L. Wanka, C. Cabrele, M. Vanejews, P. R. Schreiner
FULL PAPER
(Phe)], 2.38–1.41 (m, 14 H, adamantane) ppm. 13C NMR
(100 MHz, CDCl3): δ = 175.8 (C=O), 172.2 (C=O), 154.3 (C=O),
144.01 (Cq), 141.4 (Cq), 135.9 (Cq), 129.4, 128.6, 127.6, 127.2,
obtained after evaporation of the solvents was purified by flash
column chromatography eluting with dichloromethane/methanol
(9:1), Rf(46) = 0.21. 199.5 mg (0.33 mmol, 66%) of tripeptide 46
127.1, 125.0, 120.0, 66.0, 52.8, 52.3, 51.1 (Cq), 47.4, 43.0, 42.6 (Cq), was isolated as a colorless powder, m.p. 71 °C. 1H NMR (400 MHz,
40.7, 38.0, 37.9, 35.2, 29.2 ppm.
CDCl3): δ = 7.39 (br. s, 1 H), 7.33–7.22 (m, 3 H, HAr), 7.09–7.05
(m, 2 H, HAr), 6.85 (s, 1 H), 6.04 [d, J = 7.6 Hz, NH(Phe)], 5.71
[s, 1 H, NH(AGly)], 5.17 [br. s, 1 H, NH(His)], 4.88–4.81 [m, 1 H,
Hα(Phe)], 4.21–4.08 [m, 1 H, Hα(His)], 3.73 (s, 3 H, O-CH3), 3.58
(s, 3 H, N-CH3), 3.20–2.91 [m, 4 H, Hβ(Phe) and Hβ(His)], 2.21–
1.51 (m, 14 H, adamantane), 1.44 [s, 9 H, C(CH3)3] ppm. 13C NMR
(100 MHz, CDCl3): δ = 175.7 (C=O), 172.2 (C=O), 169.5 (C=O),
155.3 (C=OBoc), 138.2, 135.8 (Cq), 129.2, 128.5, 128.2, 127.1, 80.4
(Cq), 52.7, 52.3, 52.2, 42.4, 42.1, 40.24, 40.20, 38.0, 37.9, 37.7, 35.0,
(b) H-AGly-Phe-OMe: 2.049 g (3.54 mmol) Fmoc-AGly-Phe-OMe
was dissolved in 30 mL of dry acetonitrile and cooled to 0 °C with
an ice bath. 30 mL of diethylamine was slowly added and the mix-
ture was stirred for 1 h at 0 °C and 24 h at room temp. The solvents
were evaporated under reduced pressure and the residue was puri-
fied by silica gel column chromatography eluting with tert-butyl
methyl ether/methanol/triethylamine (20:10:1), Rf = 0.30. After
careful evaporation of the eluent, 1.187 g (3.33 mmol, 94.1%) of
the N-deprotected dipeptide was obtained as a slightly yellowish
31.4, 29.0, 28.2, 26.7 ppm. IR (KBr): ν = 3434, 2913, 1740, 1701,
˜
1659, 1509, 1366, 1169 cm–1. MS (ESI): m/z = 608.3 [M + H]+;
(calcd. 608.3). C33H45N5O6 (607.74): calcd. C 65.22, H 7.46, N
11.52; found C 64.78, H 7.49, N 11.44.
