New proctolin analogues modified by the novel D-or L-phenylglycine derivatives. Synthesis and biological studies

New analogues of insect neuromodulator proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH), modified in position 2 of the peptide chain by L-or D-phenylglycine and its 4-substituted derivatives were synthesized. For modification of proctolin a series of novel L-or D-phenylglycine derivatives H-Phg(4-NO2)-OH (1), Boc-Phg(4-NO2)-OH (2), Boc-Phg(4-Me2N)-OH (3), H-Phg(4-OBzl)-OH (4), Boc-Phg(4-OBzl)-OH (5), H-D-Phg(4-NO2)-OH (6), Boc-D-Phg(4-NO2,)-OH (7), Boc-D-Phg(4-Me2N)-OH (8), were used. The following proctolin analogues were synthesized: H-Arg-Phg-Leu-Pro-Thr-OH (9), H-Arg-D-Phg-Leu-Pro-Thr-OH (10), H-Arg-Phg(4-OH)-Leu-Pro-Thr-OH (11), H-Arg-D-Phg(4-OH)-Leu-Pro-Thr-OH (12), H-Arg-Phg(4-NO2)-Leu-Pro-Thr-OH (13), H-Arg-D-Phg(4-NO2)-Leu-Pro-Thr-OH (14), H-Arg-Phg(4-NH2)-Leu-Pro-Thr-OH (15), H-Arg-D-Phg(4-NH2)-Leu-Pro-Thr-OH (16), H-Arg-Phg(4-NMe2)-Leu-Pro-Thr-OH (17), H-Arg-D-Phg(4-NMe2)-Leu-Pro-Thr-OH (18). Myotropic activity of proctolin analogues 9-18 was assayed in vitro on the semi-isolated heart of the mealworm Tenebrio molitor and on the foregut of the locust Schistocerca gregaria. All analogues showed a weak or none activity.</p

Myotropic effects of new proctolin analogues modified in the position 5 of peptide chain in insects

To explain the role of the Thr5 residue of proctolin (Arg-Tyr-Leu-Pro-Thr) in the myotropic activity of this insect neuropeptide, we synthesized two groups of its analogues: 1) Arg-Tyr-Leu-Pro-X-OH with X = Val (1), D-Val (2), Ile (3), D-Ile (4), Ala (5), D-Ala (6), Asn (7), Gln (8), Ser (9), Pro (10), Phe (11), Asp (12), Glu (13), Arg (14), D-Arg (15), Lys (16) and Gly (17) and 2) Arg-Tyr-Leu-Pro-R', where R' = isobutylamine (18), S-l-methyl-1-phenylmethylamine (19), R-1-methyl-1-phenylmethylamine (20), R-2-amino-1-propanol (21), S-2-amino-1-propanol (22), R-1-amino-2-propanol (23), S-2-amino-1-propanol (24), 3-amino-1-propanol (25). Decapeptide proctolylproctolin (H-Arg-Tyr-Leu-Pro-Thr-Arg-Tyr-Leu-Pro-Thr-OH) (26) was synthesized. Syntheses of these peptides were carried out by solid-phase method. All peptides were bioassayed in vitro on the semi-isolated hearts of Tenebrio molitor using a cardioexcitatory test and on the foregut of locust (Schistocerca gregaria). Peptides 1, 3, 5, 9, 13, 14, 16, 22, and 23 retained about 30-50% of the cardioexcitatory activity in T. molitor. Analogues 1 and 3 preserved about 50% and analogue 8 about 80% of the myotropic activity, whereas compound 4 and 9 showed a very weak contractile activity in S. gregaria.</p

New proctolin analogues modified by the novel D-or L-phenylglycine derivatives. Synthesis and biological studies

