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E. Loeser et al. / Tetrahedron Letters 43 (2002) 2161–2165
J=1.9 Hz), 7.35 (2H, dt, J=8.1, 1.9 Hz), 7.07 (2H, ddd,
4.7, 0.8 Hz), 1.85 (6H, s); 13C NMR (75.5 MHz, DMSO)
l 148.1, 147.8, 135.8, 133.6, 122.5, 66.1, 20.8. ESI-MS
calcd for C14H14N2O 226.11, found [M+H]+ 227. 12t: Mp
J=8.1, 4.7, 0.6 Hz), 5.42 (2H, s), 1.61 (6H, s); 13C NMR
(75.5 MHz, DMSO) l 148.6, 147.1, 141.5, 134.7, 121.8,
76.1, 24.5. ESI-MS calcd for C14H16N2O2 244.12, found
[M+H]+ 245.
1
107–109°C, H NMR (300 MHz, DMSO) l 8.71 (2H, dd,
J=2.3, 0.9 Hz), 8.59 (2H, dd, J=4.7, 1.7 Hz), 7.66 (2H,
ddd, J=7.9, 2.3, 1.7 Hz), 7.34 (2H, ddd, J=7.9, 4.7, 0.9
Hz), 1.33 (6H, s); 13C NMR (75.5 MHz, DMSO) l 148.9,
148.0, 136.2, 133.9, 123.2, 66.5, 21.5. ESI-MS calcd for
C14H14N2O 226.11, found [M+H]+ 227.
4. Pure samples of the monosulfates and disulfates were
obtained by adding 7.0 g of 1r or 1m to a cooled mixture
of 50 g of concentrated H2SO4 and 50 g of fuming H2SO4.
The reaction was added to stirred ice water (800 g). The
mixture was brought to pH 9–10 with 30% aq. NH3 (ꢀ150
mL). After evaporation of water, the solids were triturated
in EtOH (200 mL) and the ammonium sulfate filtered off.
The filtrate was evaporated, and pure samples were iso-
lated using a reversed-phase column (C-18 silica gel, 0–
20% MeCN/water). Since only the purest fractions were
isolated, yields are not reported. Drying under high vac-
6. HPLC conditions: Waters Symmetry C-18 column, 4.6×
250 mm; gradient 0% B to 100% B in 11 min, A=95:5
(v/v) 0.1% NH4OAc/MeCN, B=95:5 (v/v) MeCN/H2O;
flow rate, 1.2 mL/min; detection, UV 260 nm. Reaction
samples were quenched by adding to rapidly stirred ice
cold water, then neutralizing with Na2HPO4 before injec-
tion. Ret. times (min): 1, 6.0; 2r, 5.1; 2m, 5.4 3r, 2.9; 3m,
3.0; 4, 8.1; 5, 7.1; 6, 5.8 and 6.2; 7, 8.8; 8, 7.5; 9, 3.6; 10,
5.3, 11, 4.9. To separate 1r and 1m, the gradient was
changed to 40% B to 100% B in 10 min, A=95:5 (v/v)
0.1% NH4OAc/MeCN, B=90:10 (v/v) 0.05% HOAc/
MeCN. Ret. times (min): 1r, 4.3; 1m, 4.6.
1
uum gave glassy solids which appeared by H NMR in all
cases to be partially hydrated ammonium and inner salt
mixtures typically showing an ammonium signal at about
7.1 ppm (t, J=49 Hz) and a broad signal at about 3.5–4.5
ppm. These signals are not included in the spectral data
1
below. 2r: H NMR (300 MHz, DMSO) l 8.29–8.26 (2H,
7. To obtain samples of compounds 4–7 and 9 for character-
ization, 9.2 g of 1m was stirred in concentrated H2SO4
(100 mL) for 70 h. The reaction was intentionally stopped
before completion so that samples of intermediates could
be isolated as well as final products. HPLC before workup
indicated that about 10% of 1m and 2m remained unre-
acted, and the major products were 4 (20%), 5 (29%), 7
(15%), and 9 (21%) with minor amounts of 6 and 10
(<3%). After quenching on ice and neutralization of acid
with 30% NH3, compounds 4, 5, and 7 were extracted into
toluene and isolated using chromatography (C-18 silica
gel, 5–50% MeCN). Compounds 4, 5 and 7 are known2
and showed satisfactory spectral analysis. Isolated yields
were 1.9 g (22%), 3.2 g (38%), and 1.0 g (13%), respec-
tively. The water-soluble compounds 6 and 9 were chro-
matographed separately (C-18 silica gel, 0 to 30% MeCN)
and samples isolated as ammonium salts. Compound 6
appeared by 1H NMR to exist as major and minor iso-
mers, which could be partially separated by chromatogra-
phy and were isolated in amounts of only about 50 and 30
mg, respectively. Compound 9 (1.8 g) was isolated from
the purest fractions and another estimated 0.4 g was
present in impure fractions, giving a total yield of about
14%. Samples of compounds 10 and 11 were prepared
separately by the action of H2SO4+fuming H2SO4 on
compound 5 and were isolated by reversed-phase chro-
matography. Compound 11 appeared by 1H NMR and
HPLC to be only one isomer.
m), 8.11 (2H, d, J=2.1 Hz), 7.39–7.31 (2H, m), 7.15–7.11
(2H, m), 5.68 (1H, s), 2.03 (3H, s), 1.66 (3H, s); 13C NMR
(75.5 MHz, DMSO) l 148.1, 147.6, 146.7, 145.7, 141.3,
140.1, 136.9, 135.7, 122.1, 121.9, 84.4, 76.2, 24.6, 18.8.
