Motilin Antagonists
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 3 673
amorphous solid. H-Phe-c[-Nꢀ-Lys-Tyr(O-secBu)-âAla-] (2) (21.7
mg, yield 4%). 1H NMR (DMSO-d6): δ 0.81 (3H, m, CH3), 1.07
(3H, t, J ) 5.6 Hz, CH3), 1.12-1.36 (4H, m, 2 × CH2), 1.37-
1.67 (4H, m, 2 × CH2), 2.23 (2H, m, CH2), 2.66-2.95 (4H, m,
2 × CH2), 3.20-3.55 (4H, m, 2 × CH2), 3.96 (1H, m, CH), 4.14
(1H, m, CH), 4.30 (1H, m, CH), 4.46 (1H, m, CH), 6.74 (2H, d,
J ) 8.3 Hz, aromatic-H), 7.06 (2H, d, J ) 8.3 Hz, aromatic-
H), 7.16-7.26 (5H, m, aromatic-H), 7.40 (1H, brt, J ) 5.4 Hz,
NH), 7.67 (1H, m, NH), 8.49 (1H, d, J ) 9.2 Hz, NH), 8.61
(1H, d, J ) 17.5 Hz, NH). FAB-MS m/z: calcd 566.3342, found
566.3352 (MH)+.
H-P h e-c[-NE-Lys-Tyr (3-tBu )-âAla -] (3) a n d H-P h e-c[-NE-
Lys-Tyr (3,5-d i-tBu )-âAla -] (5). H-Phe-c[-Nꢀ-Lys-Tyr-âAla-]
(1) (170 mg) was dissolved in TFA (10 mL), and TMSOTf (0.1
mL) was added. Isobutene gas was added for 20 min at -10
°C, and the mixture was left for 12 h at room temperature.
The reaction solution was added dropwise to excess cold diethyl
ether, and the precipitated peptide was collected by centrifu-
gation and dried. The crude peptide was purified by prepara-
tive HPLC with a linear gradient of 0-60% of 0.1% TFA in
acetonitrile against 0.1% aqueous TFA over 60 min at 10 mL/
min. The lyophilized products were white amorphous solids.
H-Phe-c[-Nꢀ-Lys-Tyr(3-tBu)-âAla-] (3) (85.5 mg, yield 46%). 1H
NMR (DMSO-d6): δ 1.14 (2H, m, CH2), 1.29 (9H, s, 3 × CH3),
1.30, 1.40 (2H, 2m, CH2), 1.54 (2H, m, CH2), 2.19 (2H, m, CH2),
2.67 (1H, dd, J ) 7.9, 13.9 Hz, CH2), 2.84 (2H, m, CH2), 2.94
(1H, dd, J ) 5.5, 14.0 Hz, CH2), 3.26-3.44 (4H, m, 2 × CH2),
4.00 (1H, brt, J ) 5.6 Hz, CH), 4.29 (1H, dt, J ) 5.0, 7.6 Hz,
CH), 4.42 (1H, dt, J ) 7.1, 7.6 Hz, CH), 6.63 (1H, d, J ) 7.9
Hz, aromatic-H), 6.78 (1H, dd, J ) 2.0, 8.0 Hz, aromatic-H),
6.94 (1H, d, J ) 2.0 Hz, aromatic-H), 7.16 (2H, m, aromatic-
H), 7.23 (3H, m, aromatic-H), 7.38 (1H, t, J ) 6.0 Hz, NH),
7.63 (1H, dd, J ) 4.5, 7.5 Hz, NH), 8.38 (1H, d, J ) 8.9 Hz,
NH), 8.57 (1H, d, J ) 7.6 Hz, NH). FAB-MS m/z: calcd
566.3342, found 566.3328 (MH)+.
J ) 6.9, 6.9 Hz, CH), 4.63 (1H, dd, J ) 6.6, 14.5 Hz, CH), 6.89
(2H, d, J ) 8.3 Hz aromatic-H), 7.17 (2H, d, J ) 8.3 Hz,
aromatic-H), 7.20-7.31 (5H, m, aromatic-H). FAB-MS m/z:
calcd 566.3342, found 566.3343 (MH)+
.
H-P h e-c[-NE-Lys-Tyr (3-t Bu )-Gly-] (6). H-Phe-c[-Nꢀ-Lys-
Tyr-Gly-] was synthesized by the same procedure as that for
1 but using NR-Fmoc-Gly-OH, NR-Fmoc-Tyr(tBu)-OPfp, NR-
Fmoc-Lys(Boc)-OPfp, and NR-Fmoc-Phe-OPfp. H-Phe-c[-Nꢀ-
Lys-Tyr(3-tBu)-Gly-] was synthesized by the same procedure
as that for 3 from H-Phe-c[-Nꢀ-Lys-Tyr-Gly-] (878 mg). H-Phe-
c[-Nꢀ-Lys-Tyr(3-tBu)-Gly-] (6) (288 mg, yield 29%). 1H NMR
(DMSO-d6): δ 0.99-1.65 (6H, m, 3 × CH2), 1.32 (9H, s, 3 ×
CH3), 2.67-2.98 (6H, m, 3 × CH2), 3.18-3.34 (2H, m, CH2),
3.82 (1H, dd, J ) 6.1, 15.4 Hz, CH), 4.43 (2H, m, 2 × CH),
6.67 (1H, d, J ) 8.3 Hz, aromatic-H), 6.86 (1H, d, J ) 7.6 Hz,
aromatic-H), 7.02 (1H, s, aromatic-H), 7.20 (5H, s, aromatic-
H), 8.27 (1H, m, NH), 8.55 (1H, d, J ) 7.3 Hz, NH), 8.67 (1H,
m, NH), 8.90 (1H, d, J ) 7.9 Hz, NH). FAB-MS m/z: calcd
552.3186, found 552.3180 (MH)+.
