Petri A. Turhanen

Bisphosphonate prodrugs : synthesis and in vitro evaluation of alkyl and acyloxymethyl esters of etidronic acid as bioreversible prodrugs of etidronate

The synthesis and preliminary evaluation of novel alkyl and acyloxymethyl esters of etidronic acid as etidronate prodrugs is reported. Tetramethyl ester of etidronic acid was found be isomerized at pH 7.4 and P-C-P bridge was rearranged to P-C-O-P. This unwanted process was prevented via acylation of the bridging carbons alcohol group. Acylation showed to be stable if one or more phosphonic OH- groups were substituted. However, when none of the phosphonic OH- groups were substituted, the acylation was chemically hydrolysed and the parent drug was released. This finding was successfully applied in the design of tetrapivaloyloxymethyl ester of acetylated etidronic acid which released etidronic acid via enzymatic (first step) and chemical (second step) hydrolysis in liver homogenate. However, the corresponding tri-substituted pivaloyloxymethyl ester having adequate water-solubility and lipophilicity (logP(app) 0.6 at pH 7.4), is probably the most potential prodrug candidate reported to enhance the oral bioavailability of etidronate.

Advanced material and approach for metal ions removal from aqueous solutions

A Novel approach to remove metals from aqueous solutions has been developed. The method is based on a resin free, solid, non-toxic, microcrystalline bisphosphonate material, which has very low solubility in water (59 mg/l to ion free Milli-Q water and 13 mg/l to 3.5% NaCl solution). The material has been produced almost quantitatively on a 1 kg scale (it has been prepared also on a pilot scale, ca. 7 kg) and tested successfully for its ability to collect metal cations from different sources, such as ground water and mining process waters. Not only was this material highly efficient at collecting several metal ions out of solution it also proved to be regenerable and reusable over a number of adsorption/desorption, which is crucial for environmental friendliness. This material has several advantages compared to the currently used approaches, such as no need for any precipitation step.

Systematic study of the physicochemical properties of a homologous series of aminobisphosphonates

Aminobisphosphonates, e.g., alendronate and neridronate, are a well known class of molecules used as drugs for various bone diseases. Although these molecules have been available for decades, a detailed understanding of their most important physicochemical properties under comparable conditions is lacking. In this study, ten aminobisphosphonates, H2N(CH2)nC(OH)[P(O)(OH)2]2, in which n = 2–5, 7–11 and 15 have been synthesized. Their aqueous solubility as a function of temperature and pH, pKa-values, thermal stability, IR absorptions, and NMR spectral data for both liquid (1H, 13C, 31P-NMR) and solid state (13C, 15N and 31P-CPMAS NMR) were determined.

Structural requirements for bisphosphonate binding on hydroxyapatite: NMR study of bisphosphonate partial esters.

Eighteen different bisphosphonates, including four clinically used bisphosphonate acids and their phosphoesters, were studied to evaluate how the bisphosphonate structure affects binding to bone. Bisphosphonates with weak bone affinity, such as clodronate, could not bind to hydroxyapatite after the addition of one ester group. Medronate retained its ability to bind after the addition of one ester group, and hydroxy-bisphosphonates could bind even after the addition of two ester groups. Thus, several bisphosphonate esters are clearly bone binding compounds. The following conclusions about bisphosphonate binding emerge: (1) a hydroxyl group in the geminal carbon takes part in the binding process and increases the bisphosphonates ability to bind to bone; (2) the bisphosphonates ability to bind decreases when the amount of ester groups increases; and (3) the location of the ester groups affects the bisphosphonates binding ability.

BISPHOSPHONATE PRODRUGS. SYNTHESIS AND IDENTIFICATION OF (1-HYDROXYETHYLIDENE)-1,1-BISPHOSPHONIC ACID TETRAESTERS BY MASS SPECTROMETRY, NMR SPECTROSCOPY AND X-RAY CRYSTALLOGRAPHY

Abstract The preparation and identification of symmetric, H3CC(OH)[P(O)(OR)2]2, where R˭Me, Et, Pri, Ph, and non-symmetric, H3CC(OH)[P(O)(OR)1)(OR2)][P(O)(OR3)(OR4)], where R1˭Me, R2˭R3˭R4˭Ph; R1˭R2˭R3˭Ph, R4˭Me; R1˭R3˭Me, R2˭R4˭Ph; R1˭R2˭Et, Pri, Ph and R3˭R4˭Me; Tetraester derivatives of etidronate have been studied. Compounds were prepared from HP(O)(OR1)(OR2) and AcP(O)(OR3)(OR4) species under reflux. Mechanism studies have been made using HP(O)(OCD3)(OPh) and AcP(O)(OMe)(OPh) as starting materials. 1H, 13C, 31P NMR data and the MS fragmentation data in the gas phase are reported. The solid-state structures are given for three of the compounds, where R˭Et, Ph and R1˭R2˭Ph, R3˭R4˭Me.

