Studies On Synthesis And Quality Of Strontium Ranelate

Osteoporosis is a systemic skeletal disorder characterized by low bone mass and microarchitectural deterioration of bone tissue, leading to bone fragility and an increased risk for fractures. The majority of the agents currently available for the treatment of osteoporosis decrease bone resorption (e.g. estrogents, selective estrogents modulators, calcitonin and bisphosphonates), although a few agents have been shown to increase bone formation (e.g. fluoride and parathyroid hormone). Moreover, to date there is no treatment available that can prevent new vertebral or peripheral osteoporosis fractures.Strontium ranelate (distrontium salt of 2-[N,N-di(carboxy- methyl)mino]-3-cyano-4-carboxymethylthiophene-5-carboxylic acid), the novel antiosteoporosis agent was developed by Les Laboratoires Servier. It has a unique mechanism thereby it simultaneously stimulates the formation of new bone tissue and decreases bone resorption, which is for the treatment of postmenopausal osteoporosis to reduce the risk of vertebral and hip fractures.According to the literature, strontium ranelate was synthesized from 5-aminothiophene, and then formed tetraethyl ester of 5-aminothiophene by alkylation, at last strontium ranelate was obtained by hydrolysis and salification in alkaline environment. As 5-aminothiophene isn't commodity, a route of synthesis was designed by using citric acid as raw material, in order to adapt to industrial production and to satisfy production demands of strontium ranelate. As report, tetraethyl ester of 5-aminothiophene was synthesized from 5-aminothio- phene via alkylation, but the yield was low, time consuming was tediously long and purity of target product was poor. Because strontium ranelate is practically insoluble in neutral aqueous media and organic solvents, its recrystallisation was difficult, it's necessary to prepare excellent intermediate for strontium ranelate. In this study, a phase transfer catalysis was used to synthesize tetraethyl ester of 5-aminothiophene with high yield and excellent purity, its data of UV, IR, 1H-NMR, 13C-NMR were in coincidence with report.Strontium ranelate is a new chemical agent, so its pharmaceutical research not been reported. In order to validate strontium ranelate synthesized by new synthesis technique whether could comply with requirement of ICH or not, the quality of strontium ranelate was studied. Not only appearance, solubility and absorption coefficient of strontium ranelate were studied, but also the specific identification was designed and simple, sensitive analytic method for strontium ranelate was established. It was indicated that strontium ranelate which was synthesized by new synthesis technique could comply with requirement of ICH. The research could provide the basis for establishing the quality standard of strontium ranelate. PART 1 Synthesis Technique of Strontium Ranelate(1) Synthesis Technique of Strontium RanelateObjective: To study a new synthesis technique of strontium ranelate, and to adapt to industrial production and achieve demand of drug production.Methods: Strontium ranelate was synthesized from citric acid via decarboxylation, esterification, cyclization, alkylation, hydrolysis and salification and the technique parameter was also optimized.Results: The structure of strontium ranelate that was synthesized by new synthesis technique was identified by UV, IR, 1H-NMR and 13C-NMR. The purity of product was 99.5%, and total yield was 42.6% approximately.Conclusion: The synthesis route was simple, low cost and could be used in industry.(2) Synthesis of Tetraethyl Ester of 5-aminothiophene Objective: To study the synthesis technique of tetraethyl ester of 5-aminothiophene in order to provide intermediate for strontium ranelate.Methods: Tetraethyl ester of 5-aminothiophene was synthesized from 5-aminothiophene by phase transfer catalysis by using ethyl bromocetate as alkylating reagent and potassium carbonate as solid basas. Compared to the yield and purity of tetraethyl ester of 5-aminothiophene, the best condition was discussed.Results: The optimum method was achieved, which was using crown ether as phase transfer catalyst, the molar ratio of alkylating reagent to reactant and alkali to reactant were 2.2 and 2.5 respectively, the reaction temperature was 60℃and the time of the reaction was 6 hours.Conclusion: The method was in advantage of little side reaction, great yield and high purity. The process was suitable for industrial manufacture.PART 2 Quality Study of Strontium Ranelate(1) Characteristics and Identification of Strontium RanelateObjective: To characterize strontium ranelate by studying characteristics, physicochemical constants and identification of strontium