H-P h e-c[-NE-Lys-Tyr (3-tBu )-Abu -] (7). H-Phe-c[-Nꢀ-Lys-
Tyr-Abu-] was synthesized by the same procedure as that for
1 but using NR-Fmoc-Abu-OH, NR-Fmoc-Tyr(tBu)-OPfp, NR-
Fmoc-Lys(Boc)-OPfp, and NR-Fmoc-Phe-OPfp. H-Phe-c[-Nꢀ-
Lys-Tyr(3-tBu)-Abu-] was synthesized by the same procedure
as that for 3 from H-Phe-c[-Nꢀ-Lys-Tyr-Abu-] (747 mg). H-Phe-
1
c[-Nꢀ-Lys-Tyr(3-tBu)-Abu-] (7) (300 mg, yield 25%). H NMR
(DMSO-d6): δ 1.07 (2H, m, CH2), 1.24-1.38 (2H, m, CH2), 1.31
(9H, s, 3 × CH3), 1.54 (2H, m, CH2), 1.87 (2H, m, CH2), 2.22
(2H, m, CH2), 2.64-2.94 (6H, m, 3 × CH2), 3.31 (2H, m, CH2),
4.07 (1H, m, CH), 4.29 (1H, brd, J ) 5.6 Hz, CH), 4.43 (1H, m,
CH), 6.66 (1H, d, J ) 6.6 Hz, aromatic-H), 6.86 (1H, brd, J )
6.3 Hz, aromatic-H), 7.03 (1H, s, aromatic-H), 7.19 (5H, s,
aromatic-H), 7.58 (2H, m, 2 × NH), 8.45 (2H, m, 2 × NH).
FAB-MS m/z: calcd 580.3499, found 580.3495 (MH)+.
H-P h e-c[-NE-Lys-Tyr (3-tBu )-Ah x-] (8). H-Phe-c[-Nꢀ-Lys-
Tyr-Ahx-] was synthesized by the same procedure as that for
1 but using NR-Fmoc-Ahx-OH, NR-Fmoc-Tyr(tBu)-OPfp, NR-
Fmoc-Lys(Boc)-OPfp, and NR-Fmoc-Phe-OPfp. H-Phe-c[-Nꢀ-
Lys-Tyr(3-tBu)-Ahx-] was synthesized by the same procedure
as that for 3 from H-Phe-c[-Nꢀ-Lys-Tyr-Ahx-] (712 mg). H-Phe-
c[-Nꢀ-Lys-Tyr(3-tBu)-Ahx-] (8) (428 mg, yield 34%). 1H NMR
(DMSO-d6): δ 1.02-1.69 (12H, m, 6 × CH2), 1.30 (9H, s, 3 ×
CH3), 2.00 (2H, m, CH2), 2.60-3.23 (8H, m, 4 × CH2), 4.09
(1H, m, CH), 4.39 (2H, m, 2 × CH), 6.64 (1H, d, J ) 8.3 Hz,
aromatic-H), 6.82 (1H, d, J ) 7.9 Hz, aromatic-H), 6.97 (1H,
brs, aromatic-H), 7.20 (5H, brs, aromatic-H), 7.54 (1H, m, NH),
7.72 (1H, m, NH), 8.28 (1H, m, NH), 8.50 (1H, brd, J ) 6.9
Hz, NH). FAB-MS m/z: calcd 608.3812, found 608.3806 (MH)+.
H-Phe-c[-Nꢀ-Lys-Tyr(3,5-di-tBu)-âAla-] (5) (41 mg, yield
20%). 1H NMR (DMSO-d6): δ 1.10-1.67 (6H, m, 3 × CH2),
1.34 (18H, s, 6 × CH3), 2.24 (2H, m, CH2), 2.42-2.58 (2H, m,
CH2), 2.63-3.02 (6H, m, 3 × CH2), 4.03 (1H, m, CH), 4.34 (1H,
m, CH), 4.43 (1H, m, CH), 6.92 (2H, s, aromatic-H), 7.20 (5H,
m, aromatic-H), 7.43 (1H, m, NH), 7.61 (1H, m, NH), 8.65 (1H,
d, J ) 9.1 Hz, NH), 8.58 (1H, d, J ) 8.0 Hz, NH). FAB-MS
m/z: calcd 622.3968, found 622.3961 (MH)+.
