Cho et al.
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5.25 (d, 1H, J=7 Hz), 6.82-6.95 (m, 5H), 7.08 (d, 1H, J=8 Hz),
7.48 (t, 2H, J=8 Hz), 7.61 (t, 1H, J=7 Hz), 8.18 (d, 2H, J=7.5Hz,
aromatic); 13C NMR 13.9, 55.9, 59.1, 61.1, 74.8, 111.1, 112.1,
190.0, 121.5, 122.5, 126.8, 128.5, 129.5, 130.3, 133.4, 139.6, 139.8,
148.8, 151.1, 164.6, 172.7; HRMS (ES) m/z 503.1686 (M þ Na,
C27H28O8Na requires 503.1682).
96% conversions of the respective substrates). The resulting
mixtures were concentrated in vacuo and subjected to HPLC
analysis to give the following yields. From 4T: VAD (95%), 6
(25%), and 18 (trace); from 4E: VAD (95%), 6 (46%), and 18
(trace); from 8E: VAD (88%), 3 (trace), 17 (7%) and 19 (4%);
from 8T: VAD (31%), 3 (trace), 17 (32%), and 19 (33%).
19: 1H NMR 3.91 (s, 3H), 3.92 (s, 3H), 3.95 (s, 3H), 4.09-4.17
(m, 2H), 5.60-5.62 (m, 1H), 6.90-6.94 (m, 2H), 7.56 (d, 1H, J=
2.00 Hz), 7.69-7.71 (m, 2H), 7.92-7.94 (m, 1H); 13C NMR
29.7, 56.0, 56.2, 56.4, 63.7, 83.1, 110.2, 110.8, 110.9, 111.7, 119.5,
123.4, 127.6, 141.2, 146.6, 149.5, 154.4, 155.5, 193.3; HRMS
(ES) m/z 400.1008 (M þ Na, C18H19NO8Na requires 400.1004).
CAN Reaction of 17. A 50 mL MeCN solution containing 17
(300 mg, 0.9 mol) and CAN (1.0 mg, 1.8 mmol) was stirred for 13
h at room temperature (ca. 60% conversion of 17). The resulting
mixture was concentrated in vacuo, and the residue was sub-
jected to column chromatography to yield 187 mg (55%) of 19.
CAN Reactivity of 4T, 4E, 8E, and 8T. The absorbances at
390 nm of independent solutions of 4T, 4E, 8E, and 8T (1.25 ꢀ
10-4 M) containing CAN (2.5 ꢀ 10-4 M) in 3.0 mL of MeCN
were monitored 30 min after mixing. A plot of absorbance
versus time is shown in Figure 5S (Supporting Information).
In a stopped flow apparatus, MeCN solutions of CAN (3.0ꢀ
10-4 M) were added to solutions containing five different
1
14E: H NMR 1.23 (t, 3H, J = 7.00 Hz,), 3.16 (s, 1H), 3.65
(s, 3H), 3.76 (s, 3H), 3.80 (s, 3H), 3.74 (d, 1H, J = 7.00 Hz),
4.15-4.26 (m, 2H), 5.12 (d, 1H, J = 9.50 Hz), 6.57-6.76 (m,
5H), 6.94 (d, 1H, J = 8.50 Hz), 7.47 (t, 2H, J = 8.00 Hz), 7.59
(t, 1H, J=7.50 Hz), 8.15 (d, 2H, J=7.00 Hz); 13C NMR 14.1,
55.8, 55.9, 59.7, 61.2, 76.4, 110.7, 111.1, 111.9, 118.9, 120.7,
122.3, 127.6, 128.5, 129.4, 130.2, 133.4, 139.4, 139.9, 148.5,
148.8, 151.0, 164.5, 173.4; HRMS (ES) m/z 503.1672 (M þ
Na, C27H28O8Na requires 503.1682).