1
solid, m.p. 86 °C. H NMR (200 MHz, CDCl3): δ = 7.33–7.15 (m,
3 H), 7.12–6.99 (m, 2 H), 6.12–5.99 (br. d, NH), 4.93–4.78 [m, 1
H, Hα (Phe)], 3.72 (s, 3 H, OCH3), 3.23–3.00 [m, 2 H, Hβ (Phe)],
2.26–2.09 (m, 2 H), 1.79–1.70 (m, 12 H, adamantane) ppm. 13C
NMR (50 MHz, CDCl3): δ = 176.3 (C=O), 172.2 (C=O), 135.9
(Cq), 129.3, 128.5, 127.1, 52.7, 52.3, 47.8 (Cq), 47.6, 45.0, 43.0 (Cq),
N-[3,5-Bis(trifluoromethyl)phenyl]-NЈ-3{[carboxy(glycine methyl es-
ter)amido]tricyclo [3.3.1.13,7]dec-1-yl}thiourea (47a). (a) Fmoc-AGly-
Gly-OMe: In an oven-dried 100 mL flask under argon, 126 mg
(1 mmol) of glycine methyl ester hydrochloride, 418 mg (1 mmol)
of Fmoc-AGly (13a) and 417 mg (1.1 mmol) of HBTU were dis-
solved in 30 mL dry THF. 259 mg (2 mmol) of DIPEA was added
and the mixture was stirred overnight at room temp., then 1 h at
60 °C. After cooling to room temp., 50 mL of brine was added
and the mixture was extracted with CHCl3. The combined organic
phases were washed with 1 HCl, 5% aqueous NaHCO3, water
and brine and dried (Na2SO4). The solvents were evaporated under
reduced pressure and the residue was purified by silica gel column
chromatography eluting with ethyl acetate, Rf = 0.48. After evapo-
ration of the eluent, 431 mg (0.88 mmol, 88.3%) of the dipeptide
was obtained as a colorless powder, m.p. 128 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.75 (d, J = 7.5 Hz, 2 H), 7.58 (d, J =
7.4 Hz, 2 H), 7.38 (t, J = 7.4 Hz, 2 H), 7.32 (t, J = 7.4 Hz, 2 H),
6.15 (br. s, 1 H, NH), 4.72 (br. s, 1 H, NH), 4.44–4.23 (m, 2 H,
Fmoc-CH2), 4.19 (t, J = 6.3 Hz, 1 H), 4.00 [d, J = 5.1 Hz, 2 H, Hα
(Gly)], 3.74 (s, 3 H, OCH3), 2.40–1.31 (m, 14 H, adamantane) ppm.
13C NMR (100 MHz, CDCl3): δ = 176.6 (C=O), 170.6 (C=O),
154.4 (C=O), 144.1 (Cq), 141.4 (Cq), 127.6, 127.1, 124.9, 120.0,
65.9, 52.3, 51.1 (Cq), 47.4, 43.0, 42.6, 41.2, 40.8 (Cq), 38.1, 35.2,
38.0, 37.8, 29.5 ppm. IR (KBr): ν = 3329, 3029, 2906, 2851, 1741,
˜
1642, 1529, 1496, 1454, 1216, 702 cm–1. MS (EI, 70 eV): m/z =
356 (4.8%), 299 (5.0%), 239 (3.3%), 194 (55.6%), 150 (100%), 120
(19.7 %), 94 (33.4 %). HRMS: found 356.2078, calcd. 356.2030.
C
21H28N2O3 (356.46): calcd. C 70.76, H 7.92, N 7.86; found C
70.71, H 7.84, N 7.89.
(c) Boc-His(τ-Bn)-AGly-Phe-OMe (45): 357 mg (1 mmol) H-AGly-
Phe-OMe (1 mmol), 345 mg Boc-His(τ-Bn)-OH (1 mmol), and
379 mg (1 mmol) HBTU were dissolved in 50 mL dry THF. 171 µL
(1 mmol) of DIPEA was added and the mixture was stirred under
argon at room temp. for 15 h. 50 mL of brine and 50 mL of chloro-
form were added, the layers were separated and the aqueous phase
was extracted with chloroform (3ϫ30 mL). The combined organic
phases were washed with 1 HCl, 5% NaHCO3, water and brine
(2ϫ30 mL each) and dried (Na2SO4). The crude product obtained
after evaporation was purified by flash column chromatography
eluting with dichloromethane/methanol (95:5), Rf(45) = 0.40.
