Process for preparing 14-oxo-(E)-homo-eburnamenine derivatives

摘要

The isomeric mixture of optically active compounds of the formulae <IMAGE> in which R<1> denotes C1-C6-alkyl, is prepared. An optically active tryptophane ester derivative of the formula <IMAGE> in which R<2> = R<1> and A represents an acid radical, is reacted with an alkylvaleroyl halide in the presence of an acid-binding agent to give the optically active halopentanoyl tryptophane ester derivative. This latter is converted by cyclic dehydration and treatment with a base into an optically active hexahydroindoloquinolizinium salt derivative, which is reacted with acrolein to give the hydroxy-dehydro-(E)-homo-eburnameninecarboxylic acid ester derivative. The latter is oxidised to the 14-oxo compound. This compound is selectively reduced, with the isomeric mixture of optically active oxo-(E)-homoeburnamenine- carboxylic acid ester being obtained. This latter is initially treated with an inorganic oxyhalide and then selectively reduced. Using II compounds as the starting material, Ib compounds are obtained after a further process. The conversion of Ia + Ib, as well as of Ib, compounds into Ia compounds is described. The optically active compounds of the Formula Ia are novel. The optically active compounds of the Formula Ib can be used in the preparation of vincamine, which dilates cerebral blood vessels, and of ethyl (+)-apovincaminate.