Brief Articles
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 17 5385
25.4, 20.0. HRMS (ESI) m/e calcd for C16H24NO3 [M + H]+
278.1756; obsd, 278.1762.
Supporting Information Available: Experimental details and
refs 16-22. This material is available free of charge via the Internet
3-(2,6-Dimethyl-4-carbamoylphenyl)propanoic Acid (12, Dcp).
Compound 11 (400 mg, 1.43 mmol) was dissolved in TFA (5 mL)
at 0 °C, and the solution was warmed to room temperature and
stirred for 1 h. TFA was then removed, and the residue was
triturated with dry ether. Compound 12 was obtained as a white
References
(1) Morgan, B. A.; Smith, C. F. C.; Waterfield, A. A.; Hughes, J.;
Kosterlitz, H. W. Structure-Activity Relationships of Methionine-
Enkephalin. J. Pharm. Pharmacol. 1976, 28, 660-661.
(2) Ling, N.; Guillemin, R. Morphinomimetic Activity of Synthetic
Fragments of â-Lipotropin and Analogs. Proc. Natl. Acad. Sci. U.S.A.
1976, 73, 3308-3310.
1
solid (280 mg, 89%). H NMR (400 MHz, DMSO-d6) δ 7.80 (s,
1H), 7.49 (s, 2H), 7.34 (s, 1H), 2.86-2.82 (t, 2H), 2.34-2.29 (t,
2H), 2.29 (s, 6H). 13C NMR (100.6 MHz, DMSO-d6) δ 174.5, 168.6,
141.5, 136.4, 132.3, 128.8, 127.7, 33.2, 25.3, 20.1, 20.0. HRMS
(ESI) m/e calcd for C12H16NO3 [M + H]+ 222.1130; obsd,
222.1138.
(3) Schiller, P. W.; Berezowska, I.; Nguyen, T. M.-D.; Schmidt, R.;
Lemieux, C.; Chung, N. N.; Falcone-Hindley, M. L.; Yao, W.; Liu,
J.; Iwama, S.; Smith, A. B., III; Hirschmann, R. F. Novel Ligands
Lacking a Positive Charge for the δ- and µ- Opioid Receptors. J.
Med. Chem. 2000, 43, 551-559.
(4) Schiller, P. W.; Lu, Y.; Weltrowska, G.; Berezowska, I.; Wilkes, B.
C.; Nguyen, T. M.-D.; Chung, N. N.; Lemieux, C. A General New
Concept for the Development of Opioid Peptide Derived µ-, δ- and
κ Antagonists. In Peptides: The WaVe of the Future, Proceedings of
the 2nd International Peptide Symposium/17th American Peptide
Symposium; Lebl, M., Houghten, R. A., Eds.; Kluwer Academic
Publishers: Dordrecht, The Netherlands, 2001, pp 676-678.
(5) Lu, Y.; Nguyen, T. M.-D.; Weltrowska, G.; Berezowska, I.; Lemieux,
C.; Chung, N. N.; Schiller, P. W. [2′,6′-Dimethyltyrosine]dynorphin
A(1-11)-NH2 Analogues Lacking an N-terminal Amino Group:
Potent and Selective κ Opioid Antagonists. J. Med. Chem. 2001, 44,
3048-3053.
(6) Lu, Y.; Weltrowska, G.; Lemieux, C.; Chung, N. N.; Schiller, P. W.
Stereospecific Synthesis of (2S)-2-Methyl-3-(2′,6′-dimethyl-4′-hy-
droxyphenyl)-propionic acid (Mdp) and its Incorporation into an
Opioid Peptide. Bioorg. Med. Chem. Lett. 2001, 11, 323-325.
(7) Weltrowska, G.; Lu, Y.; Lemieux, C.; Chung, N. N.; Schiller, P. W.
A Novel Cyclic Enkephalin Analogue with Potent Opioid Antagonist
Activity. Bioorg. Med. Chem. Lett. 2004, 14, 4731-4733.
(8) Weltrowska, G.; Lemieux, C.; Chung, N. N.; Schiller, P. W. Cyclic
Enkephalin Analogs Containing Various para-Substituted Phenyl-
alanine Derivatives in Place of Tyr1 are Potent Opioid Agonists. J.
Peptide Res. 2005, 65, 36-41.
(9) Dolle, R. E.; Machaut, M.; Martinez-Teipel, B.; Belanger, S.; Cassel,
J. A.; Stabley, G. J.; Graczyk, T. M.; DeHaven, R. N. (4-
Carboxamido)phenylalanine is Surrogate for Tyrosine in Opioid
Receptor Peptide Ligands. Bioorg. Med. Chem. Lett. 2004, 14, 3545-
3548.
(10) Schiller, P. W.; Nguyen, T. M.-D.; DiMaio, J.; Lemieux, C.
Comparison of µ-, δ- and κ-Receptor Binding Sites Through
Pharmacologic Evaluation of p-Nitrophenylalanine Analogs of Opioid
Peptides. Life Sci. 1983, 33, 319-322.
(11) Pelton, J. T.; Kazmierski, W.; Gulya, K.; Yamamura, H. I.; Hruby,
V. J. Design and Synthesis of Conformationally Constrained Soma-
tostatin Analogues with High Potency and Specificity for Mu Opioid
Receptors. J. Med. Chem. 1986, 29, 2370-2375.
