Rapid, mild method for phosphonate diester hydrolysis: development of a one-pot synthesis of tenofovir disoproxil fumarate from tenofovir diethyl ester

Drug Discovery and Exploration of Heterocycles for the Development of Anti-HIV Agents

It is a known fact that HIV infection remains a serious public health problem throughout the world, and the need to constantly develop new antiretroviral drugs to combat HIV emerges from the fact that repetitive mutations occurring in viral enzymes make this virus resistant to antiretroviral drugs. This resistance causes failure of treatment, and hence, for many years, extensive research has been to discover newer possibilities for fighting this disease at a molecular level, along with many long-standing and expensive clinical trials. Many scientific research programs have either been discarded or unsuccessful. However, the research has not stopped, and in the process, many heterocyclic scaffolds have been used to build up novel drug molecules to combat this disease. A literature survey reveals that many heterocycles have been explored and were found to be very useful in treating different types of viral infections. This concise and rigorous literature explains the journey and highlights the various strategies to develop new anti-HIV drug candidates.

One-Pot Synthesis of Bioinspired Peptide-Decorated Apatite Nanoparticles for Nanomedicine

Hybrid organic-inorganic bio-inspired apatite nanoparticles (NPs) are attractive for biomedical applications and especially in nanomedicine. Unfortunately, their applications in nanomedicine are limited by their broad particle size distributions and uncontrolled drug loading due to their multistep synthesis process.  Besides, very few attempts at exposing bioactive peptides on apatite NPs are made. In this work, an original one-pot synthesis of well-defined bioactive hybrid NPs composed of a mineral core of bioinspired apatite surrounded by an organic corona of bioactive peptides is reported. Dual stabilizing-bioactive agents, phosphonated polyethylene glycol-peptide conjugates, are prepared and directly used during apatite precipitation i) to form the organic corona during apatite precipitation, driving the size and shape of resulting hybrid NPs with colloidal stabilization and ii) to expose peptide moieties (RGD or YIGSR sequences) at the NPs periphery in view of conferring additional surface properties to enhance their interaction with cells. Here, the success of this approach is demonstrated, the functionalized NPs are fully characterized by Fourier-transform infrared, Raman, X-ray diffraction, solid and liquid state NMR, transmission electron microscopy, and dynamic light scattering, and their interaction with fibroblast cells is followed, unveiling a synergistic proliferative effect.

The Hydrolysis of Phosphinates and Phosphonates: A Review

Phosphinic and phosphonic acids are useful intermediates and biologically active compounds which may be prepared from their esters, phosphinates and phosphonates, respectively, by hydrolysis or dealkylation. The hydrolysis may take place both under acidic and basic conditions, but the C-O bond may also be cleaved by trimethylsilyl halides. The hydrolysis of P-esters is a challenging task because, in most cases, the optimized reaction conditions have not yet been explored. Despite the importance of the hydrolysis of P-esters, this field has not yet been fully surveyed. In order to fill this gap, examples of acidic and alkaline hydrolysis, as well as the dealkylation of phosphinates and phosphonates, are summarized in this review.

Sustainability and some green initiatives in undergraduate education

Green Chemistry is also known as sustainable chemistry or benign chemistry. It is concerned with developing processes and products that reduce or eliminate the use of and generation of hazardous substances. In the 21st century today’s students are particularly interested in matters that affect their health and well-being of the planet. To deal with such challenges of students the concept of Green and Sustainable Chemistry not only offers an excellent opportunity to address some of these concerns, but also provides us with a useful way to advance the way we do chemistry. Green chemistry is an ideal focus for undergraduate science education. A strong laboratory component is at the heart of many science courses. In this chapter some of the green chemistry principles and methodologies used to device certain undergraduate laboratory experiments and research are discussed.

An improved synthesis of adefovir and related analogues

An improved synthesis of the antiviral drug adefovir is presented. Problems associated with current routes to adefovir include capricious yields and a reliance on problematic reagents and solvents, such as magnesium tert-butoxide and DMF, to achieve high conversions to the target. A systematic study within our laboratory led to the identification of an iodide reagent which affords higher yields than previous approaches and allows for reactions to be conducted up to 10 g in scale under milder conditions. The use of a novel tetrabutylammonium salt of adenine facilitates alkylations in solvents other than DMF. Additionally, we have investigated how regioselectivity is affected by the substitution pattern of the nucleobase. Finally, this chemistry was successfully applied to the synthesis of several new adefovir analogues, highlighting the versatility of our approach.

