T. Yamakawa et al. / Tetrahedron 67 (2011) 6547e6560
6557
concentrated in vacuo. The residue was purified with flash column
chromatography on silica gel (hexane/EtOAc¼7/3) to afford 65
room temperature. After 30 min, the reaction mixture was
quenched with saturated aq NH4Cl and the aqueous phase was
extracted with EtOAc three times. The combined organic layer was
washed with brine, dried over Na2SO4, filtered, and concentrated in
vacuo. The residue was purified with flash column chromatography
(1.10 g, 2.40 mmol, 88%) as a colorless oil. Boc intermediate: mp
23
110e111 ꢀC; [
a
]
ꢁ33 (c 1.00, CHCl3); IR (neat, cmꢁ1) 2979, 2933,
D
2874,1809, 1732, 1697, 1607, 1459, 1390,1366,1327; 1H NMR (CDCl3,
400 MHz) (1:1 mixture of two rotamers) (major)
d
8.08e8.06 (m,
on silica gel (hexane/EtOAc¼4/1) to afford 68 (1.10 g, 1.88 mmol,
21
1H), 7.61 (d, J¼7.3 Hz, 1H), 7.27e7.16 (m, 2H), 5.18 (t, J¼5.0 Hz, 1H),
4.22e4.14 (m, 1H), 3.90e3.72 (m, 2H), 3.69 (s, 2H), 3.23 (dd, J¼11.5,
1.0 Hz, 1H), 2.82e2.74 (m, 1H), 1.77 (s, 3H), 1.73 (s, 3H), 1.66 (s, 9H),
88%) as a colorless oil. [
a
]
þ3.3 (c 1.00, CHCl3); IR (neat, cmꢁ1
)
D
3307, 2977, 2930, 1733, 1647, 1457, 1365, 1326; 1H NMR (CDCl3,
400 MHz) (3:2 mixture of two rotamers) (major)
d
8.08 (d, J¼5.9 Hz,
1.57 (s, 9H), 1.55 (s, 3H), 1.53 (s, 3H) (minor)
d
8.08e8.06 (m, 1H),
1H), 7.56 (d, J¼7.4 Hz, 1H), 7.26e7.20 (m, 2H), 5.22 (br s, 1H), 5.14 (d,
J¼8.2 Hz, 1H), 4.78e4.72 (m, 1H), 4.55e4.52 (m, 1H), 3.74 (br s, 2H),
3.68 (s, 3H), 3.74e3.65 (m, 1H), 3.47e3.43 (m, 1H), 3.17e3.02 (m,
2H), 2.20e1.95 (m, 4H), 1.77 (s, 3H), 1.70 (s, 3H), 1.66 (s, 9H), 1.30 (s,
7.79e7.77 (m, 1H), 7.27e7.16 (m, 2H), 5.18 (t, J¼5.0 Hz, 1H),
4.22e4.14 (m, 1H), 3.90e3.72 (m, 2H), 3.69 (s, 2H), 3.12 (dd, J¼11.5,
1.4 Hz, 1H), 2.82e2.74 (m, 1H), 1.77 (s, 3H), 1.73 (s, 3H), 1.66 (s, 9H),
1.57 (s, 9H), 1.55 (s, 3H), 1.53 (s, 3H); 13C NMR (CDCl3, 100 MHz)
9H) (minor)
d
8.05 (m, 1H), 7.51 (d, J¼7.4 Hz, 1H), 7.26e7.20 (m, 2H),
(major)
118.2, 115.3, 114.7, 94.2, 83.7, 66.0, 80.0, 56.8, 28.7, 28.1, 27.4, 27.0,
25.8, 25.7, 23.2, 18.2 (minor) 151.4, 150.4, 137.6, 135.8, 132.2, 129.9,
d
151.8, 150.3, 137.8, 135.9, 132.4, 129.7, 123.6, 122.2, 121.6,
5.51 (d, J¼8.7 Hz, 1H), 5.16 (br s, 1H), 4.50e4.44 (m, 1H), 4.55e4.52
(m,1H), 3.74 (br s, 2H), 3.65 (s, 3H), 3.52 (d, J¼8.2 Hz,1H), 3.47e3.43
(m, 1H), 2.98e2.92 (m, 2H), 2.20e1.95 (m, 4H), 1.77 (s, 3H), 1.70 (s,
3H), 1.66 (s, 9H), 1.44 (s, 9H); 13C NMR (CDCl3, 100 MHz) (major)
d
123.5, 122.7, 121.8, 118.9, 115.1, 115.0, 93.4, 83.5, 66.0, 80.1, 57.6, 28.5,
28.0, 27.8, 27.2, 25.9, 25.7, 24.4, 18.0; HRMS (ESI) calcd for
d
172.3, 171.0, 155.1, 150.3, 138.1, 135.9, 132.1, 129.6, 123.4, 122.5,
122.1, 117.9, 115.3, 113.0, 83.5, 79.4, 58.7, 52.6, 52.1, 46.9, 29.6, 28.3,
27.5, 28.0, 25.7, 24.8, 22.0, 18.2 (minor) 171.7, 171.0, 154.5, 150.3,
C29H42N2NaO5 ([MþNa]þ) 521.2991, found 521.2981. Compound
24
65: [a
]
ꢁ3.1 (c 1.00, CHCl3); IR (neat, cmꢁ1) 3473, 2978, 2930,
d
D
1731, 1696, 1503, 1458, 1392, 1367, 1327; 1H NMR (CDCl3, 400 MHz)
138.4, 135.6, 132.6, 129.4, 123.8, 122.6, 121.2, 118.2, 115.0, 113.1, 83.9,
79.3, 58.7, 52.2, 51.5, 46.1, 30.0, 28.9, 27.6, 27.5, 25.8, 24.8, 22.0, 18.1;
HRMS (ESI) calcd for C32H45N3NaO7 ([MþNa]þ) 606.3155, found
606.3144.
