K. Kai et al. / Phytochemistry 68 (2007) 1651–1663
1661
CD3OD): d 36.92, 37.04, 38.31, 38.39, 43.78, 44.01, 55.08,
55.22, 110.74, 123.31, 123.45, 125.21, 125.42, 127.78,
129.01, 129.11, 129.42, 129.49, 130.19, 130.39, 130.51,
138.25, 138.40, 143.13, 143.25, 172.71, 174.56, 181.57.
MS (ESI): m/z 321 [M+H]+.
J = 2.3 Hz), 9.18 (1H, br. s). 13C NMR (100 MHz,
CD3CN): d 1.80, 19.4, 31.3, 33.6, 58.4, 107.1, 110.2,
111.6, 120.8, 124.6, 127.2, 130.3, 143.8, 173.2, 172.9. MS
(ESI): m/z 291 [M+H]+.
OH-IAA-Phe (14, 28–30). MeO-IAAs (22) were individ-
ually condensed with L-phenylalanine t-butyl ester in the
presence of DCC and DMAP in pyridine at room temper-
ature overnight to give MeO-IAA-Phe-tBu (24) quantita-
tively. Deprotection with four equivalents of boron
tribromide in CH2Cl2 under Ar at ꢀ78 ꢁC for 4 h afforded
OH-IAA-Phe (28: 57%, 29: 70%, 14: 43%, 30: 27%). 4-OH-
OH-IAA-Val (13, 25–27). The scheme for synthesizing
4-OH-, 5-OH-, 6-OH-, and 7-OH-IAA-Val (25, 26, 13, 27)
is shown in Fig. 3. Treatment of methoxyindole (19) with
1.1 equivalents of oxalyl dichloride at 0 ꢁC for 2 h, and
subsequently excess MeOH for 4 h gave meth-
oxyindoleoxoacetic acid methyl ester (20) (4-MeO: 57%,
5-MeO: 95%, 6-MeO: 70%, 7-MeO: 87%). Reduction of
a-ketone with 0.4 equivalents (w/w) of 10% (w/w) palla-
dium on activated charcoal and 10 equivalents of NaH2-
PO2 Æ H2O in 1,4-dioxane–H2O at room temperature for
2 days afforded methoxyindole-3-acetic acid methyl ester
(MeO-IAA-OMe, 21) (4-MeO: 83%, 5-MeO: 94%, 6-
MeO: 74%, 7-MeO: 96%). Treatment of 21 with 1 M
KOH in THF–H2O gave MeO-IAA (22) quantitatively.
Condensation of 22 with L-valine methyl ester was con-
ducted with DCC and DMAP in pyridine at room tem-
perature overnight to give MeO-IAA-Val-OMe (23)
quantitatively. Demethylation using four equivalents of
boron tribromide in dichloromethane under Ar at
ꢀ78 ꢁC overnight afforded OH-IAA-Val (25: 38%, 26:
1
IAA-Phe (28). H NMR (400 MHz, CD3CN): d 2.95 (1H,
dd, J = 7.6, 13.9 Hz), 3.10 (1H, dd, J = 5.3, 13.9 Hz), 3.67
(2H, s), 4.62 (1H, m), 6.43 (1H, d, J = 7.4 Hz), 6.90–6.98
(3H, m), 7.02–7.03 (2H, m), 7.09–7.14 (2H, m), 7.22 (1H,
d, J = 7.5 Hz), 7.58 (1H, s), 9.11 (1H, br. s), 9.62 (1H, br.
s). 13C NMR (100 MHz, CD3CN): d 34.7, 37.6, 54.6,
104.8, 106.5, 108.1, 123.5, 124.0, 127.7, 129.2 (2), 130.2
(2), 137.4, 139.9, 151.8, 172.4, 175.4. MS (ESI): m/z 339
[M+H]+. 5-OH-IAA-Phe (29). 1H NMR (400 MHz,
CD3CN): d 2.92 (1H, dd, J = 7.4, 13.9 Hz), 3.04 (1H, dd,
J = 5.2, 13.9 Hz), 3.54 (2H, s), 4.60 (1H, dt, J = 5.2,
7.5 Hz), 6.53 (1H, d, J = 7.4 Hz), 6.71 (1H, dd, J = 2.2,
8.7 Hz), 6.86 (1H, d, J = 2.2 Hz), 6.95–6.97 (2H, m), 7.02
(1H, d, J = 2.0 Hz), 7.13–7.15 (3H, m), 7.24 (1H, d,
J = 8,7 Hz), 9.04 (1H, br. s). 13C NMR (100 MHz,
CD3CN): d 33.5, 37.6, 54.3, 103.6, 108.4, 112.8, 113.0,
125.9, 127.7, 129.3 (2), 130.2 (2), 132.3, 137.5, 151.5,
172.9 (2). MS (ESI): m/z 339 [M+H]+. 6-OH-IAA-Phe
(14). 1H NMR (400 MHz, CD3CN): d 2.92 (1H, dd,
J = 7.6, 13.9 Hz), 3.06 (1H, dd, J = 5.2, 13.9 Hz), 3.54
(2H, s), 4.60 (1H, dt, J = 5.2, 7.6 Hz), 6.53 (1H, d,
J = 6.8 Hz), 6.59 (1H, dd, J = 2.2, 8.5 Hz), 6.80 (1H, d,
J = 2.0 Hz), 6.90 (1H, d, J = 2.3 Hz), 6.97–6.99 (2H, m),
7.15–7.18 (4H, m), 7.22 (1H, d, J = 8.6 Hz), 8.94 (1H, br.