A LC/MS/MS method for determination of tenofovir in human plasma and its application to toxicity monitoring

Tenofovir disoproxil fumarate is a pro-drug of the active metabolite tenofovir widely used against the HIV1, HIV2, and Hepatitis B virus. Several studies have been conducted and found kidney injury associated with tenofovir exposure. High tenofovir plasma concentration correlated with kidney injury in tenofovir-exposed patients. The present study developed and validated a simple and cost-effective LC/MS/MS method to determine tenofovir level in human plasma. A small plasma volume of 80 μl is utilized for the sample preparation. The samples were separated by Luna C18 (100 mm × 2.0 mm, 3 μm) using gradient elution with a mobile phase consisting of water (containing 0.1% formic acid) and acetonitrile (90:10, v/v). The detection was achieved through multiple reaction monitoring using positive ionization mode on the triple quadrupole mass spectrometer with a run time of 10 min. The monitoring transitions were set at m/z 288.0 → 176.1 and 136.1 for tenofovir and m/z 226.1 → 152.0 for acyclovir (as the internal standard). This standard curve was linear from 10 to 640 ng/ml, with the lower limit of quantification of 10 ng/ml. The inter- and intra-day precision results were less than 12.3% and their accuracies were within the acceptable range of 84.9-113.1%. The validated method was successfully applied to the study of tenofovir induced kidney injury in HIV-1 infected patients taking 300 mg once daily for more than 4 weeks.

Directly Coupled Versus Spectator Linkers on Diimine PtII Acetylides-Change the Structure, Keep the Function?

Modification of light-harvesting units with anchoring groups for surface attachment often compromises light-harnessing properties. Herein, a series of [donor-acceptor-anchor] platinum(II) diimine (bis-)acetylides was developed in order to systematically compare the effect of conjugated versus electronically decoupled modes of attachment of protected anchoring groups on the photophysical properties of light-harvesting units. The first examples of "decoupled" phosphonate diimine Pt^II complexes are reported, and their properties are compared and contrasted to those of carboxylate analogues studied by a diversity of methods. Ultrafast time-resolved IR and transient absorption spectroscopy revealed that all complexes have a charge-transfer (CT) lowest excited state with lifetimes between 2 and 14 ns. Vibrational signatures and dynamics of CT states were identified; the assignment of electronic states and their vibrational origin was aided by TDDFT calculations. Ultrafast energy redistribution accompanied by structural changes was directly captured in the CT states. A significant difference between the structures of the electronic ground and CT excited states, as well as differences in the structural reorganisation in the complexes bearing directly attached or electronically decoupled anchoring groups, was discovered. This work demonstrates that decoupling of the anchoring group from the light-harvesting core by a saturated spacer is an easy approach to combine surface attachment with high reduction potential and ten times longer lifetime of the CT excited state of the light-absorbing unit, and retain electron-transfer photoreactivity essential for light-harvesting applications.

Fluorinated matrix metalloproteinases inhibitors--Phosphonate based potential probes for positron emission tomography

Fluorine-containing inhibitors of matrix metalloproteinases (MMPs) can serve as lead structures for the development of (18)F-labeled radioligands. These compounds might be useful as non-invasive imaging probes to characterize pathologies associated with increased MMP activity. Results with a series of fluorinated analogs of a known biphenyl sulfonamide inhibitor have shown that fluorine can be incorporated into two different positions of the molecular scaffold without significant loss of potency in the nanomolar range. Additionally, the potential of a hitherto unknown fluorinated tertiary sulfonamide as MMP inhibitor has been demonstrated.

