Journal of Medicinal Chemistry
Article
((((S)-3-bromo-4,5-dihydroisoxazol-5-yl)methyl)carbamoyl)-
pyrrolidine-1-carboxylate (112.8 mg, 0.205 mmol, 62.7% yield over
three steps). An aliquot of the inhibitor was further purified by reverse-
2.53 (m, 1H), 1.94−1.79 (m, 1H). HRMS (ESI-QTOF) m/z:
+
calculated for C26H26BrN4O4 [M + H]+, 537.11319; found,
537.11291.
1
phase HPLC. H NMR (500 MHz, DMSO-d6, mixture of rotational
(2S,4S)-Quinolin-3-ylmethyl 2-((((S)-3-Bromo-4,5-dihydroisoxa-
zol-5-yl)methyl)carbamoyl)-4-(2-hydroxyphenyl)pyrrolidine-1-car-
boxylate, TFA Salt (7c). Compound 7c was prepared analogously to
compound 7e, with the exception that in the amide coupling reaction
within step 4, HBTU (1 equiv) was used as the coupling agent in place
of EDCI HCl with HOBt. The final product was purified by reverse
phase HPLC, furnishing the title compound as its TFA salt (4.9 mg,
0.0073 mmol, 0.92% yield over six steps). 1H NMR (400 MHz,
DMSO-d6, mixture of rotational isomers) δ 9.52 (br s, 1H), 8.97 and
8.89 (2 d, J = 2.1 Hz, 1H), 8.46−8.28 (m, 2H), 8.08−7.97 (m, 2H),
7.81 (ddd, J = 8.5, 6.9, 1.4 Hz, 1H), 7.70−7.61 (m, 1H), 7.09 (dd, J =
7.7, 1.6 Hz, 1H), 7.06−6.98 (m, 1H), 6.79 (ddd, J = 7.2, 5.7, 1.2 Hz,
1H), 6.76−6.65 (m, 1H), 5.38−5.18 (m, 2H), 4.77−4.68 and 4.63−
4.53 (2 m, 1H), 4.42 and 4.32 (2 dd, J = 8.7, 3.1 Hz and 8.8, 2.6, 1H),
3.92 and 3.84 (2 dd, J = 10.0, 7.6 Hz, 1H), 3.66 (dt, J = 15.8, 8.0 Hz,
1H), 3.46−3.29 (m, 2H), 3.30−2.91 (m, 3H), 2.46−2.30 (m, 1H),
2.12−1.97 (m, 1H). HRMS (ESI-QTOF) m/z: calculated for
isomers) δ 9.08 and 8.99 (2 d, J = 2.1 Hz, 1H), 8.62 and 8.55 (2 s,
1H), 8.34 and 8.25 (2 t, J = 6.0 Hz, 1H), 8.15−8.06 (m, 2H), 7.91
(ddd, J = 8.5, 6.9, 1.4 Hz, 1H), 7.79−7.72 (m, 1H), 7.32−7.23 (m,
2H), 7.22−7.14 (m, 3H), 5.38−5.20 (m, 2H), 4.70 and 4.58 (2 ddt, J
= 10.2, 7.2, 4.9, 11.9, 7.1, 4.9 Hz, 1H), 4.36 and 4.25 (2 dd, J = 8.8, 2.5
Hz, 1H), 3.56 and 3.49 (2 dd, J = 10.2, 7.3 Hz, 1H), 3.42−3.05 (m,
4H), 2.94 (ddd, J = 20.3, 17.5, 7.1 Hz, 1H), 2.68−2.57 (m, 2H), 2.55−
2.42 (m, 1H, partly obscured by solvent), 1.94 (ddt, J = 30.7, 12.5, 9.3
Hz, 1H), 1.87−1.76 (m, 1H). 13C NMR (126 MHz, DMSO-d6,
mixture of rotational isomers) δ 172.66 (d, J = 37.4 Hz), 153.67 (d, J =
41.4 Hz), 148.66 (d, J = 61.7 Hz), 143.63 (d, J = 47.2 Hz), 140.21,
138.05, 137.85, 131.45 (d, J = 4.2 Hz), 130.65 (d, J = 5.4 Hz), 128.65
(d, J = 5.6 Hz), 128.52, 128.51−128.35 (m), 128.08 (d, J = 8.7 Hz),
127.59 (d, J = 2.6 Hz), 126.14, 125.94, 80.10 (d, J = 15.5 Hz), 63.52
(d, J = 13.5 Hz), 59.78 (d, J = 74.4 Hz), 51.77 (d, J = 73.8 Hz), 43.34,
41.24 (d, J = 27.6 Hz), 38.45 (d, J = 97.8 Hz), 37.96 (d, J = 16.1 Hz),
36.41 (d, J = 109.2 Hz). HRMS (ESI-QTOF) m/z: calculated for
+
C26H26BrN4O5 [M + H]+, 553.10811; found, 553.10750
+
C27H28BrN4O4 [M + H]+, 551.12884; found, 551.12961.
