April 2010
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Table 5. The 1H-NMR Spectrums of the Four Dipeptides Studied
Dipeptide
1H-NMR (500 MHz, CDCl3)
Z-Val-Val-OCH3
Z-Val-Ala-OCH3
Z-Phe-Val-OCH3
Z-Phe-Ala-OCH3
d 0.87—0.96 (m, 9H, 3CH3), 0.99 (d, 3H, CH3), 2.09—2.17 (m, 2H, 2CH), 3.73 (s, 3H, CH3), 4.05 (t, 1H, CH), 4.53 (dd, 1H, CH),
5.11 (s, 2H, CH2), 5.40 (br d, 1H, NH, D2O exchangeable), 6.39 (br d, 1H, NH, D2O exchangeable), 7.30—7.35 (m, 5H, Ar-H).
d 0.92, 0.97 (2d, 6H, 2CH3), 1.40 (d, 3H, CH3), 2.09—2.14 (m, 1H, CH), 3.74 (s, 3H, CH3), 4.01 (t, 1H, CH), 4.57 (t, 1H, CH),
5.10 (s, 2H, CH2), 5.38 (br d, 1H, NH, D2O exchangeable), 6.37 (br d, 1H, NH, D2O exchangeable), 7.30—7.36 (m, 5H, Ar-H).
d 0.80, 0.83 (2d, 6H, 2CH3), 2.07—2.10 (m, 1H, CH), 3.04—3.09 (m, 2H, CH2), 3.68 (s, 3H, CH3), 4.43—4.45 (m, 2H, 2CH),
5.09 (s, 2H, CH2), 5.36 (br d, 1H, NH, D2O exchangeable), 6.27 (br d, 1H, NH, D2O exchangeable), 7.20—7.36 (m, 10H, Ar-H).
d 1.32 (d, 3H, CH3), 3.02—3.14 (m, 2H, CH2), 3.70 (s, 3H, CH3), 4.42—4.51 (m, 2H, 2CH), 5.09 (s, 2H, CH2), 5.32 (br d, 1H, NH,
D2O exchangeable), 6.31 (br d, 1H, NH, D2O exchangeable), 7.26—7.33 (m, 10H, Ar-H).
1
(lit. mp 80—81 °C)14); H-NMR (500 MHz, CDCl3) d: 2.52 (s, 3H, CH3),
7.38—7.44 (m, 3H, Ar-H), 7.57 (t, 1H, Ar-H, Jꢃ7.7 Hz), 7.62 (d, 1H, Ar-H,
Jꢃ8.6 Hz), 7.76 (d, 2H, Ar-H, Jꢃ8.6 Hz), 7.99 (d, 1H, Ar-H, Jꢃ8.6 Hz).
13C-NMR (125 MHz, CDCl3) d: 22.08, 109.61, 120.35, 125.39, 127.14,
128.83, 129.16, 129.37, 129.90, 130.60, 143.01, 148.12. Anal. Calcd for
C13H11N3O3S: C, 53.97; H, 3.83; N, 14.52. Found: C, 54.16; H, 3.98; N,
14.74.
(IR) spectra were recorded on a Perkin-Elmer 1600 series Fourier transform
instrument as KBr pellets. NMR spectra were recorded on a 500 MHz JEOL
and on a 400 MHz Varian mercury spectrometer at room temperature.
Tetramethylsilane (TMS) was used as a reference for all NMR spectra, with
chemical shifts reported as d units (parts per million, ppm) relative to TMS.
Elemental analyses were performed on a Perkin-Elmer 2400 elemental ana-
lyzer, and the values found were within ꢂ0.3% of the theoretical values. The
compounds were illustrated using Chem Draw Ultra version 11, Cambridge
Soft Corporation.
General Method for the Synthesis of Sulfonate Esters (5—12) To a
suspension of 5 mmol of HOBt, HOAt, 1-hydroxypyridin-2(1H)-one, or ethyl
2-cyano-2-(hydroxyimino)acetate in 30 ml of anhydrous CH2Cl2 was added
0.71 ml (5 mmol) of triethylamine with magnetic stirring. The resulting clear
yellow solution was cooled in an ice bath under an atmosphere of N2 and
treated slowly with 1 eq of 4-tosyl chloride or 2-naphthalenesulfonyl chlo-
ride. The reaction mixture was stirred at 0 °C for 30 min and then at room
temperature for 2 h. After dilution with 30 ml of CH2Cl2, the organic phase
was washed with water and saturated aqueous NaCl (30 ml) and dried over
Na2SO4 anhydrous. After removal of the solvent with a rotary evaporator,
the residue was recrystallized from CH2Cl2/hexane to give the sulfonate es-
ters.