Component mobility by a minute quantity of the appropriate solvent as a principal motif in the acceleration of solid-supported reactions

The effects solvents have on fluoride-promoted heterogeneous hydrolysis and alcoholysis of various organo-phosphorus (OP) compounds on the surface of KF/Al2O3 are described. Solid-state magic angle spinning NMR analyses and SEM microscopy have shown that not only is the identity of the solvent important in these reactions but also its quantity. That is, minimal solvent amounts are favored and much more effective in such solid-supported reactions (and maybe generally) than those featuring solvent-free or excess solvent (>50 wt %) conditions. The addition of a minute quantity of the correct solvent (3-10 wt %, molar equivalent scale) avoids reagents leaching from the matrix, permits mobility (mass transport) of the reaction components and ensures their very high local concentration in close proximity to the solid-support large porous surface area. Accordingly, significant acceleration of reactions rates by orders of magnitude is obtained. Fascinatingly, even challenging phosphoesters with poor leaving groups, which were found to be very stable in the presence of solvent-free KF/Al2O3 or wetted with excess water, were efficiently hydrolyzed with a minute amount of this solvent.

Synthesis, characterization and selective de-esterification of diorganotinbis(O-methylphosphite)s

A one-pot reaction between di-n-butyl/diethyl/dimethyltin dichloride and dimethylphosphite (MeO)2P(O)H in a solvent free medium (120 °C, 18 h) proceeds smoothly to yield the corresponding diorganotinbis(O-methylphosphite)s, [R2Sn(OP(O)(OMe)H)2]n [R = n-Bu (1), Et (2), Me (3)]. The identity of 1-3 has been established by IR, multinuclear ((1)H, (13)C, (31)P, (119)Sn) NMR, powder X-ray diffraction (PXRD) and X-ray crystallography. The coordination framework in each case adopts a one-dimensional structural motif comprising an infinite array of eight-membered [Sn-O-P-O]2 cyclic rings, with the phosphite ligands acting in a bridging bidentate mode. The structures are extended to two- (for 1) and three-dimensional (for 2, 3) assemblies by virtue of C-H···O hydrogen bonding interactions. The stability and bulk properties of 1-3 have been investigated upon exposure to humid laboratory conditions using (1)H NMR, PXRD and SEM studies. The results conform to a unique chemical modification of 1-3 involving selective de-esterification of P-OMe bonds and the formation of corresponding diorganotinbis(phosphite)s, [R2Sn(OP(O)(OH)H)2]n (1a-3a), as insoluble solids. The results obtained from impedance studies (σ = 10(-4)-10(-6) S cm(-1); E(a) = 0.33-0.42 eV) reveal potential application of 1a-3a as proton conducting materials.

Ester prodrugs of acyclic nucleoside thiophosphonates compared to phosphonates: synthesis, antiviral activity and decomposition study

9-[2-(Thiophosphonomethoxy)ethyl]adenine [S-PMEA, 8] and (R)-9-[2-(Thiophosphonomethoxy)propyl]adenine [S-PMPA, 9] are acyclic nucleoside thiophosphonates we described recently that display the same antiviral spectrum (DNA viruses) as approved and potent phosphonates PMEA and (R)-PMPA. Here, we describe the synthesis, antiviral activities in infected cell cultures and decomposition study of bis(pivaloyloxymethoxy)-S-PMEA [Bis-POM-S-PMEA, 13] and bis(isopropyloxymethylcarbonyl)-S-PMPA [Bis-POC-S-PMPA, 14] as orally bioavailable prodrugs of the S-PMEA 8 and S-PMPA 9, in comparison to the equivalent "non-thio" derivatives [Bis-POM-PMEA, 11] and [Bis-POC-PMPA, 12]. Compounds 11, 12, 13 and 14 were evaluated for their in vitro antiviral activity against HIV-1-, HIV-2-, HBV- and a broad panel of DNA viruses, and found to exhibit moderate to potent antiviral activity. In order to determine the decomposition pathway of the prodrugs 11, 12, 13 and 14 into parent compounds PMEA, PMPA, 8 and 9, kinetic data and decomposition pathways in several media are presented. As expected, bis-POM-S-PMEA 13 and bis-POC-S-PMPA 14 behaved as prodrugs of S-PMEA 8 and S-PMPA 9. However, thiophosphonates 8 and 9 were released very smoothly in cell extracts, in contrast to the release of PMEA and PMPA from "non-thio" prodrugs 11 and 12.