Preparation and properties of the hydroxyindole-3-carboxylic acids

Abstract

A procedure for the synthesis of the 4-, 5-, 6-, and 7-hydroxyindole-3-carboxylic acids starting from the corresponding 4-, 5-, 6-, and 7-benzyloxyindoles respectively has been devised. The benzyloxyindoles are converted to mixtures of their 1- and 3-carbethoxy derivatives by the action of ethyl chloroformate on their Grignard reagents. The hydroxyindole-3-carboxylic acids are then obtained by the alkaline hydrolysis and debenzylation of the benzyloxy-3-carbethoxyindoles.