threo-1-(4-Hydroxy-3-methoxyphenyl)-2-(3,4-dimethoxyphenyl)-
1,3-diol Acetonide (15T). To solution of THF (60 mL) containing
1.0 M LiAlH4 (22.9 mL, 22.9 mmol) was added 14T (5.5 g, 11.4
mmol) at room temperature. After 3 h of stirring, H2O (20 mL) and
1 N HCl (20 mL) were added at 0 °C, and the solution was extracted
with CH2Cl2. The organic extracts were dried and concentrated in
vacuo, giving a solid residue that was crystallized from diethyl ether
to give the known57m-p,97 diol (2.7 g, 70%). 1H NMR 3.05 (q, 1H,
J=6.50 Hz), 3.74 (d, 2H, J=6.00 Hz,), 3.82 (s, 3H), 3.83 (s, 3H),
3.86 (s, 6H), 4.89 (d, 1H, J = 7.00 Hz), 5.56 (s, 1H), 6.73-6.86
(m, 6H).
A solution of the diol (1.0 g, 3.0 mmol) in CH2Cl2 (40 mL)
containing pyridinium p-toluenesulfonate (0.15 g, 0.6 mmol)
and 2,2-dimethoxypropane (1.6 g, 15.0 mmol) was stirred at
room temperature for 8 h and concentrated in vauco to give a
residue that was portioned between EtOAc and satd NaHCO3.
The organic layer was dried and concentrated in vacuo to give a
residue, which was subjected to column chromatography
(EtOAc/hexane 1:3) to yield 15T (0.72 g, 64%). Crystallization
of the substance in 1:10 CHCl3/diethyl ether gave transparent
crystals of 15T. 1H NMR 1.62 (s, 3H), 1.65 (s, 3H), 3.04 (s, 3H),
3.73 (s, 3H), 3.79 (s, 3H), 3.83 (dd, 1H, J=14.80 Hz, J=21 Hz),
4.10 and 4.53 (two d, 2H, J = 11.50 Hz), 5.39 (s, 1H), 6.30 (s,
1H), 6.59-6.72 (m, 4H), 6.97 (s, 1H); 13C NMR 18.8, 29.9, 45.2,
55.7, 55.8, 65.4, 73.8, 99.4, 109.3, 110.2, 113.3, 113.5, 119.0,
122.1, 132.4, 132.6, 144.5, 146.0, 147.4, 147.9; HRMS (ES) m/z
397.1627 (M þ Na, C21H26O6Na requires 397.1630).
concentrations of 4T, 4E, 8E, and 8T (7.5 ꢀ 10-5, 3.75 ꢀ 10-5
,
1.5ꢀ10-5, 7.5ꢀ10-6, 3.75ꢀ10-6 M). Changes in absorbances at
λ
390 (for CAN, λ390 nm=2840) of these solutions over a 0.1-0.25
s period were monitored. From plots of time versus absorbance,
initial slopes corresponding to ΔA390 versus t (0.1-0.25 s) of
each reaction were obtained. These ΔA390 values were converted
to concentration changes (ΔClignin), and reaction rates (v) of
each reaction were determined by using the following equations:
ΔC = ΔACAN/ε390 nm and v = ΔClignin/0.15. From plots of v
versus concentrations (Figure 6), the rate constants (k) of CAN
reaction of each compound were determined (Table 4).
In a stopped flow apparatus, MeCN solutions of 4T, 4E, 8E,
and 8T (3.75 ꢀ 10-4 M) containing six different concentrations
of CAN (1.5ꢀ10-4, 1.8ꢀ10-4, 2.1ꢀ10-4, 2.4ꢀ10-4, 3.0ꢀ10-4
,
and 3.6 ꢀ 10-4 M). Changes in absorbances at λ390 (for CAN,
λ
390 nm ε=2840) of these solutions over a 0.1-0.25 s period were
monitored. From plots of time versus absorbance, initial slopes
corresponding to ΔA390 versus t (0.1-0.25 s) of each reaction
were obtained. These ΔA390 values were converted to concen-
tration changes (ΔCCAN) and reaction rates (v) of each reaction
were determined by using the following equations: ΔC =
ΔACAN/2ε390 nm and v = ΔClignin. From plots of v versus con-
centrations (Figure 5), the rate constants of CAN reaction of
each compound were determined (Table 4).