s). 13C NMR (100 MHz, CD3CN): d 33.5, 37.6, 54.2,
97.6, 109.2, 110.4, 120.2, 122.2, 123.6, 127.7, 129.3 (2),
130.2 (2), 137.6, 138.5, 154.1, 172.7, 172.9. MS (ESI): m/z
1
33%, 13: 26%, 27: 47%). 4-OH-IAA-Val (25). H NMR
(400 MHz, CD3CN): d 0.86 (3H, d, J = 7.1 Hz), 0.88
(3H, d, J = 7.0 Hz), 2.12 (1H, m), 3.74 (2H, d,
J = 1.9 Hz), 4.29 (1H, dd, J = 5.4, 8.3 Hz), 6.43 (1H, dd,
J = 1.0, 7.4 Hz), 6.91 (1H, dd, J = 1.0, 8.2 Hz), 6.97
(1H, dd, J = 7.5, 8.1 Hz), 7.03 (1H, d, J = 2.4 Hz), 7.25
(1H, d, J = 7.4 Hz), 9.10 (1H, br. s), 9.96 (1H, br. s).
13C NMR (100 MHz, CD3CN): d 18.0, 19.2, 31.2, 34.7,
58.5, 104.7, 106.5, 108.4, 123.3, 124.0, 139.9, 151.9,
172.6, 175.9. MS (ESI): m/z 291 [M+H]+. 5-OH-IAA-
1
Val (26). H NMR (400 MHz, CD3CN): d 0.79 (3H, d,
J = 6.9 Hz), 0.86 (3H, d, J = 6.8 Hz), 2.10 (1H, m), 3.68
(2H, s) 4.31 (1H, dd, J = 5.4, 8.2 Hz), 6.70 (1H, dd,
J = 2.3, 8.7 Hz), 6.82 (1H, br. s), 6.91 (1H, d,
J = 2.2 Hz), 7.14 (1H, d, J = 2.1 Hz), 7.24 (1H, d,
J = 8.7 Hz), 9.07 (1H, br. s). 13C NMR (100 MHz,
CD3CN): d 1.79, 19.3, 31.2, 33.3, 58.6, 103.5, 108.2,
112.8, 113.0, 126.0, 128.8, 132.3, 151.4, 172.9 (2). MS
1
339 [M+H]+. 7-OH-IAA-Phe (30). H NMR (400 MHz,
CD3CN): d 2.92 (1H, dd, J = 7.6, 13.9 Hz), 3.05 (1H, dd,
J = 5.1, 13.9 Hz), 3.60 (2H, s), 4.63 (1H, dt, J = 5.2,
7.7 Hz), 6.59 (1H, d, J = 7.5 Hz), 6.64 (1H, d,
J = 7.6 Hz), 6.84 (1H, dd, J = 7.7, 7.8 Hz), 6.94–6.96 (3H,
m), 7.00 (1H, d, J = 2.4 Hz), 7.13–7.15 (3H, m), 9.26 (1H,
br. s). 13C NMR (100 MHz, CD3CN): d 33.5, 37.6, 54.4,
107.3, 109.5, 111.5, 121.0, 124.9,127.3, 127.7, 129.3 (2),
130.2 (2), 130.3, 137.5, 143.9, 173.2, 173.3. MS (ESI): m/z
339 [M+H]+.
1
(ESI): m/z 291 [M+H]+. 6-OH-IAA-Val (13). H NMR
(400 MHz, CD3CN): d 0.78 (3H, d, J = 6.9 Hz), 0.85
(3H, d, J = 6.9 Hz), 2.07 (1H, m), 3.63 (2H, s), 4.27
(1H, dd, J = 5.4, 8.4 Hz), 6.61 (1H, dd, J = 2.2, 8.5 Hz),
6.64 (1H, d, J = 9.0 Hz), 6.80 (1H, d, J = 2.2 Hz), 7.02
(1H, d, J = 2.3 Hz), 7.35 (1H, d, J = 8.5 Hz), 8.97 (1H,
br. s). 13C NMR (100 MHz, CD3CN): d 1.80, 19.4, 31.2,
33.6, 58.4, 97.6, 109.5, 110.3, 120.2, 122.2, 123.5, 138.5,
154.1, 173.2, 173.4. MS (ESI): m/z 291 [M+H]+. 7-OH-
IAA-Val (27). 1H NMR (400 MHz, CD3CN): d 0.78
(3H, d, J = 6.9 Hz), 0.85 (3H, d, J = 6.9 Hz), 2.07 (1H,
m), 3.65 (2H, s), 4.26 (1H, dd, J = 5.5, 8.4 Hz), 6.58
(1H, dd, J = 0.6, 7.5 Hz), 6.62 (1H, br. s), 6.88 (1H, dd,
J = 7.7, 7.9 Hz), 7.08 (1H, d, J = 8.0 Hz), 7.14 (1H, d,
5.5. Deuterium-labeled compounds
[20,20-2H2]IAA-Asp (2-d2) and [20,20-2H2]IAA-Glu (3-d2)
were kindly supplied by Dr. J. Hiratake (Institute for
Chemical Research, Kyoto University). [20,20-2H2]6-OH-
IAA-Val (13-d2) and [20,20-2H2]6-OH-IAA-Phe (14-d2)
were deuterium-labeled according to the method of
Hiratake et al. with some modification (Hiratake et al.,