GB805296A - Optically active 7-carboethoxy-3-acetylthioheptanoic acids and their salts - Google Patents

Abstract

The invention comprises (+) and (-)-7-carboethoxy-3-acetylthioheptanoic acids, their salts, both separately and as a mixture, with d- and l-ephedrine and the salt of the (+)-enantiomorph with benzhydrylamine; and the processes of producing these compounds by the following methods. 7-Carboethoxy-3-acetylthioheptanoic acid is contacted with l-ephedrine, preferably in equimolecular amounts, in an inert liquid reaction medium such as a lower ether, dioxan, a lower alcohol, benzene, toluene or aqueous mixtures thereof and the (+)- and (-)-l-ephedrine salts of the acid, thus formed, are separated by contacting the mixture with a suitable solvent, preferably ethyl ether, either by adding the mixture to the ether or by conducting the initial reaction in the presence of ether, whence the (-) salt precipitates and the (+) salt remains in solution, separation then being effected by filtration or decantation. The corresponding (+) and (-) salts of 7-carboethoxy-3-acetylthioheptanoic acid with d-ephedrine are similarly prepared except that here it is the (+) salt which precipitates in ethyl ether and the (-) salt which remains in solution. The (+) and (-) l-ephedrine and d-ephedrine salts may be converted to the free acids by treatment with an acid, preferably an excess of a non-oxidizing mineral acid such as hydrochloric acid and conveniently in an aqueous or organic solvent such as a lower alcohol, benzene, chloroform or mixtures thereof with subsequent recovery of the desired (+)- and (-)-7-carboethoxy-3-acetylthioheptanoic acids by conventional methods, whereby the (-) acid is obtained pure, the (+) acid being purified by reacting it with benzhydrylamine to form a salt thereof in a solvent which is preferably isopropyl ether and subsequently liberating the free acid again by acidification of a solution of the salt. Examples are given. Specifications 805,295, 805,297, 805,298, 805,299 and 805,300 are referred to.