Synthesis and Physicochemical Characterization of the Process-Related Impurities of Olmesartan Medoxomil. Do 5-(Biphenyl-2-yl)-1-triphenylmethyltetrazole Intermediates in Sartan Syntheses Exist?

Complexation of the Antihypertensive Drug Olmesartan with Zn: In Vivo Antihypertensive and Cardiac Effects

This study is based on the premise that the application of chemical synthesis strategies to structurally modify commercial drugs by complexation with biometals is a valid procedure to improve their biological effects. Our purpose is to synthesize a compound with greater efficacy than the original drug, able to enhance its antihypertensive and cardiac pharmacological activity. Herein, the structure of the coordination compound of Zn(II) and the antihypertensive drug olmesartan, [Zn(Olme)(H2O)2] (ZnOlme), is presented. After 8 weeks of treatment in SHR male rats, ZnOlme displayed a better blood pressure-lowering activity compared with olmesartan, with a noticeable effect even in the first weeks of treatment, while ZnCl2 showed similar results than the control. ZnOlme also reduced left ventricle (LV) weight and left ventricle/tibia length ratio (LV/TL), posterior wall thickness (PWT), and intraventricular septum in diastole (IVSd) suggesting its potential to prevent LV hypertrophy. Besides, ZnOlme reduced interstitial fibrosis (contents of collagen types I and III, responsible for giving rigidity and promoting vascular elasticity, respectively). The recovery of heart function was also evidenced by fractional shortening (diastolic left ventricular/systolic left ventricular) diameter determinations. Furthermore, ZnOlme increased the antioxidant capacity and prevented cardiac oxidative stress: it enhanced the reduction of reactive oxygen species generation, exerted a significant decrease in lipid peroxidation and enhanced glutathione contents in heart tissues compared to the control, Zn, and olmesartan treatments. Our results demonstrate that continuous oral administration of ZnOlme causes a better antihypertensive effect and grants enhancement of cardioprotection through antioxidant activity, in combination with hemodynamic improvement.

Crystal structure of 4,5-dimethyl-1,3-dioxol-2-one

4,5-Dimethyl-1,3-dioxol-2-one crystallizes on a mirror plane in P2₁/m and forms layered sheets that comprise anti­parallel linear strands. Close O⋯H, C⋯O and C⋯C inter­molecular contacts are formed between strands and sheets.

The planar title compound 4,5-dimethyl-1,3-dioxol-2-one, C₅H₆O₃, 1, crystallizes with its mol­ecular C₂ axis coincident with a crystallographic mirror plane in space group P2₁/m. In the plane defined by the b axis and an ac face diagonal, anti­parallel linear strands of 1, formed by simple translation, associate to form sheets with close H⋯H and O⋯O inter­molecular contacts. Between the sheets, parallel strands of 1 place the carbonyl O atom near the five-membered ring centroid of a neighboring mol­ecule with close O⋯O and O⋯C contacts.

Permeability of Olmesartan Medoxomil from Lipid Based and Suspension Formulations using an Optimized HDM-PAMPA Model

Hexadecane membrane-parallel artificial membrane permeability assay (HDM-PAMPA) is based on an artificial hexadecane membrane that separates the two compartments (donor and acceptor compartment). This model is used to predict the permeability of drugs in gastrointestinal tract and to simulate the passive absorption. In vivo behaviour of the drugs can be estimated with these systems in drug development studies. In our study we optimized HDM-PAMPA model to determine permeability of olmesartan medoxomil (OM) lipid based drug delivery system (OM-LBDDS). In order to prove that LBDDS formulation facilitates the weak permeability of OM, permeation rates were compared with the OM suspension formula (containing 0.25% v/w CMC). The experiment was performed on a 96-well MultiScreen® PAMPA filter plate (MAIPN4510). The permeability of olmesartan formulations from the donor to acceptor compartment separated by a HDM membrane were determined by the previous validated HPLC method. We created positive control series without coating hexadecane membrane to present the LBDDS and suspension formulation permeability from uncoated plates. The effective permeability constant (P_e) was calculated by the formula and improvement of permeability of OM-LBDDS formulation from hexadecane membrane was confirmed. On the contrary there was no permeation of OM-Suspension in the hexadecane coated plates. As a result, the intestinal permeability of OM-LBDDS was calculated to be at least 100 times more than the suspension. OM-Suspension permeation was only observed in the hexadecane uncoated positive control plates. This was also manifestation of HDM-PAMPA mimicking permeability of intestines because of its lipidic construction.

"Ghost peaks" of olmesartan medoxomil: Two solution degradation products of olmesartan medoxomil via oxidation mediated by metal ions

Two unknown solution degradants were found during the dissolution testing in 0.1-M HCl for olmesartan medoxomil (OLM) tablets. The structure of the degradants was identified and characterized by liquid chromatography-ultraviolet (LC-UV), liquid chromatography with tandem mass spectrometry (LC-MS/MS), and nuclear magnetic resonance (NMR) and demonstrated to be cyclization of tetrazole and benzene in the olmesartan (OL) and OLM structures. A series of studies including stress studies, simulation studies, and mechanism-based studies were performed to reveal the potential mechanisms that lead to the formation of the unknown degradants. The study results demonstrated that the degradation was catalyzed with radicals that originated from the metal ions leached from the inner surface of high-performance liquid chromatography (HPLC) glass vials with dissolved oxygen under acidic condition. Prerinsing the glass vials with acidic solution dissolved with EDTA can effectively avoid the generation of such oxidative impurities. The present work provides new insights into the understanding of degradation pathways of OLM, which might support the development of OLM tablets.

