Abstract
Six analogues of LH-RH, in which the tryptophan residue in position 3 was replaced by nonprotein amino acids, were synthesized and evaluated for their LH-RH activity. The analogues substituted by amino acids having the fused aromatic ring structure in the side-chain retained relatively high biological activity. In particular, the potency of [3- (1-naphthyl)-L-alanine]3-LH-RH was 187.1% of that of synthetic LH-RH. The results demonstrate that the fused aromatic ring structure of the side-chain in position 3 is a favorable factor, and that the indolyl NH group in the Trp residue is not essential.