d
8.08 (d, J¼8.2 Hz, 1H), 7.60 (d, J¼6.4 Hz, 1H), 7.27e7.20 (m, 2H),
5.23 (t, J¼5.0 Hz, 1H), 4.93 (br s, 1H), 3.93 (br s, 1H), 3.75 (d,
J¼5.0 Hz, 2H), 3.62 (br s, 1H), 3.55 (br s, 1H), 2.91e2.89 (m, 2H), 2.44
(br s, 1H), 1.76 (s, 3H), 1.71 (s, 3H), 1.66 (s, 9H), 1.43 (s, 9H); 13C NMR
(CDCl3, 100 MHz)
d
156.1, 150.3, 137.5, 135.9, 132.5, 129.7, 123.6,
4.1.23. Tryprostatin B (2). A solution of 68 (1.04 g, 1.78 mmol) in N-
methyl-2-pyrrolidinone (4.45 mL) was heated at reflux for 1.5 h.
After cooling to room temperature, the resulting solution was
purified with flash reverse-phase column chromatography (C-18,
50%e70% MeOH in H2O) to remove NMP. The residue was purified
with flash column chromatography on silica gel (hexane/EtOAc¼2/1)
122.6, 122.0, 118.4, 115.2, 114.5, 83.7, 79.5, 63.9, 52.4, 28.3, 28.1, 25.8,
25.6, 18.1, 18.1; HRMS (ESI) calcd for C26H38N2NaO5 ([MþNa]þ)
481.2678, found 481.2672.
4.1.21. (S)-3-(1-(tert-Butoxycarbonyl)-2-(3-methylbut-2-enyl)-in-
dol-3-yl)-2-(tert-butoxycarbonylamino)propanoic acid (66). To
a
to afford tryprostatin B (2) (559 mg, 1.59 mmol, 89%) as a yellow
24
stirred solution of 65 (1.08 g, 2.36 mmol) and iodobenzene diac-
etate (2.28 g, 7.08 mmol) in MeCN (5.9 mL) and phosphate buffer
(pH 6.8) (5.9 mL) was added 2,2,6,6-tetramethyl- piperidine-1-oxyl
(TEMPO) (36.8 mg, 0.236 mmol) at room temperature. After
30 min, saturated aq NaHCO3 was added to the reaction mixture
and the aqueous phase was extracted with EtOAc three times. The
combined organic layer was washed with brine, dried over Na2SO4,
filtered, and concentrated in vacuo. The residue was purified with
solid. Mp 100e102 ꢀC; [
a]
D
ꢁ71 (c 0.78, CHCl3); IR (neat, cmꢁ1
)
3283, 2926, 1668, 1657, 1459, 1438, 1422; 1H NMR (CDCl3, 400 MHz)
d
8.04 (br s,1H), 7.48 (d, J¼7.8 Hz, 1H), 7.32 (d, J¼7.8 Hz, 1H), 7.16 (dd,
J¼7.8, 6.9 Hz, 1H), 7.10 (dd, J¼7.8, 6.9 Hz, 1H), 5.63 (br s, 1H), 5.31 (t,
J¼7.4 Hz, 1H), 4.37 (dd, J¼11.4, 2.3 Hz, 1H), 4.07 (dd, J¼7.8, 7.4 Hz,
1H), 3.71e3.53 (m, 3H), 3.47 (m, 2H), 2.96 (dd, J¼14.6, 11.4 Hz, 1H),
2.37e2.31 (m, 1H), 2.10e1.99 (m, 2H), 1.95e1.89 (m, 1H), 1.79 (s, 3H),
1.75 (s, 3H); 13C NMR (CDCl3, 100 MHz)
d 169.3, 165.8, 136.4, 135.4,
flash column chromatography on silica gel (hexane/EtOAc¼7/3) to
135.3,127.9,121.7,119.8,119.7,117.7,110.7,104.5, 59.2, 54.5, 45.3, 28.3,
25.7, 25.5, 25.0, 22.6, 17.9; HRMS (ESI) calcd for C21H25N3NaO2
([MþNa]þ) 374.1845, found 374.1841.
