J.-W. Zhu et al. / Bioorg. Med. Chem. 8 (2000) 455±463
461
1
was used to record IR spectra (as KBr ®lms). H and
1
reaction mixture was neutralized with aqueous hydro-
gen chloride followed by extraction with ethyl acetate.
The organic layer was washed with brine and dried with
anhydrous sodium sulfate. After the solvent was evapor-
ated, the residue was puri®ed by silica gel chromatog-
raphy with 1% methanol in dichloromethane to aord
two compounds, 4,7-di-O-acetyl BFA (TX-1856, 18 mg,
28%) and 4-O-acetyl BFA (TX-1872, 24 mg, 42%) (TX-
3
C NMR spectra were observed in the indicated deut-
erated solvents with a JEOL JNM-EX400 spectrometer.
Chemical shifts are reported in ppm (d) down®eld from
tetramethylsilane as internal standard, with peak multi-
plicities being indicated as follows: s, singlet; d,
doublet; m, multiplet; dd, double of doublet. Mass
spectra were obtained on a Shimazu GC±MS QP-1000
mass spectrometer (direct insertion probe). Melting
points were obtained with Yanagimoto apparatus and
were uncorrected.
1856:TX-1872=43:57). R in dichloromethane:methanol
f
(9:1) were 0.76 (TX-1856) and 0.39 (TX-1872), respec-
ꢀ
tively. TX-1872, mp 106±107 C (white needle from
1
methanol±hexane); H NMR (CDCl ): d 7.25 (dd, 1H,
3
TX-1852 (7-oxo-BFA), TX-1853 (tetrahydro-BFA), TX-
J=4.4, 16.4 Hz), 5.70 (m, 2H), 5.28 (m, 2H), 4.85 (m,
1H), 4.32 (m, 1H), 2.42 (m, 1H), 2.26±2.13 (m, 2H), 2.12
(s, 3H), 2.03±1.48 (m, 9H, including 1H of OH), 2.24 (d,
1
(
855 (5,6-dehydro-2,3-dihydro-4,7-dioxo-BFA), TX-1856
4,7-di-O-acetyl-BFA), and TX-1891 (7-O-acetyl-BFA)
were synthesized with the methods described pre-
3H, J=6.4 Hz), 0.93 (m, 1H); 13C NMR (CDCl ): d
3
2
7
viously. The structures of these compounds were
1
170.06, 165.74, 147.30, 136.37, 130.61, 118.23, 76.26,
75.84, 72.11, 49.47, 44.31, 43.22, 40.95, 34.07, 31.80, 26.70,
13
identi®ed by H and C NMR spectra.
2
1376, 1236, 1070, 1013, 977 cm ; MS m/z 322 (M ).
6.52, 20.87; FT-IR: nmax 3457, 2934, 1742, 1715, 1451,
1 +
�
Synthesis of 4-oxo-BFA (TX-1933). To a solution of
BFA (20 mg, 71.3 mmol) in dichloromethane (3 mL) was
added manganese dioxide (195 mg, 2.2 mmol). The mix-
ture was stirred for 2 h at rt, ®ltered on Celite with ethyl
acetate. The solvent was removed by evaporation in
vacuum and the residue was puri®ed by chromatography
on silica gel eluted with dichloromethane:methanol
Synthesis of di-O-methyl-BFA (TX-1869) and 4-O-methyl-
BFA (TX-1870). To a solution of BFA (50 mg,
0.178 mmol) in DMF (1.0 mL) was added iodomethane
(100mL, 1.60mmol) and silver oxide (248mg, 1.07mmol).
