Somatostatin Mimic
J ournal of Medicinal Chemistry, 2003, Vol. 46, No. 12 2343
Cyclo[(d ia m in op en t ylca r b a m oyl)H yP r o-P h e-D-Tr p -
Lys-Tyr (Bzl)-P h e] (20): 24 mg from 300 mg of resin, 96%
purity, RtI ) 4.58, RtII ) 11.72, HRMS 1103.5716 (calcd
1103.5718).
carbodiimide; HOBt, hydroxybenzotriazole; DMF, dimeth-
ylformamide; CHO cells, Chinese hamster ovary cells;
COS cells, SV40 transformed African green monkey
kidney cells; GH, growth hormone; IGF-1, insulin-like
growth factor-1; pKi ) -log(Ki); Ki ) IC50/(1 + (L/Kd));
δ pKi ) pKi(analogue) - pKi(SRIF); RtA, retention time
utilizing system A.
Cyclo[(d ia m in oeth ylca r ba m oyl)HyP r o-P h e-D-Tr p -Lys-
Tyr (Bzl)-P h e] (21): 64 mg from 300 mg of resin, 96% purity,
RtI ) 3.16, RtII ) 11.36, HRMS 1061.5247 (calcd 1061.5249).
Cyclo[(d ia m in oeth ylca r ba m oyl)HyP r o-His-D-Tr p -Lys-
Tyr (Bzl)-P h e] (22): 8.5 mg from 300 mg of resin, 100% purity,
RtI ) 10.12, RtII ) 09.56, HRMS 1051.5152 (calcd 1051.5154).
Cyclo[(d ia m in oeth ylca r ba m oyl)HyP r o-Tyr -D-Tr p -Lys-
Tyr (Bzl)-P h e] (23): 7.2 mg from 300 mg of resin, 92% purity,
RtI ) 12.26, RtII ) 10.62, HRMS 1077.5201 (calcd 1077.5198).
Cyclo[(d ia m in oeth ylca r ba m oyl)HyP r o-Ar g-D-Tr p -Lys-
Tyr (Bzl)-P h e] (24): 3.3 mg from 300 mg of resin, 92% purity,
RtI ) 3.78, RtIII ) 9.44, HRMS 1070.5590 (calcd 1070.5576).
Cyclo[(dia m in oeth ylca r ba m oyl)HyP r o-P h g-D-Tr p-Lys-
Tyr (Bzl)-P h e] (25): 3.1 g from 12 g of resin, 98% purity, RtI
) 10.70, RtII ) 10.20, RtIV ) 3.90, HRMS 1047.51 (calcd
1047.5014).
Su p p or tin g In for m a tion Ava ila ble: HRMS, NMR, IR,
and GC spectra. This material is available free of charge via
the Internet at http://pubs.acs.org.
Refer en ces
(1) Brazeau, P.; Vale, W.; Burgus, R.; Ling, N.; Butcher, M.; Rivier,
J .; Guillemin, R. Hypothalamic polypeptide that inhibits the
secretion of immunoreactive pituitary growth hormone. Science
1973, 179, 77-79.
(2) Epelbaum, J . Somatostatin in the central nervous system:
physiology and pathological modifications. Prog. Neurobiol. 1986,
27, 63-100.
(3) Hoyer, D.; Luebbert, H.; Bruns, C. Molecular pharmacology of
somatostatin receptors. Naunyn-Schmiedeberg’s Arch. Pharma-
col. 1994, 350 (5), 441-453.
(4) Bruns, C.; Weckbecker, G.; Raulf, F.; Kaupmann, K.; Schoeffter,
P.; Hoyer, D.; Lubbert, H. Molecular pharmacology of soma-
tostatin-receptor subtypes. Ann. N. Y. Acad. Sci. 1994, 733 138-
46.
(5) Patel, Y. C. Somatostatin and its receptor family. Front. Neu-
roendocrinol. 1999, 20, 157-198.
(6) Hannon, J . P.; Bruns, C.; Weckbecker, G.; Hoyer, D. Somatosta-
tin receptor gene family-subtype selectivity for ligand binding.
In Somatostatin; Patel, Y. C., Ed.; in press.
(7) Reisine, T.; Bell, G. I. Molecular properties of somatostatin
receptors. Neuroscience 1995, 67, 777-790.
(8) Reisine, T.; Bell, G. I. Molecular biology of somatostatin recep-
tors. Endocr. Rev. 1995, 16, 427-442.
Cyclo[(N,N-d im eth yld ia m in oeth ylca r ba m oyl)HyP r o-
P h e-D-Tr p -Lys-Tyr (Bzl)-P h e (26): 53 mg from 300 mg of
resin, 97% purity, RtI ) 14.53, RtII ) 11.51, HRMS 1089.5561
(calcd 1089.5562).
5.1.4. Assign m en t of Am in o Acid Con figu r a tion Usin g
Am in o Acid An a lysis. A sensitive and selective method for
the unambiguous assignment of the absolute configuration of
the amino acids in 25 was utilized. Compound 25 was
hydrolyzed under acidic conditions, and the individual amino
acids were converted to the respective N(O)-trifluoroacetyl
isopropyl esters. The separation of the enantiomers and
assignment of the configuration of each amino acid were
carried out by enantioselective gas chromatography/chemical
ionization mass spectrometry. The expected configurations of
the amino acids were proven.
(9) Bruns, C.; Weckbecker, G.; Raulf, F.; Lu¨bbert, H.; Hoyer, D.
Characterization of somatostatin receptor subtypes. In Soma-
tostatin and Its Receptors, Reichlin, S., Ed.; Ciba Foundation
Symposium 190; Wiley: Chichester, 1995, pp 89-110.