(2S,4S)-Quinolin-3-ylmethyl 2-((((S)-3-Bromo-4,5-dihydroisoxa-
zol-5-yl)methyl)carbamoyl)-4-(3-hydroxyphenyl)pyrrolidine-1-car-
boxylate, TFA Salt (7d). Compound 7d was prepared using the
procedure of compound 7c and purified by reverse phase HPLC,
furnishing the title compound as its TFA salt (6.7 mg, 0.010 mmol,
1.3% yield over six steps). 1H NMR (400 MHz, DMSO-d6, mixture of
rotational isomers) δ 9.37 (br s, 1H), 8.99 and 8.90 (2 s, 1H), 8.48−
8.29 (m, 2H), 8.10−7.94 (m, 2H), 7.85−7.76 (m, 1H), 7.66 (d, J = 8.9
Hz, 1H), 7.09 (q, J = 7.3 Hz, 1H), 6.75−6.56 (m, 3H), 5.40−5.20 (m,
2H), 4.80−4.57 (m, 1H), 4.49−4.31 (m, 1H), 3.98−3.82 (m, 1H),
3.47−3.15 (m, 4H), 3.15−2.95 (m, 2H), 2.38−2.22 (m, 1H), 2.11 (s,
(2S,4S)-Quinolin-3-ylmethyl 2-((((S)-3-Bromo-4,5-dihydroisoxa-
zol-5-yl)methyl)carbamoyl)-4-phenylpyrrolidine-1-carboxylate (7a,
aka CK805). The title compound was prepared from commercial
(2S,4S)-1-(tert-butoxycarbonyl)-4-phenylpyrrolidine-2-carboxylic by
the general procedure, furnishing (2S,4S)-quinolin-3-ylmethyl 2-
((((S)-3-bromo-4,5-dihydroisoxazol-5-yl)methyl)carbamoyl)-4-phe-
nylpyrrolidine-1-carboxylate (81 mg, 0.151 mmol, 43.9% yield over
three steps) as a white solid. 1H NMR (500 MHz, DMSO-d6, mixture
of rotational isomers) δ 8.93 and 8.86 (2 d, J = 2.2 Hz, 1H), 8.41 and
8.35 (2 t, J = 6.1 Hz, 1H), 8.36 and 8.27 (2 d, J = 1.6 Hz, 1H), 8.03 (d,
J = 8.3 Hz, 1H), 7.99 (dd, J = 17.0, 8.0 Hz, 1H), 7.77 (ddt, J = 8.1, 6.9,
1.1 Hz, 1H), 7.67−7.60 (m, 1H), 7.35−7.27 (m, 4H), 7.26−7.19 (m,
1H), 5.37−5.20 (m, 2H), 4.80−4.71 and 4.66−4.59 (2 m, 1H), 4.46
and 4.37 (2 dd, J = 8.8, 2.2 Hz, 1H), 3.98 and 3.91 (2 dd, J = 9.8, 7.6
Hz, 1H), 3.54−3.18 (m, 5H, partly obscured by residual water), 3.04
(ddd, J = 26.4, 17.6, 7.2 Hz, 1H), 2.43−2.28 (m, 1H), 2.18−2.08 (m,
1H). 13C NMR (126 MHz, DMSO-d6, mixture of rotational isomers) δ
172.52 (d, J = 33.1 Hz), 153.68 (d, J = 41.6 Hz), 150.50 (d, J = 25.3
Hz), 147.12 (d, J = 7.8 Hz), 140.62 (d, J = 22.0 Hz), 138.02 (d, J =
26.7 Hz), 134.42 (d, J = 52.0 Hz), 129.98 (d, J = 4.6 Hz), 129.65 (d, J
= 8.8 Hz), 128.76 (d, J = 3.2 Hz), 128.54 (d, J = 4.4 Hz), 128.09 (d, J
= 15.0 Hz), 127.27 (d, J = 3.9 Hz), 127.15 (d, J = 3.3 Hz), 126.86 (d, J
= 21.8 Hz), 80.11 (d, J = 14.2 Hz), 64.03 (d, J = 15.0 Hz), 59.93 (d, J
= 75.6 Hz), 52.98 (d, J = 61.1 Hz), 43.41, 41.56 (d, J = 59.3 Hz), 40.99
(d, J = 36.4 Hz), 37.82 (d, J = 132.7 Hz). HRMS (ESI-QTOF) m/z:
+
1H). HRMS (ESI-QTOF) m/z: calculated for C26H26BrN4O5 [M +
H]+, 553.10811; found, 553.10725.
