of CMAC with mixed ester and ether groups was synthesized by substitution, first with diethyl (hydroxymethyl)phosphonate and then with sodium acetate. This monomer showed the highest reactivity and gave a crosslinked polymer. The incorporation of an ester group increased the rate of polymerization. The relative reactivities of the synthesized monomers in photopolymerizations were determined and compared with those of the other phosphorous‐containing acrylate monomers. Changing the monomer structure allowed control of the polymerization reactivity so that new phosphorus‐containing polymers with desirable properties could be obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2207–2217, 2003

Enzymatic resolution of diethyl (3-hydroxy-1-butenyl) phosphonate

The enzymatic esterification of diethyl (3-hydroxy-1-butenyl) phosphonate 1 with different enzymes has been carried out, and allows the preparation of (S)-1 and (R)-diethyl (3-acetoxy-1-butenyl) phosphonate 2 with very high enantiomeric excess. The absolute conguration of 1 was determined by independent synthesis from (S)-ethyl lactate.

A Convenient Synthesis of Dibenzyl α,α-Difluoromethyl-β-ketophosphonates

The first synthesis of dibenzyl α,α-difluoro-β-ketophosphonates has been accomplished by an original fluorination reaction, namely addition of the F+ ion to the enolate form of the corresponding dibenzyl β-ketophosphonate. After an easy cleavage of the benzyloxy protecting groups on the phosphorus atom, α-fluoro-β-ketophosphonic acids were subsequently obtained as stable carboxyphosphate mimics. This approach enables α,α-difluoro-β-ketophosphonate moieties to be introduced into multiply functionalised molecules, thus making the previously described diethyl phosphonate route no longer relevant. Moreover, study of their stability under neutral and basic conditions showed the importance of the keto-enol equilibrium in the decomposition pathway of these molecules. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

PhosphonateO-Deethylation of [4-(4-Bromo-2-Cyano-Phenylcarbamoyl) Benzyl]-Phosphonic Acid Diethyl Ester, a Lipoprotein Lipase-Promoting Agent, Catalyzed by Cytochrome P450 2C8 and 3A4 in Human Liver Microsomes

NO-1886 ([4-(4-bromo-2-cyano-phenylcarbamoyl) benzyl]-phosphonic acid diethyl ester) increases lipoprotein lipase activity, resulting in a reduction in plasma triglycerides and an increase in high-density lipoprotein cholesterol. The metabolism of NO-1886 in human liver was investigated in the present study. Ester cleavage of NO-1886 from diethyl phosphonate to monoethyl phosphonate was the major metabolic pathway catalyzed by cytochrome P450. In addition, the minor metabolic pathway in human liver was the hydrolysis of the amide bond of NO-1886 by a specific cytosolic esterase. Eadie-Hofstee plots of phosphonate O-deethylation of NO-1886 in human liver microsomes showed a biphasic curve, indicating low- and high-K(m) components. Inhibition experiments with chemical inhibitors and antibodies against various cytochrome P450 isoforms suggested the involvement of CYP2C8 and CYP3A in the phosphonate O-deethylation. Recombinant CYP3A4 and CYP2C8 expressed in baculovirus-infected insect cells and human lymphoblastoid cells exhibited a high activity for phosphonate O-deethylation of NO-1886. The recombinant cytochrome P450 enzymes indicated that CYP2C8 and CYP3A4 were responsible for the low- and high-K(m) components in human liver microsomes, respectively. The selectivity of CYP2C8 in catalyzing phosphonate O-deethylation indicates that coadministration of drugs that are metabolized by the same enzyme requires careful consideration.

Studies of the hydrolysis of ethyl and tert-butyl phosphonates covalently bonded to silica xerogels

The mild cleavage of phosphonodiester groups supported on a silica matrix has been investigated. The use of TMSBr (bromotrimethylsilane) with diethyl phosphonates has been revisited, and interactions of phosphonoacids with silicon species are described. An alternative route utilising di-tert-butyl phosphonate group has also been studied and in this case cleavage has been demonstrated in very mild conditions.

A general synthesis of ethyl 4-aminophenyl and ethyl 4-[amino(hydroxyimino)methyl]phenyl phosphonates

Diethyl phosphonates were conveniently converted into ethyl 4-aminophenyl and ethyl 4-[amino(hydroxyimino)methyl]phenyl phosphonates as potentially useful intermediates for the preparation of functionalized phenyl phosphonates.

Flame retardance of poly(methyl methacrylate) modified with phosphorus-containing compounds

MMA has been copolymerised with pentavalent phosphorus-containing monomers and the flame retardance of the resulting copolymers has been assessed by limiting oxygen indicies (LOI) and cone calorimetry experiments. The thermal stability of the copolymers has also been assessed by conventional thermogravimetric analysis (TGA). Poly(methyl methacrylate) (PMMA) modified with phosphorus-containing additives have also been synthesised and the flame retardance assessed. All of the modified PMMA samples contain 3.5 wt.%, allowing a comparison of the relative merits of an additive and a reactive approach to flame retardance. The chemical environment of the phosphorus in terms of flame retardance achieved is also considered in this paper. The incorporation of 3.5 wt.% phosphorus in both reactive and additive approaches increases the limiting oxygen index of PMMA from 17.8 to over 21. However, cone calorimetry shows that the phosphorus-containing copolymers are inherently more flame retardant than PMMA and the PMMA modified with phosphorus-containing additives. The methyl methacrylate (MMA) copolymers have significantly reduced peak rates of heat release and leave substantial char residue during combustion, as compared to PMMA. Cone calorimetry has also shown that the phosphates are more effective flame-retardants for PMMA than are the phosphonates in both additive and reactive approaches. TGA of the polymers indicates that the copolymers are more thermally stable than PMMA whilst PMMA containing the additives are less thermally stable. A condensed phase mechanism in which diethyl(methacryloyloxymethyl)phosphonate reduces the flammability of PMMA has been identified.