3H-[1,2,3]Triazolo[4,5-b]pyridin-3-yl 4-methylbenzenesulfonate (TsOAt,
10): This compound was obtained as colorless crystals, 1.13 g (78%), mp
131—132 °C (lit. mp 133—134 °C)14); H-NMR (500 MHz, CDCl3) d: 2.51
1
(s, 3H, CH3), 7.41—7.45 (m, 3H, Ar-H), 7.87 (d, 2H, Ar-H, Jꢃ7.6 Hz), 8.38
(d, 1H, Ar-H, Jꢃ8.4 Hz), 8.77 (dd, 1H, Ar-H, Jꢃ4.6, 1.6 Hz). 13C-NMR
(125 MHz, CDCl3) d: 22.13, 121.37, 129.53, 129.65, 129.98, 130.85,
134.55, 140.65, 148.05, 152.50. Anal. Calcd for C12H10N4O3S: C, 49.65; H,
3.47; N, 19.30. Found: C, 49.88; H, 3.54; N, 19.12.
2-Oxopyridin-1(2H)-yl 4-methylbenzenesulfonate (TsOPy, 11): This com-
pound was obtained as colorless crystals, 1.08 g (81%), mp 94—95 °C. H-
1
NMR (500 MHz, CDCl3) d: 2.47 (s, 3H, CH3), 6.15 (dt, 1H, Ar-H, Jꢃ6.4,
1.6 Hz), 6.51 (dd, 1H, Ar-H, Jꢃ9.2, 1.6 Hz), 7.29 (m, 1H, Ar-H), 7.37 (d,
2H, Ar-H, Jꢃ8.0 Hz), 7.59 (dd, 1H, Ar-H, Jꢃ7.2, 2.0 Hz), 7.89 (d, 2H, Ar-
H, Jꢃ8.4 Hz). 13C-NMR (125 MHz, CDCl3) d: 22.19, 105.32, 123.41,
130.01, 130.07, 130.09, 130.14, 130.19, 130.67, 137.16, 139.60, 147.44,
157.04. Anal. Calcd for C12H11NO4S: C, 54.33; H, 4.18; N, 5.28. Found: C,
54.15; H, 3.97; N, 5.45.
1H-Benzo[d][1,2,3]triazol-1-yl naphthalene-2-sulfonate (NpsOBt, 5):
This compound was obtained as colorless crystals, 1.33 g (82%), mp 127—
1
128 °C; H-NMR (500 MHz, CDCl3) d: 7.43 (t, 1H, Ar-H, Jꢃ8.4 Hz), 7.57
(t, 1H, Ar-H, Jꢃ7.7 Hz), 7.65 (t, 2H, Ar-H, Jꢃ8.4 Hz), 7.75 (t, 1H, Ar-H,
Jꢃ8.4 Hz), 7.88—8.00 (m, 4H, Ar-H), 8.07 (d, 1H, Ar-H, Jꢃ8.4 Hz), 8.45
(s, 1H, Ar-H). 13C-NMR (125 MHz, CDCl3) d: 109.57, 120.41, 123.16,
125.46, 128.31, 128.41, 128.85, 128.98, 129.45, 129.87, 130.41, 130.81,
131.95, 132.81, 136.46, 143.80. Anal. Calcd for C16H13N3O3S: C, 59.07; H,
3.41; N, 12.92. Found: C, 58.86; H, 3.26; N, 13.09.
Ethyl 2-Cyano-2-(tosyloxyimino)acetate (TsOXY, 12): This compound
was obtained as colorless crystals, 1.27 g (86%), mp 65—66 °C. H-NMR
1
(500 MHz, CDCl3) d: 1.37 (t, 3H, CH3, Jꢃ6.9 Hz), 2.48 (s, 3H, CH3), 4.40
(quart, 2H, CH2, Jꢃ6.9 Hz), 7.40 (d, 2H, Ar-H, Jꢃ7.6 Hz), 7.92 (d, 2H,
Ar-H, Jꢃ7.6 Hz). 13C-NMR (125 MHz, CDCl3) d: 14.00, 22.00, 64.66,
106.20, 129.64, 130.18, 130.36, 131.26, 147.39, 156.02. Anal. Calcd for
C12H12N2O5S: C, 48.64; H, 4.08; N, 9.45. Found: C, 48.89; H, 4.31; N, 9.68.
General Method for the Synthesis of Dipeptides To a solution of
0.1 mmol of Z-Val-OH or Z-Phe-OH and 0.2 mmol of DIEA in 2 ml of DMF
was added 0.1 mmol of the appropriate coupling reagent. The reaction mix-
ture was stirred for preactivation at different times depending on the condi-
tions of the entry studied, followed by the addition of a solution of 0.1 mmol
of Val-OMe·HCl or Ala-OMe·HCl and 0.1 mmol of DIEA in 1 ml of DMF.
The reaction mixture was stirred overnight. After dilution with 50 ml of
ethyl acetate, the organic phase was washed with 5% citric acid (3ꢁ20 ml),
saturated NaHCO3 (3ꢁ20 ml) and saturated NaCl (3ꢁ20 ml) and dried over
Na2SO4 anhydrous. After removal of the solvent with a rotary evaporator,
the residue was recrystallized from CH2Cl2/hexane to give the dipeptide
(Table 5).
