Pure strontium ranelate preparation in high yield on an industrial scale, useful as anti-osteoporosis agent, by multistage process starting from dialkyl 3-oxoglutarate and malononitrile

摘要

Industrial synthesis of strontium ranelate (I) involves reacting a dialkyl 3-oxoglutarate with malononitrile in methanol in presence of morpholine; reacting with sulfur at reflux; reacting alkyl 5-amino-4-cyano-3-(2-methoxy-2-oxoethyl)-2-thiophene-carboxylate with an alkyl bromoacetate in presence quaternary ammonium compound and potassium carbonate at reflux; and reacting the obtained tetraester with strontium hydroxide. Industrial synthesis of strontium ranelate of formula (I) (or its hydrates) involves: (a) reacting a dialkyl 3-oxoglutarate of formula ROOC-CH2COCH2-COOR (IV) with malononitrile (V) in methanol, in presence of morpholine in an amount of more than 0.95 moles per mole of (IV); (b) reacting the obtained enolate salt of formula (VI) with sulfur in an amount of more than 0.95 moles per mole of (IV), heating the mixture at reflux and isolating the product by precipitation with water followed by filtration; (c) reacting the obtained thiophene derivative of formula (III) with a bromoacetate of formula BrCH2COOR' (VII) in presence of a catalytic amount of at least one 8-10C quaternary ammonium compound of formula R1R2R3R4N+.X- (A) and potassium carbonate at reflux in an organic solvent, followed by filtering, concentrating by distillation, adding a cosolvent, cooling, filtering again and drying the obtained powder; and (d) reacting the obtained tetraester of formula (II) with strontium hydroxide in an amount of at least 2 moles per mole of (II) under reflux in water, followed by filtering the hot mixture, washing the precipitate with boiling water and drying the obtained powder to give (I). R, R', R1 = 1-6C alkyl; R2 - R4 = 8-10C alkyl; X = halogen. Independent claims are included for: (1) Preparation of (III) from (IV) via (VI) as described above; and (2) Preparation of (I) from (II) as described above.