Lignin Peroxidase Catalyzed Reactions of 4T, 4E, 8E, and 8T.
To 0.97 mL of 0.1 M tartrate buffer (pH 3.4) were added 10 μL of
each substrate 4T, 4E, 8E, and 8T (0.1 M, final concentration
200 μM) and 8 μL of H2O2 (1.25ꢀ10-2 M, final concentration
100 μM). After 15 μL of lignin peroxidase (0.15 unit, 0.36 μM)
was added, the solutions were agitated for 10 min and then
subjected to HPLC analysis to yield the following products
from 8E (35% conversion): VAD (35%), 3 (trace) and 17 (4%);
from 8T (66% conversion): VAD (31%), 3 (trace), and 17
(29%); from 4T (73% conversion): VAD (52%), 5 (trace), and
6 (14%); from 4E (77% conversion): VAD (45%), 5 (trace), and
6 (15%).
Lignin Peroxidase Reactivity of 4T, 4E, 8E, and 8T. In a
stopped flow apparatus, solutions of LP (1.8 μM) in tartrate
buffer (pH 3.4) containing H2O2 (50 μM) were mixed with
solutions containing 50, 100, 150, 200, 250, 375, 500, 750,
1000, 1500, and 2500 μM of 4T, 4E, 8E, and 8T. The absorbance
increases at 310 nm, corresponding to the formation of VAD
and keto-alcohols 6, 18 (for 4T and 4E), and 17 (for 8E and 8T)
were measured over a 0.1-1 s time period. The ΔA310 values
DCA-Sensitized Photoreactions of 8E, 8T, 4T, and 4E. General
Procedure. Seventy milliliters of degassed/N2-purged or oxgenated
solutions of satd DCA (0.27 mM) in 5% H2O/MeCN containing
the substrate (1.5ꢀ10-5 mol, 2.1 mM) was irradiated with uranium
glass filtered light for 7 h. The photolyzates were concentrated in
vacuo, and the residues were subjected to HPLC analysis.
Relative Quantum Yields of DCA-Promoted Photoreactions of
4T, 4E, 8E, and 8T. Independent DCA-saturated, N2-purged
solutions, containing 4T, 4E, 8E, and 8T (1.5 ꢀ 10-5 mol,
2.1 mM) in 7 mL of 5% aqueous MeCN in quartz test tubes were
simultaneously irradiated by using uranium glass filtered light
in a merry-go-round apparatus for 14 h. The solutions were
concentrated in vacuo, and the residues were diluted with 1.5 mL
CHCl3 solutions containing the standard 1,10-phenanthroline
(2ꢀ10-3 M final concentration). Concentration of each of these
solutions was followed by 1H NMR analysis (peak intensities of
VAD at 9.84 ppm (1H) vs 1,10-phenanthroline at 9.27 ppm
(2H)) to determine the quantities of VAD formed in the photo-
reactions.
CAN Reactions of 4T, 4E, 8E, and 8T. Individual solutions
containing the substrates 4T, 4E, 8E, and 8T (2.0 mg, 6.0ꢀ10-6
mol) and CAN (6.6 mg, 1.2ꢀ10-5 mol) in 12 mL of MeCN were
stirred for 15 h at room temperature (100%, 100%, 90%, and
(97) Ralph, J.; Ede, R. M.; Robinson, N. P.; Main, L. J. Wood Chem.
Technol. 1987, 7, 133.
J. Org. Chem. Vol. 75, No. 19, 2010 6561