(2S,4S)-Quinolin-3-ylmethyl 2-((((S)-3-Bromo-4,5-dihydroisoxa-
zol-5-yl)methyl)carbamoyl)-4-(4-hydroxyphenyl)pyrrolidine-1-car-
boxylate (7e, aka CK937). Step 1: (S)-1-tert-Butyl 2-Methyl 4-(4-
Hydroxyphenyl)-1H-pyrrole-1,2(2H,5H)-dicarboxylate. Adapting a
procedure from the patent literature by Nakai and co-workers,39 (4-
hydroxyphenyl)boronic acid (0.367 g, 2.66 mmol) and tetrakis-
(triphenylphosphine) palladium(0) (0.308 g, 0.266 mmol) were
placed in a 50 mL round-bottom flask and dissolved in 20 mL of
dioxane. Then (S)-1-tert-butyl 2-methyl 4-(((trifluoromethyl)-
sulfonyl)oxy)-1H-pyrrole-1,2(2H,5H)-dicarboxylate (17, 1 g, 2.66
mmol), prepared from (S)-1-tert-butyl 2-methyl 4-oxopyrrolidine-1,2-
dicarboxylate (synthesized from 16 by the method of Qiu40), as
described in the literature reference, was added, followed by potassium
carbonate (4.00 mL, 7.99 mmol) as an aqueous solution. The mixture
was placed in an oil bath that had been preheated to 80 °C and stirred
for 20 min, by which time the solution had turned from orange to dark
black, indicating completion. The solution was concentrated under
reduced pressure and then diluted with water (50 mL). Aqueous HCl
was added to adjust the pH to approximately 5. The mixture was
extracted with ethyl acetate (2 × 50 mL), and the combined organic
extracts were dried and then filtered through a plug of silica. Removal
of the volatiles furnished a gray crude product that was purified by
silica gel chromatography in 10−25% ethyl acetate in pentane to yield
(S)-1-tert-butyl 2-methyl 4-(4-hydroxyphenyl)-1H-pyrrole-1,2-
(2H,5H)-dicarboxylate (18a, where R = p-hydroxyphenyl, 0.484 g,
1.52 mmol, 56.9% yield) (Rf in 15% ethyl acetate in pentane
approximately 0.15). 1H NMR (500 MHz, DMSO-d6, mixture of
rotational isomers) δ 9.72 (s, 1H), 7.32 (dd, J = 8.7, 6.9 Hz, 2H),
6.79−6.72 (m, 2H), 6.08 (m, 1H), 5.02 (dt, J = 5.2, 2.7 Hz, 1H), 4.44
(ddt, J = 9.5, 4.6, 2.1 Hz, 2H), 3.68 and 3.65 (2 s, 3H), 1.44 and 1.36
(2 s, 9H). 13C NMR (126 MHz, DMSO-d6, mixture of rotational
isomers) δ 170.82 (d, J = 49.7 Hz), 158.05, 152.82 (d, J = 72.9 Hz),
139.91 (d, J = 42.3 Hz), 127.38 (d, J = 5.5 Hz), 123.07, 115.52 (d, J =
16.8 Hz), 114.87 (d, J = 12.8 Hz), 79.44 (d, J = 27.2 Hz), 66.75 (d, J =
33.8 Hz), 53.27 (d, J = 7.6 Hz), 52.11 (d, J = 8.2 Hz), 28.01 (d, J =
25.5 Hz).
+
calculated for C26H26BrN4O4 [M + H]+, 537.11319; found,
537.11300.
(2S,4R)-Quinolin-3-ylmethyl 2-((((S)-3-Bromo-4,5-dihydroisoxa-
zol-5-yl)methyl)carbamoyl)-4-phenylpyrrolidine-1-carboxylate
(7b). (S)-1-(tert-butoxycarbonyl)-4-phenyl-2,5-dihydro-1H-pyrrole-2-
carboxylic acid (18b, where R = phenyl) was prepared analogously
as steps 1 and 2 of compound 7e. An aliquot (64 mg, 0.221 mmol) was
dissolved in 10 mL of ethanol (200 proof), and palladium 10% on
carbon (23.5 mg) was added. The round-bottom flask was capped with
a septum and purged with hydrogen gas briefly and kept under a slight
positive pressure of hydrogen while stirring overnight. The reaction
mixture was then filtered through a small layer of silica gel sandwiched
between layers of sand in a pipet column. The matrix was washed with
additional ethanol, and the combined filtrate was evaporated under
reduced pressure, yielding (2S,4R)-1-(tert-butoxycarbonyl)-4-phenyl-
pyrrolidine-2-carboxylic acid (19b, where R = phenyl, 50 mg, 0.172
mmol, 78% yield), which was then elaborated to the final inhibitor
using the general procedure (43.3 mg, 0.081 mmol, 47.1% yield over
1
three steps). H NMR (500 MHz, DMSO-d6, mixture of rotational
isomers) δ 8.97−8.84 (m, 1H), 8.45−8.38 (m, 1H), 8.37 and 8.28 (2 s,
1H), 8.11−7.91 (m, 2H), 7.77 (tt, J = 8.2, 1.3 Hz, 1H), 7.67−7.60 (m,
1H), 7.37−7.21 (m, 5H), 5.38−5.19 (m, 2H), 4.79−4.52 (m, 1H),
4.42−4.23 (m, 1H), 4.13−3.97 (m, 1H), 3.53−2.90 (m, 6H), 2.70−
P
dx.doi.org/10.1021/jm501145a | J. Med. Chem. XXXX, XXX, XXX−XXX