Preparation of N-(Benzofuranyl-alkoxycarbonyl)-tryptophan ester derivative, used as tachykinin antagonist intermediate, comprises reacting tryptophan ester with carbon dioxide and carbonate, then with benzofuran derivative

摘要

Preparation of (R)-N-(benzo(b)furan-2-ylalkoxycarbonyl)-tryptophan alkyl esters (I) comprises: (i) reacting an (R)-tryptophan alkyl ester (III) with carbon dioxide/alkali metal carbonate mixture as activator; and (ii) reacting the obtained (R)-N-(carboxy)-tryptophan alkyl ester alkali metal salt (IV) with a 2-(substituted alkyl)-benzofuran (V). Preparation of (R)-N-(benzofuranylalkoxycarbonyl)-tryptophan alkyl esters of formula (I) comprises: (i) reacting an (R)-tryptophan alkyl ester of formula (III) with carbon dioxide/alkali metal carbonate mixture in a solvent; and (ii) reacting the obtained (R)-N-(carboxy)-tryptophan alkyl ester salt of formula (IV) with a benzofuran derivative of formula (V). X, Y = 1-10C alkyl; Z' = 1-10C alkylene; and M = alkali metal. N.B. The definitions of X, Y and Z' are taken from the disclosure, since these substituents are undefined in the claims. No general definition of A is given; exemplied A are Cl, Br and tosyloxy.