A novel bisphosphonate-based solid phase method for effective removal of chromium(III) from aqueous solutions and tannery effluents

Effective removal of chromium(III) from waste waters e.g. in the leather industry is required due to continuously tightening environmental regulations, and several methods such as precipitation and adsorption are currently in use. Nevertheless, more efficient, straightforward and inexpensive methods are constantly being sought. The current study describes a novel method to separate chromium(III) from aqueous solutions based on the use of solid bisphosphonates with a P–C–P backbone. Five classes of bisphosphonates with different functional groups and alkyl chain lengths at the center carbon, in all 16 compounds, were prepared and their suitability for metal ion complexing as chelating agents was investigated. Two of the studied compounds, which were almost insoluble in water, were effective in removing chromium(III) quantitatively from aqueous solutions and real waste water samples of tanneries. The results obtained were also compared to the commercially available Diphonix® resin.

Synthesis of novel (1-alkanoyloxy-4-alkanoylaminobutylidene)-1,1-bisphosphonic acid derivatives

A novel strategy for the synthesis of (1-alkanoyloxy-4-alkanoylaminobutylidene)-1,1-bisphosphonic acid derivatives (1a-d) via (1-hydroxy-4-alkanoylaminobutylidene)-1,1-bisphosphonic acid derivatives (2a-d), starting from alendronate has been developed with reasonable 51–77% overall yields. Intermediate products, (1-hydroxy-4-alkanoylaminobutylidene)-1,1-bisphosphonic acid derivatives (2a-d), were prepared in water with reasonable to high yields (52–94%).

First bisphosphonate hydrogelators: potential composers of biocompatible gels

Recently, investigation of hydrogels has gained ever increasing attention mostly because of their biomedical and pharmaceutical properties, and novel hydrogelators are constantly studied to find functional applications. Bisphosphonates (BPs) are well-known compounds applicable in different fields but are mostly used in clinics as drugs for bone-related diseases. In this study, a novel class of BP-hydrogelators together with a BP-organogelator was found, and the gelating abilities of the compounds were studied. Several techniques to analyze the structure and the properties of the formed gels were used, including solid state 13C and 31P CPMAS and solution state NMR spectroscopy, IR spectroscopy, PXRD, thermoanalysis, as well as SEM.

First synthesis of etidronate partial amides starting from PCl3.

Methods for the preparation of mixed tetra-amide esters 1 and 2, the partial amide ester 3, and tri- and P,P-diamides 4 and 5 from monophosphorus spieces 12, 8 and 9, respectively, were developed. Compounds 8 and 9 were obtained from phosphorus trichloride via MeOPCl2, which was treated with 2 eq. and 4 eq. of piperidine, followed by water or acetyl chloride, respectively. Tetrasubstituted amide bisphosphonates 1 and 2 were selectively dealkylated with lithium or silyl halide to achieve target compounds 3-5. Piperidine was found to be a good desilylation reagent. Quantum mechanical calculations illustrate why derivative 2 was produced in low yield. The usefulness of compounds 1, 3 and 4 as prodrugs of etidronate was determined in aqueous buffer and human serum.

Two strategies for the synthesis of the biologically important ATP analogue ApppI, at a multi-milligram scale.

Summary Two strategies for the synthesis of the ATP (adenosine triphosphate) analogue ApppI [1-adenosin-5’-yl 3-(3-methylbut-3-enyl)triphosphoric acid diester] (1) are described. ApppI is an active metabolite of the mevalonate pathway and thus is of major biological significance. Chemically synthezised ApppI was purified by using triethylammonium bicarbonate as the counter ion in ion-pair chromatography and characterized by 1H, 13C, 31P NMR and MS spectroscopical methods.