603 mg (0.88 mmol, 88%) of tripeptide 50 were obtained as a color-
less powder, m.p. 97 °C. 1H NMR (400 MHz, CDCl3): δ = 7.46–
7.44 (m, 1 H), 7.38–7.22 (m, 6 H), 7.19–7.15 (m, 2 H), 7.11–7.06
(m, 2 H), 6.72 (br. s, 1 H), 6.57 (br. s, 1 H, NH), 6.20 (br. s, 1 H,
NH), 6.04 (d, J = 7.4 Hz, 1 H), 5.04 (s, 2 H, CH2Ph), 4.89–4.82
[m, 1 H, Hα(Phe)], 4.29 [br. s, 1 H, Hα(His)], 3.73 (s, 3 H, OCH3),
3.20–3.05 [M, 3 H, Hβ(Phe) and Hβ (His)], 2.88–2.80 [m, 1 H, Hβ
(His)], 2.22–1.50 (m, 14 H, adamantane), 1.46 [s, 9 H, C(CH3)3]
ppm. 13C NMR (100 MHz, CDCl3): δ = 176.0 (C=O), 172.2
(C=O), 170.8 (C=O), 138.6 (Cq), 136.5, 136.0 (Cq), 135.9 (Cq),
129.3, 129.0, 128.6, 128.3, 127.5, 127.1, 117.3, 79.7 (Cq), 52.8, 52.3,
51.8, 50.9, 42.5, 42.4, 40.3, 40.1, 38.1, 38.0, 37.8, 35.2, 30.7, 29.1,
29.2 ppm. IR (KBr): ν = 3330, 3065, 2947, 2925, 2910, 2857, 1750,
˜
1698, 1637, 1524, 1293, 1272, 1256, 1247, 1222, 1206, 1280, 765,
744 cm–1. MS (ESI): m/z = 511.5 [M + Na]+ (calcd. 511.2).
C29H32N2O5 (488.57): calcd. C 71.29, H 6.60, N 5.73; found C
70.99, H 6.57, N 5.62.
(b) H-AGly-Gly-OMe: 977 mg (2 mmol) of Fmoc-AGly-Gly-OMe
was dissolved in 25 mL of dry acetonitrile and cooled to 0 °C with
an ice bath. After slow addition of 25 mL of diethylamine the mix-
ture was stirred for 1 h at 0 °C and 15 h at room temp. The solvents
were evaporated under reduced pressure and the residue was puri-
fied by silica gel column chromatography eluting with tert-butyl
methyl ether/methanol/triethylamine (20:10:1), Rf = 0.28. After
careful evaporation of the eluent, 520 mg (1.95 mmol, 97.6%) of
the N-deprotected dipeptide was obtained as a slightly yellowish
28.4 ppm. IR (KBr): ν = 3337, 2976, 2911, 2856, 1741, 1701, 1654,
˜
1507, 1455, 1365, 1249, 1169 cm–1. MS (ESI): m/z = 684.3 [M +
H]+; (calcd. 684.4). C39H49N5O6 (683.84): calcd. C 68.50, H 7.22,
N 10.24; found C 68.01, H 7.21, N 10.03.
Boc-His(π-Me)-AGly-Phe-OMe (46): 178.2 mg (0.5 mmol) of H-
AGly-Phe-OMe, 134.7 mg (0.5 mmol) of Boc-His(π-Me)-OH and
189.6 mg (0.5 mmol) HBTU were dissolved in 30 mL dry THF.
86 µL (0.5 mmol) of DIPEA was added and the mixture was stirred
under argon at room temp. for 16 h. 30 mL of brine and 30 mL of
chloroform were added, the layers were separated and the aqueous
layer was extracted with chloroform (3ϫ20 mL). The combined
organic phases were washed with 1 HCl, 5% NaHCO3, water,
and brine (2ϫ20 mL each) and dried (Na2SO4). The crude product
solid, m.p. 104.5 °C. H NMR (400 MHz, CDCl3): δ = 6.18 (br. s,
1
1 H, NH), 4.03 [d, J = 5.1 Hz, 2 H, Hα(Gly)], 3.76 (s, 3 H, OCH3),
2.29–2.13 (m, 2 H), 1.89–1.52 (m, 12 H), 1.71 (s, 2 H, NH2) ppm.
13C NMR (100 MHz, CDCl3): δ = 177.1 (C=O), 170.7 (C=O), 52.4
(OCH3), 47.9 (Cq), 47.7, 45.0, 43.1 (Cq), 41.2, 38.1, 35.2, 29.6 ppm.
IR (KBr): ν = 3353, 2943, 2916, 2852, 1761, 1635, 1525, 1396, 1207,
˜
1183, 1160, 876 cm–1. MS (EI, 70 eV): m/z = 266 (23.4%), 252
(2.6%), 239 (6.7%), 209 (26.3%), 177 (21.3%), 150 (100%), 134
(8.9 %), 120 (76.1 %), 108 (27.8 %), 94 (88.3 %). HRMS: found
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Eur. J. Org. Chem. 2007, 1474–1490