Current Advances in the Synthesis and Biological Evaluation of Pharmacologically Relevant 1,2,4,5-Tetrasubstituted-1H-Imidazole Derivatives

:

In recent years, the synthesis and evaluation of the biological properties of 1,2,4,5-tetrasubstituted-1H-imidazole derivatives have been the subject of a large number of studies by academia and industry. In these studies it has been shown that this large and highly differentiated class of heteroarene derivatives includes high valuable compounds having important biological and pharmacological properties such as antibacterial, antifungal, anthelmintic, anti-inflammatory, anticancer, antiviral, antihypertensive, cholesterol-lowering, antifibrotic, antiuricemic, antidiabetic, antileishmanial and antiulcer activities.

:

The present review with 411 references, in which we focused on the literature data published mainly from 2011 to 2017, aims to update the readers on the recent developments on the synthesis and biological evaluation of pharmacologically relevant 1,2,4,5-tetrasubstituted-1H-imidazole derivatives with an emphasis on their different molecular targets and their potential use as drugs to treat various types of diseases. Reference was also made to substantial literature data acquired before 2011 in this burgeoning research area.

Identification of new process-related impurity in the key intermediate in the synthesis of TCV-116

Development of safe and effective drugs requires complete impurity evaluation and, therefore, knowledge about the formation and elimination of impurities is necessary. During impurity profiling of a key intermediate during synthesis of candesartan cilexetil (1-(((cyclohexyloxy)carbonyl) oxy)ethyl 1-((2'-(2H-tetrazol-5-yl)-[1,1'-biphenyl]-4-yl) methyl)-2-ethoxy-1H-benzo[d]imidazole-7-carboxylate, TCV-116), a novel compound, which had not been reported previously, was observed. Structural elucidation of impurity was achieved by liquid chromatography hyphenated to different high resolution mass analyzers. Based on exact mass measurements and fragmentation pattern, a chloro alkyl carbonate ester analogue of the intermediate was identified. Structure of the impurity was confirmed by mass spectro-metric and NMR analyses of the target substance. Identified impurity could represent a hazard if it is transferred to the final API stage and its presence should be kept below allowed limits. Further investigation could reveal whether bis(1-chloroethyl) carbonate is a precursor to impurity formation. Therefore, synthesis should be regulated so as to minimize impurity production. Analysis of the final product indicated that the amount of impurity did not exceed 50 mg L-1, which represents the detection limit, determined according to the signal/noise ratio.

Development of efficient one-pot three-component assembly of trityl olmesartan medoxomil

We have elaborated a one-pot three-component assembly of trityl olmesartan medoxomil starting from commercially available ethyl 4-(2-hydroxypropan-2-yl)-2-propyl-1H-imidazole-5-carboxylate, 5-(4'-(bromomethyl)-[1,1'-biphenyl]-2-yl)-1-trityl-1H-tetrazole and 4-(chloromethyl)-5-methyl-1,3-dioxol-2-one intermediates. The developed and optimized one-pot process provides 72-75% yield of trityl olmesartan medoxomil over three steps, which represents in average ca. 90% yield per synthetic step, on a 300 g scale. The process is conducted in simple fashion and provides highly pure trityl olmesartan medoxomil (up to 97.5% by HPLC), which can be easily converted to olmesartan medoxomil that fully complies with all ICH requirements. Furthermore, the described process significantly improves the primary process to trityl olmesartan medoxomil by drastic reduction of required unit operations and application of single reaction solvent through the reaction sequence. Moreover, the amount of used organic solvents was notably reduced. The developed process has provided solid bases for industrial production of trityl olmesartan medoxomil.

Fragmentation studies of sartans by electrospray ionization mass spectrometry

Sartans and related analogues with 5-oxo-l, 2, 4-oxadiazole ring and tetrazole ring are investigated in detail using collision-induced dissociation (CID) method in positive ion mode by electrospray ionization tandem mass spectrometry (ESI-MSⁿ ). It is found that the protonated sartans and related analogues tend to form the N-substituted-3-substituted phenanthridin-6-amine ion which has a large conjugative structure. The possible fragmentation pathways were proposed for the first time, and the key structure of product ions was confirmed by high resolution tandem mass spectrometry and theoretical calculation. It is very helpful for understanding the intriguing roles of sartans analogues in fragmentation reactions and enriching the knowledge of the gas-phase chemistry of the oxadiazole and tetrazole ring. Copyright © 2017 John Wiley & Sons, Ltd.

Olmesartan

Olmesartan is an angiotensin receptor blockers with actions similar to those of losartan; it is used for the treatment of high blood pressure by relaxing blood vessels for this reason blood can flow more easily. It could be used alone or in combination with other antihypertensive drugs. This chapter gives a comprehensive profile of olmesartan, containing detailed nomenclature, formulae, elemental analysis, and appearance of the drug. In addition this chapter also describes several methods of synthesis and usage of the olmesartan. The profile covers the physicochemical properties including pK_a value, solubility, X-ray powder diffraction, melting point, and procedures of analysis (compendial, spectroscopic, electrochemical, and chromatographic techniques of analysis). Comprehensive pharmacology is also presented (pharmacological actions, therapeutic uses and dosing, interactions, and adverse effects and precautions). Eighty references were given as a proof of the above-mentioned studies.