ESI-MS calcd for C14H16N2O5S: 324.08, found [M+H]+
325. 2m: 1H NMR (300 MHz, DMSO) l 8.69 (1H, d,
J=1.9 Hz), 8.60 (1H, d, J=1.7 Hz), 8.44–8.40 (2H, m),
7.94–7.85 (2H, m), 7.36–7.32 (2H, m), 5.37 (1H, s), 1.60
(3H, s), 1.24 (3H, s); 13C NMR (75.5 MHz, DMSO) l
148.8, 148.5, 147.0, 146.3, 141.8, 139.9, 137.2, 136.0, 122.6,
122.1, 84.4, 75.9, 25.2, 20.0. ESI-MS calcd for
C14H16N2O5S: 324.08, found [M+H]+ 325. 3r: 1H NMR
(300 MHz, DMSO) l 8.25 (2H, dd, J=4.9, 1.7 Hz), 8.06
(2H, d, J=1.7 Hz), 7.25 (2H, dt, J=7.9, 1.7 Hz), 7.07 (2H,
dd, J=7.9, 4.9 Hz), 2.05 (6H, s); 13C NMR (75.5 MHz,
DMSO) l 148.3, 146.2, 139.5, 136.6, 121.7, 83.9, 19.1.
ESI-MS calcd for C14H16N2O8S2: 404.03, found [M+NH4]+
422, [M+H]+ 405, [MH−SO3]+ 325. 3m: 1H NMR (300
MHz, DMSO) l 8.67 (2H, d, 1.7 Hz), 8.48 (2H, dd,
J=5.1, 1.7 Hz), 8.02 (2H, dt, J=7.9, 1.7 Hz), 7.47 (2H,
dd, J=7.9, 5.1 Hz), 1.60 (6H, s); 13C NMR (75.5 MHz,
DMSO) l 147.5, 145.2, 140.1, 138.9, 122.8, 83.6, 19.9.
ESI-MS calcd for C14H16N2O8S2: 404.03, found [M+NH4]+
422, [M+H]+ 405, [MH−SO3]+ 325.
5. The position of SO3 addition was indicated by: (a) signifi-
cant changes in the 13C NMR chemical shifts of the
tertiary carbons; (b) the presence of only one hydroxyl
signal in the 1H NMR spectra of 2 and the complete
absence of hydroxyl signals in 3, and (c) the reaction of 2r
and 2m in 0.5 M NaOH which cleanly forms the cis and
trans epoxides while compounds 1 and 3 did not react
under NaOH conditions.
Analytical data. 6: Major isomer; 1H NMR (300 MHz,
D2O) l 8.29 (2H, brd, J=4.9 Hz), 8.18 (2H, bd, J=1.9
Hz), 7.76–7.70 (2H, m), 7.38–7.32 (2H, m), 5.11 (2H, s),
2.36 (3H, s). ESI-MS calcd for C14H14N2O4S: 306.07,
found [M+H]+ 307. Minor isomer; 1H NMR (300 MHz,
D2O) l 8.58–8.54 (4H, m), 7.99–792 (2H, m), 7.62–7.55
(2H, m), 4.61 (2H, s), 1.96 (3H, s). ESI-MS calcd for
C14H14N2O4S: 306.07, found [M+H]+ 307. 8 could not be
isolated and was identified by HPLC-MS analysis of reac-
tion mixtures; ESI-MS calcd for C14H12N2O3S: 288.06,
found [M+H]+ 289. 9: 1H NMR (300 MHz, D2O) l
8.74–8.63 (4H, bm), 8.23 (1H, dt, J=8.1, 1.7 Hz), 8.14
(1H, dt, J=8.1, 1.7 Hz), 7.78 (1H, dd, J=8.1, 5.3 Hz),
7.73 (1H, dd, J=8.1, 5.3 Hz), 4.69 (2H, s), 3.97 (2H, s);
12c: Mp 40–46°C, 1H NMR (300 MHz, DMSO) l 8.41
(2H, dd, J=2.3, 0.8 Hz), 8.27 (2H, dd, J=4.7, 1.9 Hz),
7.40 (2H, ddd, J=7.9, 2.3, 1.9 Hz), 7.01 (2H, ddd, J=7.9,