24
afford 66 (1.01 g, 2.14 mmol, 91%) as a colorless oil. [
a]
þ25 (c
D
1.00, CHCl3); IR (neat, cmꢁ1) 3316, 2978, 2930, 2855, 1730, 1457,
1368, 1325, 1165, 1134; 1H NMR (CDCl3, 400 MHz) (3:1 mixture of
two rotamers) (major)
d
8.07 (d, J¼7.8 Hz, 1H), 7.50 (d, J¼6.9 Hz,
4.1.24. 2-Iodo-5-methoxyaniline (69). To a stirred solution of 4-
iodo-3-nitroanisole (6.33 g, 22.7 mmol) in acetic acid (3.78 mL)
and anhydrous EtOH (37.8 mL) were added Fe (7.60 g, 0.136 mol)
and FeCl3 (2.21 g, 13.6 mmol) portionwise at room temperature,
and then the mixture was heated to 80 ꢀC. After 40 min, the re-
action mixture was filtered through a pad of Celite. To the resulting
mixture was added H2O and the aqueous layer was extracted with
EtOAc three times. The combined organic layer was washed with
brine, dried over Na2SO4, filtered, and concentrated in vacuo. The
residue was purified with flash column chromatography on silica
gel (hexane/EtOAc¼7/1) to afford 69 (4.77 g, 19.2 mmol, 84%) as
a slightly yellow solid. Mp 33e34 ꢀC; IR (neat, cmꢁ1) 3459, 3364,
1H), 7.27e7.19 (m, 2H), 5.22 (br s, 1H), 5.03 (d, J¼6.0 Hz, 1H), 4.52
(br s, 1H), 3.79e3.64 (m, 2H), 3.29 (dd, J¼14.6, 4.6 Hz, 1H),
3.13e3.08 (m, 1H), 1.76 (s, 3H), 1.71 (s, 3H), 1.66 (s, 9H), 1.38 (s, 9H)
(minor)
d
8.07 (d, J¼7.8 Hz, 1H), 7.50 (d, J¼6.9 Hz, 1H), 7.27e7.19 (m,
2H), 5.22 (br s, 1H), 5.03 (d, J¼6.0 Hz, 1H), 4.52 (br s, 1H), 3.79e3.64
(m, 2H), 3.29 (dd, J¼14.6, 4.6 Hz,1H), 2.96 (br s,1H),1.76 (s, 3H),1.71
(s, 3H), 1.66 (s, 9H), 1.38 (s, 9H); 13C NMR (CDCl3, 100 MHz) (major)
d
175.8, 155.5, 150.3, 138.3, 135.9, 132.7, 129.4, 123.7, 122.6, 121.8,
118.1, 115.3, 112.8, 83.8, 80.2, 54.6, 29.4, 28.2, 28.1, 27.4, 25.8, 18.1
(minor) 176.8, 156.5, 150.3, 137.9, 136.0, 132.1, 129.7, 123.6, 122.6,
d
122.0, 117.9, 115.3, 113.9, 83.6, 81.0, 53.7, 29.4, 28.2, 28.1, 26.8, 25.5,
18.2; HRMS (ESI) calcd for C26H36N2NaO6 ([MþNa]þ) 495.2458,
found 495.2457.
2936, 1613, 1569, 1486, 1428, 1332; 1H NMR (CDCl3, 400 MHz)
(d, J¼8.7 Hz, 1H), 6.32 (d, J¼2.8 Hz, 1H), 6.13 (dd, J¼8.7, 2.8 Hz, 1H),
4.06 (s, 2H), 3.74 (s, 3H); 13C NMR (CDCl3, 100 MHz)
161.1, 147.6,
d 7.47
d
4.1.22. tert-Butyl 3-((S)-2-(tert-butoxycarbonylamino)-3-((S)-2-(me-
thoxycarbonyl)pyrrolidin-1-yl)-3-oxopropyl)-2-(3-methylbut-2-enyl)-
139.2, 106.6, 100.5, 73.4, 55.3; HRMS (DART) calcd for C7H9INO
([MþH]þ) 249.9729, found 249.9738.
indole-1-carboxylate (68). To
2.14 mmol) and -proline methyl ester p-toluenesulfonate 67
(482 mg, 2.78 mmol) in CH2Cl2 (10.7 mL) were added HATU (1.06 g,
2.78 mmol) and N,N-diisopropylethylamine (932 L, 5.35 mmol) at
a stirred solution of 66 (1.01 g,
L
4.1.25. N-(2-Iodo-5-methoxyphenyl)formamide (70). A mixture of
formic acid (2.51 mL, 66.5 mmol) and acetic anhydride (3.39 mL,
33.2 mmol) was stirred at 50 ꢀC for 1 h and then cooled to 0 ꢀC. This
m