THE EFFECT OF CHANGE IN CHEMICAL STRUCTURE OF SOME THYROXINE ANALOGUES ON THE METAMORPHOSIS OF RANA PIPIENS TADPOLES1

Abstract
Forty-three different substances structurally related to thyroxine were assayed for their metamorphosing effect on Rana pipiens tadpoles. Triiodinated compounds with iodines at the 3,3[image],5 positions were found more active than tetraiodinated compounds. The 3,5- and 3,3[image] diiodinated compounds tested also had some activity except for the 3,5 diiodothyroformic acid. None of the monoiodinated compounds assayed showed biological activity. The most active compound studied was 3,3[image],5-triiodothyropropionic acid which was 300 times more potent that l-thyroxine.