(10) Froidevaux, S.; Eberle, A N. Somatostatin analogs and radio-
peptides in cancer therapy. Biopolymers 2002, 66 (3), 161-183.
(11) Bauer, W.; Briner, U.; Doepfner, W.; Haller, R.; Huguenin, R.;
Marbach, P.; Petcher, T.; Pless, J . SMS 201-995: A very potent
and selective analogue of Somatostatin with prolonged action.
Life Sci. 1980, 31, 1134-1140.
(12) Murphy, W. A.; Lance, V A.; Moreau, S.; Moreau, J .; Coy, D H.
Inhibition of rat prostate tumor growth by an octapeptide analog
of somatostatin. Life Sci. 1987, 40, 2515-2522.
(13) Coy, D. H.; Taylor, J . E. Receptor-specific somatostatin ana-
logues: Correlations with biological activity. Metabolism 1996,
34 (1), 21-23.
5.1.5. NMR Assign m en t a n d An a lysis. NMR spectra were
measured at 300 K (27 °C) on a Bruker DMX 500 spectrometer
using a selective probe for the 1D 13C spectrum and a triple
inverse probe for 1D 1H and 2D spectra. Sample concentration
was 10 mg in 0.5 mL of pyridine-d5. 1H and 13C shifts are
referenced to TMS (0 ppm). The following NMR experiments
were carried out: (A) 1H NMR, (B) 13C NMR, (C) 1H-1H COSY,
(D) 1H-1H ROESY, (E) 1H-1H TOCSY, (F) 1H-13C COSY, and
1
(G) long-range H-13C COSY. The complete assignment of the
NMR spectra is summarized in Table 2.
5.2. P h a r m a cologica l Ch a r a cter iza tion . Ra d ioliga n d
Bin d in g Assa ys. Radioligand binding assays were performed
as described previously.33 Briefly, membranes from CHO and
COS cells expressing the respective human SRIF receptor
(14) Cai, R. Z.; Szoke, B.; Lu, R.; Fu, D.; Redding, T. W.; Schally, A.
V. Synthesis and biological activity of highly potent octapeptide
analogs of somatostatin. Proc. Natl. Acad. Sci. U.S.A. 1986, 83
(6), 1896-1900.
subtype were incubated with the SRIF receptor ligand Tyr11
[
-
125I]-SRIF in the presence or absence of various concentrations
of SRIF receptor ligands. The incubation was stopped after 1
h by rapid filtration through Whatman GF/C filters. Inhibition
curves were analyzed, and IC50 values were calculated.34
(15) Karashima, T.; Cai, R. Z.; Schally, A. V. Effects of highly potent
octapeptide analogs of somatostatin on growth hormone, insulin
and glucagon release. Life Sci. 1987, 41, 1011-1019.
(16) Patel, Y. C.; Wheatley, T. In vivo and in vitro plasma disap-
pearance and metabolism of somatostatin-28 and somatostatin-
14 in the rat. Endocrinology 1983, 112 (1), 220-225.
(17) Lamberts, S. W. J .; Van Der Lely, A. J .; De Herder, W. W.;
Hofland, L. J . Octreotide. N. Engl. J . Med. 1996, 334, 246-254.
(18) Veber, D. F.; Freidinger, R. M.; Perlow, D. S., J r.; Palaveda, W.
J .; Holly, F. W.; Strachan, R. G.; Nutt, R. F.; Arison, B. J .;
Homnick, C.; Randall, W. C.; Glitzer, M. S.; Saperstein, R.;
Hirschmann, R. A potent cyclic hexapeptide analogue of soma-
tostatin. Nature 1981, 292, 55-58.
Ack n ow led gm en t. R. Aichholz, K. Akyel, S. Arnold,
G. Bovermann, E. Francotte, H. U. Gremlich, F. Kessler,
J . M. Meisbuerger, L. Oberer, F. Roll, and C. Simeon
are acknowledged for the syntheses and NMR, MS,
HPLC, IR, UV, and amino acid analyses. Dr. Rudolf
Duthaler, Novartis Leading Scientist, is acknowledged
for excellent advice concerning this manuscript. Profes-
sor S. W. J . Lamberts, Rotterdam, is acknowledged for
clinical perspectives.
(19) Veber, D. F. Design of a highly active cyclic hexapeptide analogue
of somatostatin. In Peptides: Synthesis, Structure and Function.
Proceedings of the Seventh American Peptide Symposium; Rich,
D. H., Gross, V. J ., Eds.; Pierce Chemical Co.: Rockford, IL,
1981; pp 685-694.
Ap p en d ix
(20) Veber, D. F.; Saperstein, R.; Nutt, R. F.; Freidinger, R. M.; Brady,
S. F.; Curley, P.; Perlow, D. S.; Paleveda, W. J .; Colton, C. D.;
Zacchei, A. G. A super active cyclic hexapeptide analog of
somatostatin. Life Sci. 1984, 34 (14), 1371-1378.
(21) Freidinger, R. M.; Perlow, D. S.; Randall, W. C.; Saperstein, R.;
Arison, B. H.; Veber, D. F. Conformational modifications of cyclic
hexapeptide somatostatin analogs. Int. J . Pept. Protein Res.
1984, 23 (2), 142-150.
Abbr evia tion s a n d Syn on ym s. SRIF, somatotropin
release inhibitory factor; SMS 201-995, octreotide or
Sandostatin; BIM 23014, lanreotide, Somatuline; RC160,
vapreotide; MK-678, seglitide; Fmoc, fluorenylmethoxy-
carbonyl; Boc, tert-butyloxycarbonyl; HPLC, high-
performance liquid chromatography; DIPC, diisopropyl-