ranelate, the research can lay a foundation for quality control and establishment of quality standard on strontium ranelate.Methods: According to Chp (2005), appearance, solubility and the absorption coefficient of strontium ranelate were studied. The method for determining the content of crystal water in strontium ranelate was also designed. The identification of strontium ranelate was carried out by chemical method, UV, IR and HPLC, respectively.Results: Strontium ranelate is powder with off-white color, per molar molecule containing 8 crystal waters was confirmed. It is practically insoluble in neutral aqueous media and organic solvents but can be soluble in the solution of HCl (0.1 mol·L-1) and HAC (0.1 mol·L-1). The absorption coefficient of strontium ranelate in HCl solution at 238 nm and 322 nm were 599.1±4.1 and 641.3±8.5, respectively. The authenticity of strontium ranelate was confirmed from its structure and polar by using chemical method, UV, IR and HPLC, and the identification established was specific.Conclusions: In this work, the characteristics and physico- chemical constants of strontium ranelate were achieved. Specific identification was established, which could confirm the authenticity of strontium ranelate.(2) Test of Strontium RanelateObjective: To study possible impurities in strontium ranelate and establish specific, sensitive method for test of impurities.Methods: According to the appendix of the Chp (2005), the chloride, sulphate, iron and heavy metal in strontium ranelate were analysed. The content of intermediate in strontium ranelate was determined by ultraviolet spectrum, and HPLC method was also adopted to test the related substances in strontium ranelate. Results: the content of mineral impurity in strontium ranelate was not more than 0.015%, and organic impurity was not more than 0.5%.Conclusions: In our work, a simple, rapid and reliable method for test was established to ensure drug safety and utility.(3) Assay of Strontium Ranelate1) Determination of Strontium in Strontium RanelateObjective: To establish an analytic method for strontium in strontium ranelate.Methods:①Complexometric titration: The content of strontium in strontium ranelate was determined through back complexometric titration.②Atomic absorption spectrophotomet- ry: In 0.15% nitric acid, the sample of strontium ranelate was determined by flame atomic spectrophotometry without digesting.Results:①The back complexometric titration for strontium ranelate was accurate and precise. The contents of samples of strontium ranelate were 99.8%, 100.2% and 100.3%, respectively.②The method of atomic absorption spectrophoto- metry for determination of strontium was specific and accurate. A good linear relationship of strontium was obtained at a range of 2~10μg·mL-1. The contents of samples of strontium ranelate were 99.8%, 101.5% and 98.4%, respectively.Conclusion: The compexometric titration for strontium ranelate content was accurate and precise. It was suitable for determination of bulk material. Atomic absorption spectrophoto- metry for the content of strontium ranelate was more specific, and it was not only suitable for bulk material but also for commercial dosages.2) Determination of Ranelic acid in Strontium Ranelate Objective: To study a method of assay for ranelic acid in strontium ranelate, the content of strontium ranelate was calculated on ranelic acid.Methods:①UV: The content of ranelic acid was determined by ultraviolet spectrophotometry at 322 nm.②HPLC: The content of ranelic acid was determined by HPLC The separation was performed on a Hypersil C18 column(150×4.6mm, 5μm) using a mobile phase composed of 20 mmol·L-1solution of EDTA-2Na(containing 0.5% HAc)–methanol(92:8).Results:①The assay for ranelic acid of strontium ranelate was determined by UV method, A good linear relationship of ranelic acid was obtained at a range of 4.02×10-3 ~2.01×10-2 mg·mL-1. The content of samples of strontium ranelate were 99.5%, 101.0% and 100.0%, respectively.②The content of ranelic acid in strontium ranelate was determined by HPLC method. The calibration curves were linear (r=0.999 9) in the range of 5.00×10-3 ~0.320 mg·mL-1 of ranelic acid. LOQ of the method was 1.2μg·mL-1. The contents of samples were 99.1%, 100.9% and 99.2%, respectively.Conclusion: UV for ranelic acid in strontium ranelate was simple, rapid and inexpensive. HPLC for strontium ranelate content was based on the content of ranelic acid in the sample, it was specific and accurate, and was suitable for bulk material and commercial dosages. The methods mentioned above were used to determine two units of the complex. It was indicated that the result was approximately consistent in above methods and the quality of strontium ranelate was well represented.