Synthesis of New Phosphines and P-Heterocycles from Phosphonates Containing Allyl Group

Addition of phenylphosphine to allylphosphonate followed by reduction of the resulting diphosphonate gives a new branched phosphine, bis(3-phosphinopropyl)phenylphosphine. Its reaction with paraform and p-toluidine yields oligomeric 3-[3-(propylenophenylphosphino)propyl]-1,5-di-p-tolyl-1,5,3,7-diazadiphosphacyclooctane. Diethyl (5-allyl-2-ethoxybenzyl)phosphonate was obtained. Its reduction gives unsaturated (5-allyl-2-ethoxybenzyl)phosphine. This product adds two moles of formaldehyde to give bis(hydroxymethyl)(5-allyl-2-ethoxybenzyl)phosphine. The reaction of this compound with p-toluidine yielded, depending on the conditions, the corresponding bis(aminomethyl)phosphine, 1,3,5-diazaphosphorinane, and 1,5,3,7-diazadiphosphacyclooctane, and also their derivatives containing allyl substituents.

ACYCLIC NUCLEOSIDE/NUCLEOTIDE ANALOGUES WITH AN IMIDAZOLE RING SKELETON

Syntheses of a few acyclic nucleoside and acyclic nucleoside phosphonate analogues containing an imidazole ring have been reported. These analogues include methyl 1-(2-hydroxyethoxymethyl)imidazole-4,5-dicarbo-xylate (1), 4,5-dicarbamoyl-1-(2-hydroxyethoxymethyl)imidazole (2), 4,5-dicya-no-1-(2-hydroxyethoxymethyl)imidazole (4), Methyl 1-(2-bromoethoxymethyl)- imidazole-4,5-dicarboxylate (7), 4,5-dicyano-(2-bromoethoxymethyl)imidazole (8), and Methyl 1-(2-phosphonomethoxyethyl)imidazole (10). Also reported are a few potential prodrugs of the above compounds, including the acetyl derivatives 5 and 6 (of 1 and 4, respectively), and the diethyl phosphonate ester 9 (of 10). In addition, the corresponding benzyl-protected precursors 11 and 12 (of 1 and 4, respectively), along with their common hydrolysis product, 1-(2-benzyloxy-ethoxymethyl)-4,5-imidazoledicarboxylic acid (3), are reported. Another potential prodrug included in the list is 1-(2-acetoxyethyl)-4,5-dicyanoimidazole (15). The compounds were screened for in vitro antiviral activity against a wide variety of herpes and respiratory viruses. The most active compound was the phosphonate analogue 9 which exhibited an anti-measles virus activity with an EC50 of <2.5 μg/mL and an SI value of > 176.

A convergent triflate displacement approach to (alpha-monofluoroalkyl)phosphonates.

[reaction: see text] Treatment of primary alkyl triflates or iodides with the potassium salt of diethyl (alpha-fluoro-alpha-phenylsulfonylmethyl)phosphonate yields (alpha-fluoro-alpha-phenylsulfonylalkyl)phosphonates. These can be cleanly desulfonated, in a matter of minutes, with Na(Hg) in MeOH/THF/NaH(2)PO(4). This two-step procedure complements previously reported triflate displacement approaches to alpha-nonfluorinated and alpha,alpha-difluorinated phosphonates.

DEALKYLATION OF PHOSPHONATE ESTERS WITH CHLOROTRIMETHYLSILANE

Chlorotrimethylsilane completely dealkylates phosphonate esters at elevated temperature in a sealed reaction vessel. These conditions are tolerated by a variety of functional groups and lead to high conversions of dimethyl, diethyl and diisopropyl phosphonates to their corresponding phosphonic acids.

Use of Diethyl(2-methylpyrrolidin-2-yl)phosphonate as a Highly Sensitive Extra- and Intracellular 31P NMR pH Indicator in Isolated Organs: DIRECT NMR EVIDENCE OF ACIDIC COMPARTMENTS IN THE ISCHEMIC AND REPERFUSED RAT LIVER

The novel phosphorylated pyrrolidine diethyl(2-methylpyrrolidin-2-yl)phosphonate (DEPMPH) was evaluated as a (31)P NMR probe of the pH changes associated with ischemia/reperfusion of rat isolated hearts and livers. In vitro titration curves indicated that DEPMPH exhibited a 4-fold larger amplitude of chemical shift variation than inorganic phosphate yielding an enhanced NMR sensitivity in the pH range of 5.0-7.5 that allowed us to assess pH variations of less than 0.1 pH units. At the non-toxic concentration of 5 mm, DEPMPH distributed into external and cytosolic compartments in both normoxic organs, as assessed by the appearance of two resonance peaks. An additional peak was observed in normoxic and ischemic livers, assigned to DEPMPH in acidic vesicles (pH 5.3-5.6). During severe myocardial ischemia, a third peak corresponding to DEPMPH located in ventricular and atrial cavities appeared (pH 6.9). Mass spectrometry and NMR analyses of perchloric extracts showed that no significant metabolism of DEPMPH occurred in the ischemic liver. Reperfusion with plain buffer resulted in a rapid washout of DEPMPH from both organs. It was concluded that the highly pH-sensitive DEPMPH could be of great interest in noninvasive ex vivo studies of pH gradients that may be involved in many pathological processes.