H-P h e-c[-NE-Lys-Tyr (O-tBu )-âAla -] (4). Z-Lys-Tyr(tBu)-
âAla-HMPA resin was synthesized by the same procedure as
that for 1 but using NR-Fmoc-âAla-OH, NR-Fmoc-Tyr(O-tBu)-
OH, and Z-Lys(Fmoc)-OH. The peptide resin was treated with
MeOH (270 mL) and triethylamine (30 mL) for 18 h at room
temperature. After filtration, the solution was evaporated to
dryness and treated with MeOH/H2O/Et3N (2:2:1; v/v) for 24
h at room temperature. After evaporation, the residue was
dissolved in DMF (200 mL) and pyridine (200 mL). BOP
reagent (2 g) was added to the solution, and the mixture was
left for 18 h at room temperature. After evaporation, water
was added and the precipitate was filtered, washed once with
5% NaHCO3 (aq) and twice with water. The dried solid was
dissolved in DMF (20 mL) and hydrogenated with Pd/C (200
mg) for 3 h. The solution was filtered and evaporated to
dryness. The residue was dissolved in DMF (5 mL) and coupled
with NR-Fmoc-Phe-OPfp (1.11 g) using HOBt (306 mg) for 18
h at room temperature. After evaporation, water was added
and the precipitate was filtered, washed once with water, and
washed twice with dry ether. The dried solid was dissolved in
DMF (8 mL), treated with piperidine (2 mL) for 1 h, and
evaporated to dryness. The crude peptide was purified by
preparative HPLC with a linear gradient of 0-60% of 0.1%
TFA in acetonitrile against 0.1% aqueous TFA over 60 min at
10 mL/min. The lyophilized product was a white amorphous
solid. H-Phe-c[-Nꢀ-Lys-Tyr(O-tBu)-âAla-] (4) (43 mg). 1H NMR
(CD3OD): δ 1.15-1.28 (2H, m, CH2), 1.25 (9H, s, 3 × CH3),
1.40, 1.53 (2H, 2m, CH2), 1.68 (2H, m, CH2), 2.37 (2H, m, CH2),
2.84 (2H, m, CH2), 3.06 (4H, m, 2 × CH2), 3.41-3.72 (2H, m,
CH2), 3.97 (1H, dd, J ) 5.6, 8.6 Hz, CH), 4.34 (1H, dd,
H-D-P h e-c[-NE-Lys-Tyr (3-tBu )-âAla -] (9). H-D-Phe-c[-Nꢀ-
Lys-Tyr-âAla-] was synthesized by the same procedure as that
for 1 but using NR-Fmoc-âAla-OH, NR-Fmoc-Tyr(tBu)-OPfp,
NR-Fmoc-Lys(Boc)-OPfp, and NR-Fmoc-D-Phe-OPfp (697 mg,
yield 74%). H-D-Phe-c[-Nꢀ-Lys-Tyr(3-tBu)-âAla-] was synthe-
sized by the same procedure as that for 3 from H-D-Phe-c[-
Nꢀ-Lys-Tyr-âAla-] (878 mg). H-D-Phe-c[-Nꢀ-Lys-Tyr(3-tBu)-
1
âAla-] (9) (111 mg, yield 34%). H NMR (DMSO-d6): δ 0.74-
1.07 (2H, m, CH2), 1.12-1.40 (4H, m, 2 × CH2), 1.31 (9H, s,
3 × CH3), 2.20 (2H, m, CH2), 2.60-2.85 (4H, m, 2 × CH2), 2.95
(2H, d, J ) 6.9 Hz, CH2), 3.26-3.44 (2H, m, CH2), 4.15 (1H,
m, CH), 4.27 (1H, m, CH), 4.38 (1H, m, CH), 6.63 (1H, d, J )
7.9 Hz, aromatic-H), 6.76 (1H, brd, J ) 7.6 Hz, aromatic-H),
6.92 (1H, brs, aromatic-H), 7.20-7.40 (6H, m, NH + aromatic-
H), 7.57 (1H, m, NH), 8.38 (2H, d, J ) 8.3 Hz, 2 × NH). FAB-
MS m/z: calcd 566.3342, found 566.3341 (MH)+.
H-P h e-c[-NE-D-Lys-Tyr (3-t Bu )-âAla -] (10). H-Phe-c[-Nꢀ-
D-Lys-Tyr-âAla-] was synthesized by the same procedure as
that for 1 but using NR-Fmoc-âAla-OH, NR-Fmoc-Tyr(tBu)-
OPfp, NR-Fmoc-D-Lys(Boc)-OPfp, and NR-Fmoc-Phe-OPfp (796
mg, yield 85%). H-Phe-c[-Nꢀ-D-Lys-Tyr(3-tBu)-âAla-] was syn-
thesized by the same procedure as that for 3 from H-Phe-c[-
Nꢀ-D-Lys-Tyr-âAla-]. H-Phe-c[-Nꢀ-D-Lys-Tyr(3-tBu)-âAla-] (10)
(100 mg, yield 31%). 1H NMR (DMSO-d6): δ 0.92 (2H, m, CH2),
1.10-1.53 (4H, m, 2 × CH2), 1.30 (9H, s, 3 × CH3), 2.16 (2H,