3H-[1,2,3]Triazolo[4,5-b]pyridin-3-yl naphthalene-2-sulfonate (NpsOAt,
6): This compound was obtained as colorless crystals, 1.48 g (91%), mp
1
142—143 °C (lit. mp 140—141 °C)14); H-NMR (500 MHz, CDCl3) d: 7.43
(dd, 1H, Ar-H, Jꢃ8.4, 4.6 Hz), 7.67 (t, 1H, Ar-H, Jꢃ8.4 Hz), 7.75 (t, 1H,
Ar-H, Jꢃ8.4 Hz), 7.96—7.99 (m, 3H, Ar-H), 8.08 (d, 1H, Ar-H, Jꢃ8.4 Hz),
8.36 (d, 1H, Ar-H, Jꢃ9.2 Hz), 8.54 (s, 1H, Ar-H), 8.71 (d, 1H, Ar-H, Jꢃ
5.4 Hz). 13C-NMR (125 MHz, CDCl3) d: 121.36, 123.30, 128.28, 128.36,
129.52, 129.57, 129.86, 130.33, 130.75, 131.97, 132.80, 134.53, 136.44,
152.45. Anal. Calcd for C15H10N3O3S: C, 55.21; H, 3.09; N, 17.17. Found:
C, 55.43; H, 2.88; N, 16.92.
2-Oxopyridin-1(2H)-yl naphthalene-2-sulfonate (NpsOPy, 7): This com-
1
pound was obtained as colorless crystals, 1.32 g (88%), mp 93—94 °C; H-
NMR (500 MHz, CDCl3) d: 6.15 (dt, 1H, Ar-H, Jꢃ6.8, 2.0 Hz), 6.48 (dd,
1H, Ar-H, Jꢃ9.2, 2.0 Hz), 7.28 (dt, 1H, Ar-H, Jꢃ6.8, 2 Hz), 7.60—7.66 (m,
2H, Ar-H), 7.72 (dt, 1H, Ar-H, Jꢃ6.8, 1.2 Hz), 7.94—8.05 (m, 4H, Ar-H),
8.57 (s, 1H, Ar-H). 13C-NMR (125 MHz, CDCl3) d: 105.44, 123.45, 123.77,
128.19, 128.42, 128.59, 129.87, 129.92, 130.48, 130.60, 130.63, 131.97,
132.48, 136.39, 137.10, 139.66, 157.08. Anal. Calcd for C15H11NO4S: C,
59.79; H, 3.68; N, 4.65. Found: C, 59.85; H, 3.83; N, 4.54.
Acknowledgments Prof. Ayman El-Faham, University of Alexandria,
College of Science, Chemistry Department, Alexandria, Egypt, and Prof.
Fernando Albericio, University of Barcelona, Spain, are thanked for their
advice and support. The Egyptian Academy of Science is thanked for its
partial support through the Joint Research Project in collaboration with the
Spanish University of Barcelona, Park Scientific (A/9846/07).
Ethyl 2-Cyano-2-(naphthalen-2-ylsulfonyloxyimino)acetate (NpsOXY, 8):
This compound was obtained as colorless crystals, 1.53 g (92%), mp 94—
1
95 °C; H-NMR (500 MHz, CDCl3) d: 1.35 (t, 3H, CH3, Jꢃ7.7 Hz), 4.38
References and Notes
(quart, 2H, CH2, Jꢃ7.7 Hz), 7.69, 7.75 (2t, 2H, Ar-H, Jꢃ7.7 Hz), 7.95—
7.97 (m, 2H, Ar-H), 8.03 (d, 1H, Ar-H, Jꢃ2.3 Hz), 8.05 (d, 1H, Ar-H, Jꢃ
3.8 Hz), 8.68 (s, 1H, Ar-H). 13C-NMR (125 MHz, CDCl3) d: 13.98, 64.69,
106.19, 123.14, 128.22, 128.37, 129.84, 130.00, 130.09, 130.58, 131.46,
131.96, 132.35, 155.94. Anal. Calcd for C15H12N2O5S: C, 54.21; H, 3.64; N,
8.43. Found: C, 54.07; H, 3.79; N, 8.67.
1) Amino acids and peptides are abbreviated and designated following
the rules of the IUPAC-IUB Commission of Biochemical Nomencla-
ture [J. Biol. Chem., 247, 977 (1972)].
2) Albericio F., Carpino L. A., “Methods Enzymol., Solid-Phase Peptide
Synthesis,” Vol. 289, ed. by Fields G. B., Academic Press, Orlando,
FL, 1997, pp. 104—126.
1H-Benzo[d][1,2,3]triazol-1-yl 4-methylbenzenesulfonate (TsOBt,9): This
compound was obtained as colorless crystals, 1.14 g (79%), mp 78—79 °C
3) Albericio F., Kates S. A., “Solid-Phase Synthesis A Practical Guide,”
ed. by Kates S. A., Albericio F., Marcel Dekker, New York, 2000, pp.