Peptide hormones. 137. Structural requirements in positions 1, 2, 3, and 6 of the luteinizing hormone-releasing hormone (LH-RH) for antiovulatory activity

Abstract
Analogs (16) of the luteinizing hormone-releasing hormone (LH-RH) were synthesized by the solid-phase method. Apparently the substitution of D-Trp [tryptophan] into position 3 of [D- < Glu1 [D-pyroglutamic acid], D-Phe2, amino acid3,D-Phe6]-LH-RH significantly enhanced the antiovulatory potency [rats] but substitution by Pro [proline], N-Me-Phe [N-methyl phenylalanine], N-Me-Leu [N-methyl-leucine], or L-Trp reduced antiovulatory activity. The substitution of L < Glu in L- < Glu in position 1 of [D-Phe2,Pro3,D-Phe6]-LH-RH by cyclohexylcarbonyl (Chc), benzoyl (Bz), Ac [acetyl], Hyp [hydroxyproline], Ac-Met [acetyl-methionine], hydrogen, Pro and D- < Glu residues and the substitution of D-Phe in position 2 by D-Trp, D-His, D-Phg [phenylgycyl] and L-Phe residues caused analog with no antiovulatory activity at 750 .mu.g/rat. Structural requirements for the design of inhibitors of higher potency were discussed.