Analogues of luteinizing hormone‐releasing hormone (LH‐RH) containing dehydroalanine in 6th position

Abstract
(Phe5, ΔAla6)‐LH‐RH and des‐Gly10(Phe5, ΔAla6)‐LH‐RH ethylamide, two analogues of luteinizing hormone‐releasing hormone (LH‐RH), have been synthesised using fragment condensation approach in solution phase with minimum protection of the side chains. The presence of dehydroalanine in peptide fragments was confirmed by1H n.m.r. and chemical analysis. Both the analogues were found to be inactive in comparison to LH‐RH, indicating that α,β‐dehydrogenation of alanine in 6th position is not tolerated and suggesting that flexibility at this position may be crucial for the retention of biological activity.