Conformational analysis of the molecule luteinizing hormone-releasing hormone. 3. Analogue inhibitors and antagonists.

Conformational energy calculations have been carried out on analogues of luteinizing hormone-releasing hormone which have been shown to be potent inhibitors of the release of luteinizing hormone and follicle-stimulating hormone. The analogues included in this study have D-amino acid substitutions in the 2 and/or 3 positions, such as [D-X2]-LH-RH, [D-X2,D-Y3]-LH-RH, [D-X2,Pro3]-lh-rh, and [D-X2,Leu3]-LH-RH. A configurational property which was common to the low-energy conformers of all the analogues is the directional change of the cis-peptide bond of the pyroglutamate ring. Further, there was no overall structural change in the analogues relative to the conformation of native LH-RH, and the orientation of the aromatic side chains relative to one another remained the same throughout this series of analogues.