(12) Portoghese, P. S.; Nagase, H.; Takemori, A. E. Binaltorphimine and
nor-Binaltorphimine, Potent and Selective Kappa-Opioid Receptor
Antagonists. Life Sci. 1987, 40, 1287-1292.
(13) Wentland, M. P.; Lou, R., Ye, Y.; Cohen, D. J.; Richardson, G. P.;
Bidlack, J. M. 8-Carboxamidocylazocine Analogues: Redefining the
Structure-Activity Relationships of 2,6-Methano-3-benzazocines.
Bioorg. Med. Chem. Lett. 2001, 11, 623-626.
Peptide Synthesis. H-c[D-Cys-Gly-Phe(pNO2)-D-Cys]NH2. The
linear precursor peptide of H-c[D-Cys-Gly-Phe(pNO2)-D-Cys]NH2
was prepared by the manual solid-phase technique using Boc-
protection of the R-amino group and Acm protection of the Cys
side chain and DIC/HOBt as coupling agents. The peptide was
assembled on a p-methylbenzhydrylamine resin (1.16 mM/g titrat-
able amine, Bachem Bioscience, King of Prussia, PA) according
to a published protocol.5 The peptide was cleaved from the resin
by HF/anisole treatment in the usual manner. After evaporation of
the HF, the resin was extracted three times with Et2O and
subsequently three times with glacial AcOH. The crude peptide
was obtained in solid form through lyophilization of the acetic acid
extract in 95% yield. Disulfide bond formation was carried out with
the crude peptide using a 10-fold excess of iodine in MeOH/H2O
(4:1) as the oxidation agent. After 30 min at room temperature,
Dowex 2 × 8-400 ion-exchange resin (CH3COO- form) was added,
and the reaction mixture was stirred for an additional 15 min. The
mixture was then filtered, and the colorless filtrate was evaporated
in vacuo to dryness. The residue was dissolved in glacial AcOH,
filtered, and lyophilized. The crude peptide was obtained in solid
form (55% yield) and was purified by preparative HPLC. HPLC
K′ 4.73; TLC Rf 0.15 (I), Rf 0.70 (II); MS [M + H]+ 471.
Dcp-c[D-Cys-Gly-Phe(pNO2)-D-Cys]NH2 (1) and Dhp-c[D-Cys-
Gly-Phe(pNO2)-D-Cys]NH2 (2). To a solution of Dcp or Dhp (0.1
mmol), HBTU (38 mg, 0.1 mmol), and N,N-diisopropylethylamine
(DIEA) (16.5 µL, 0.15 mmol) in 5 mL DMF were added H-c[D-
Cys-Gly-Phe(pNO2)-D-Cys]NH2 × TFA (58.9 mg, 0.1 mmol) and
NMM (11 µL, 0.1 mmol). After stirring for 30 min, the solvent
was evaporated to dryness in vacuo, and the residue was extracted
with 25 mL of AcOEt. After washing with 5% KHSO4, saturated
NaHCO3, and brine, the organic phase was dried (MgSO4), filtered,
and evaporated to dryness in vacuo. The peptide was purified by
reversed-phase HPLC.
Dcp-c[D-Cys-Gly-Phe(pNO2)-D-Cys]NH2 (1). HPLC K′ 2.95:
TLC Rf 0.74 (I), Rf 0.82 (II); MS [M + H]+ 674.
Dhp-c[D-Cys-Gly-Phe(pNO2)-D-Cys]NH2 (2). HPLC K′ 4.54;
TLC Rf 0.81 (I), Rf 0.90 (II); MS [M + H]+ 647.
[Dcp1]Dyn A(1-11)-NH2 (3). The peptide was prepared by the
manual solid-phase technique by using the protocol described above
for the synthesis of the linear precursor peptide of H-[D-Cys-Gly-
Phe(pNO2)-D-Cys]NH2. Side chain protection was as follows: tosyl
(Arg) and 2-chlorobenzyloxycarbonyl (Lys). HPLC K′ 5.77; TLC
Rf 0.21 (I), Rf 0.46 (II); MS [M + H]+ 1402.
(14) Le Bourdonnec, B.; Belanger, S.; Cassel, J. A.; Stabley, G. J.:
DeHaven, R. N.; Dolle, R. E. trans-3,4-Dimethyl-4-(3-carboxami-
dophenyl)piperidines: A Novel Class of µ-Selective Opioid Antago-
nists. Bioorg. Med. Chem. Lett. 2003, 13, 4459-4462.
(15) Zhang, A.; Xiong, W.; Bidlack, J. M.; Hilbert, J. E.; Knapp, B. I.;
Wentland, M. P.; Neumeyer, J. L. 10-Ketomorphinan and 3-Substituted-
3-desoxymorphinan Analogues as Mixed κ and µ Opioid Ligands:
Synthesis and Biological Evaluation of Their Binding Affinity at
Opioid Receptors. J. Med. Chem. 2004, 47, 165-174.
Acknowledgment. This work was financially supported by
the National University of Singapore (to Y.L.) and by operating
grants (to P.W.S.) from the Canadian Institutes of Health
Research (MOP-5655) and the U.S. National Institute on Drug
Abuse (DA-04443).
JM060369K