SYNTHESIS OF C-TERMINAL FRAGMENTS OF BOMBESIN AND THEIR ANALOGUES I. L. Kuranova, S. I. Churkina, V. L. Dyudmirova, E. B. Filonova, F. M. Ibatullin, F. K. Mutulis, I. P. Sekatsis, and V. D. Grigor'eva UDC 547.96.07 With the aim of structural-functional studies in the bombesin series, a number of bombesin fragments and analogues have been synthesized. The synthesis was per- formed by the carbodiimide method and by the activated-ester method. Fragments with the sequences 7-14, 8-14, and 9-14 were obtained by 4 + 4, 3 + 4, and 2 + 4 schemes and a pentapeptide with the sequence 9-13 by a 3 + 2 scheme. Acetylation of the octa- peptide BN(7-14) was carried out by the action of acetic anhydride in pyridine. Analogues of the C-terminal nonapeptide of bombesin [DPhe7]BN(6-14) and [Pro 6, Gly 7, DAIaII]BN(6-14) were synthesized by fragment condensation using the 5 + 4 scheme. The individuality of the compounds obtained was confirmed by their chromatographic behavior on plates coated with silica gel, and by the results of amino acid analysis, high-voltage electrophoresis, and high-performance liquid chromatography, and their structures were confirmed bythe results of high-resolution iH NMR spectros- copy (360 MHz). In experiments on rabbits, in a dose of 1 ~g with central admin- istration the full hypothermic effect of bombesin was shown by the preparation [AcGIn7]BN(7-14), while the preparation [DPhe7]BN(6-14) and [Pro6,GIy7,DAIaII]BN(6-14) possessed only a slight effect (~1% of the activity of bombesin). It has been reported in a number of publications that not only the whole molecule of the tetradecapeptide bombesin from amphibia (BN) but also its C-terminal fragments possess activity. With the aim of a direct search for a reduced structure of amphibian bombesin responsi- ble for the manifestation of biological activity and the subsequent performance of conformation- el-structural analysis in the series of bombesin-like peptides, we have carried out the syn- thesis of a number of C-terminal fragments of bombesin and their analogues by classical methods in solution. 1 2 8 4 5 6 7 8 9 10 II 12 13 14 BN GI9 Gin Arg Leu Oly Asn Gin Trp Ala Val Gly His Leu Met NHz BN (7--143 [AcOinr] BN (7--14) Ac BN (8--14) [Glpr] BN (7--14) Olp ...... BN (9--14) BN (9--13) BN (6--II) [DPher] BN (6--14) --.DPhe,. [Pro6, Glyr, DAlalq BN(6--14) Pro Gly DAIa The synthesis of shortened fragments with the sequence (7-14) (Scheme I), 8-14 (Scheme 2), and 9-14 (Scheme 3) was carried out by the condensation of 4 + 4, 3 + 4, and 2 + 4 fragments, respectively. According to Schemes 1-3, the C-terminal methyl component was valine, and it was therefore possible for racemization to have taken place. In order to show the possibility of using the proposed scheme of synthesis, we subjected a hydrolysate of the nonapeptide BN(6-14) obtained previously by an analogous 5 + 4 scheme [4] to stereo- Leningrad State University. Institute of Organic Synthesis, Latvian SSR Academy of Sciences, Riga. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 554-564, July- August, 1989. Original article submitted June 28, 1988; revision submitted January 6, 1989. 0009-3130/89/2504-0475512.50 © 1990 Plenum Publishing Corporation 475