New analogues of insect neuromodulator proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH), modified in position 2 of the peptide chain by L-or D-phenylglycine and its 4-substituted derivatives were synthesized. For modification of proctolin a series of novel L-or D-phenylglycine derivatives H-Phg(4-NO2)-OH (1), Boc-Phg(4-NO2)-OH (2), Boc-Phg(4-Me2N)-OH (3), H-Phg(4-OBzl)-OH (4), Boc-Phg(4-OBzl)-OH (5), H-D-Phg(4-NO2)-OH (6), Boc-D-Phg(4-NO2,)-OH (7), Boc-D-Phg(4-Me2N)-OH (8), were used. The following proctolin analogues were synthesized: H-Arg-Phg-Leu-Pro-Thr-OH (9), H-Arg-D-Phg-Leu-Pro-Thr-OH (10), H-Arg-Phg(4-OH)-Leu-Pro-Thr-OH (11), H-Arg-D-Phg(4-OH)-Leu-Pro-Thr-OH (12), H-Arg-Phg(4-NO2)-Leu-Pro-Thr-OH (13), H-Arg-D-Phg(4-NO2)-Leu-Pro-Thr-OH (14), H-Arg-Phg(4-NH2)-Leu-Pro-Thr-OH (15), H-Arg-D-Phg(4-NH2)-Leu-Pro-Thr-OH (16), H-Arg-Phg(4-NMe2)-Leu-Pro-Thr-OH (17), H-Arg-D-Phg(4-NMe2)-Leu-Pro-Thr-OH (18). Myotropic activity of proctolin analogues 9-18 was assayed in vitro on the semi-isolated heart of the mealworm Tenebrio molitor and on the foregut of the locust Schistocerca gregaria. All analogues showed a weak or none activity.</p

Synthesis and biological evaluation of selected insect neuropeptide analogs modified by D- or L-phenylglycine derivatives

Novel analogs, modified by L- or D- phenylglycine and p-substituted derivatives, of the neuromodulator proctolin (Arg-Tyr-Leu-Pro-Thr) and of the Trypsin Modulating Oostatic Factor from the gray flesh fly Neobellieria bullata (Neb-TMOF-Asn-Pro-Thr-Asn-Leu-His) were synthesized and checked for activity. Proctolin analogs were modified at position 2: Arg-Phg-Leu-Pro-Thr (I), Arg-D-Phg-Leu-Pro-Thr (II), Arg-Phg(p-OH)-Leu-Pro-Thr (III), Arg-D-Phg(p-OH)- Leu-Pro-Thr (IV), Arg-Phg(p-NO2)-Leu-Pro-Thr (V) Arg-D-Phg(p-NO2)-Leu-Pro-Thr (VI), Arg-Phg(p-NH2)-Leu-Pro-Thr (VII), Arg-D-Phg(p-NH2)-Leu-Pro-Thr (VIII), Arg-Phg(p-N,N-di-Me)-Leu-Pro-Thr (IX), Arg-D-Phg (pp-N,N-di-Me)-Leu-Pro-Thr (X) while analogs of Neb-TMOF underwent modifications at position 6: Asn-Pro-Thr-Asn-Leu-Phg(p-NO2) (XI), Asn-Pro-Thr-Asn-Leu-D-Phg(p-NO2) (XII), Asn-Pro-Thr-Asn-Leu-Phg(p-NH2) (XIII), Asn-Pro-Thr-Asn-Leu-D-Phg(p-NH2) (XIV), Asn-Pro-Thr-Asn-Leu-Phg (p-N,N-di-Me) (XV), Asn-Pro-Thr-Asn-Leu-D- Phg(p-N,N-di-Me) (XVI). Earlier studies on proctolin demonstrated that the presence of the -CH2- group between C-α and the phenyl ring at position 2 of the peptide chain is important for the myotropic activity. Based on these results, we replaced Tyr at position 2 by different phenylglycine derivatives, lacking the methylene group at the side chain. Myotropic activity of the proctolin analogs was assayed in vitro on the semi-isolated heart of the mealworm Tenebrio molitor and on the foregut of the locust Schistocerca gregaria. All analogs (I-X) were practically inactive. For Neb-TMOF, it was previously demonstrated that the exchange of His-6 by p-substituted Phe-derivatives, especially by Phe(p-NH2), an amino acid containing a basic function, results into analogs which inhibit trypsin biosynthesis in the gray fleshly. For this reason these new Neb-TMOF analogs with L- or D-phenylglycine p-substituted derivatives at position 6, were developed and tested (in vivo) in the trypsin biosynthesis assay of the gray fleshly N. bullata. Only analogs XV and XVI slightly inhibited trypsin biosynthesis in the midgut. Because more than 50% of the injected animals died and none of the surviving animals ate much of the liver meal, the lower trypsin level in the gut might be a indirect effect. Other peptides (XI-XIV) had no effect on the level of trypsin biosynthesis in the midgut.</p