THE SYNTHESIS OF ZINQUIN ESTER AND ZINQUIN ACID, ZINC(II)-SPECIFIC FLUORESCING AGENTS FOR USE IN THE STUDY OF BIOLOGICAL ZINC(II)

The syntheses of Zinquin ester [ethyl yl-8-(p-tolylsulfonylamino)-6-qu inolyloxy]acetate] and the corresponding acid, both of which are zinc( II)-specific fluorophores, are described. Methoxy-2-methyl-8-(p-tolyls ulfonylamino)quinoline (2) can be demethylated, with boron tribromide, to form either the expected phenol or a mixture of the phenol and the corresponding 5-bromo derivative depending upon the reaction conditio ns. These compounds react with ethyl bromoacetate to give the correspo nding esters, as well as the S-ethoxycarbonyl derivative formed by ele ctrophilic substitution. Halogenation of the sulfonamide (2) occurs re adily at the 5-position. The 5-iodo product undergoes a Heck coupling with ethyl acrylate. The crystal structures of ethyl hyl-8-(p-tolylsul fonylamino)-6-quinolyloxy]acetate and thyl-8-(p-tolylsulfonylamino)-6- quinolyloxy]acetic acid are described.