The reaction mixture was stirred at rt overnight and
then ®ltered. The ®ltrate was evaporated and the residue
was separated by silica gel chromatography with ethyl
acetate:hexane (1:1) to give di-O-methyl-BFA (TX-
1869, 20 mg, 36%) and 4-O-methyl-BFA (TX-1870,
(
30:1) to give less polar fraction 4-oxo-BFA (TX-
6
2
1933), as a colorless oil (8.6 mg, 43%) and polar one,
unreacted BFA (8.2 mg, 41%). TX-1933, H NMR
1
(
CDCl ): d 7.77 (d, 1H, J=15.6 Hz), 6.45 (d, 1H,
3
J=16.0 Hz), 5.86 (m, 1H), 5.56 (dd, 1H, J=9.2 and
5.6 Hz), 4.66 (m, 1H), 4.32 (m, 1H), 2.98 (dd, 1H,
J=8.8 and 18.0 Hz), 2.60 (m, 1H), 2.30±1.77 (m, 8H,
12 mg, 23%) (TX-1869:TX-1870=64:36). R in ethyl
f
1
acetate:hexane (3:1) were 0.86 (TX-1869) and 0.64 (TX-
ꢀ
1870), respectively. TX-1869, mp 64±65 C (white amor-
1
including 1H of OH), 1.60 (m, 2H), 1.33 (d, 3H,
1
phous from methanol±hexane); H NMR (CD OD): d
3
3
J=6.0 Hz), 1. 21 (m, 1H); C NMR (CDCl ): d 200.75,
7.15 (dd, 1H, J=3.6, 15.6 Hz), 5.79±5.67 (m, 2H), 5.17
(dd, 1H, J=9.6, 15.2 Hz), 4.88 (m, 1H), 3.80 (m, 1H),
3.66 (m, 1H), 3.35 (s, 3H), 3.26 (s, 3H), 2.36 (m, 1H),
2.12 (m, 2H), 1.98 (m, 1H), 1.84±1.67 (m, 4H), 1.57 (m,
2H), 1.45 (m, 1H), 1.23 (d, 3H, J=6.4 Hz), 0.90 (m,
3
166.18, 140.25, 135.90, 132.88, 128.29, 73.76, 72.09,
5
6.18, 45.46, 42.57, 35.55, 34.25, 32.21, 25.55, 20.26;
3432, 2926, 2855, 1718, 1702, 1258, 1064,
80 cm ; MS m/z 278 (M ).
FT-IR: n
9
max
1
�
+
1
118.76, 115.29, 85.62, 80.96, 71.73, 57.71, 56.44, 50.44,
H); 13C NMR (CDCl ): d 166.33, 149.25, 130.10,
3
Synthesis of 4-epi-BFA (TX-1923). 4-oxo-BFA (5.5 mg,
ꢀ
2
0 mmol) in THF was cooled to � 78 C and then l-
44.15, 40.33, 37.38, 34.24, 31.75, 26.44, 20.81; MS m/z
ꢀ
+
Selectride (1.0 M solution in tetrahydrofuran) 42 mL
308 (M ). TX-1870, mp 94±95 C (white amorphous
1
ꢀ
the reaction was quenched by the addition of acetone,
warmed up to 0 C, and then to rt. The solution was
(
42 mmol) was added. After stirring at � 78 C for 2.5 h,
from methanol±hexane); H NMR (CDCl ): d 7.08 (dd,
3
1H, J=3.7, 15.9 Hz), 5.87 (dd, 1H, J=1.5, 16.1 Hz),
5.63 (m, 1H), 5.24 (dd, 1H, J=9.8, 15.1 Hz), 4.93 (m,
1H), 4.29 (m, 1H), 3.54 (m, 1H), 3.35 (s, 3H), 2.29 (m,
1H), 2.15 (m, 1H), 2.06±1.85 (m, 3H), 1.82±1.57 (m, 5H,
including 1H of OH), 1.54±1.44 (m, 2H), 1.26 (d, 3H,
ꢀ
neutralized by aqueous hydrogen chloride followed by
extraction with ethyl acetate. After evaporation, the
residue was separated on preparative TLC in diethyl
ether:acetone (1:5) to aord 4-epi-BFA (TX-1923, Rf
J=6.4 Hz), 0.90 (m, 1H); 13C NMR (CDCl ): d 166.24,
3
0
.48, 2.1 mg, 38%) and BFA (R 0.35, 2.9 mg, 52%) (4-
f
149.16, 136.36, 130.17, 118.87, 85.45, 72.46, 71.60,
57.76, 50.71, 44.35, 43.36, 41.35, 34.25, 31.84, 26.48,
+
20.89; MS m/z 294 (M ).
1
epi-BFA:BFA=2:3). TX-1923, H NMR (CDCl ): d
3
7.12 (dd, 1H, J=8.8, 15.6 Hz), 5.73 (d, 1H, J=15.6 Hz),
5.66 (m, 1H), 5.26 (dd, 1H, J=9.7, 15.6 Hz), 4.88 (m,
1H), 4.32 (m, 1H), 4.19 (m, 1H), 2.76 (m, 1H), 2.06±1.70
Synthesis of BFA seco-acid (TX-1875). A solution of
BFA (20 mg, 71.3 mmol) in 10% aqueous potassium
hydroxide (1.0 mL) was re¯uxed for 1 h and then neu-
tralized with iced 10% aqueous hydrogen chloride fol-
lowed by extracttion with ethyl acetate. The organic
layer was dried with anhydrous sodium sulfate and the
solvent was evaporated to give a colorless oil, BFA
(
m, 10H, including 2H of OH), 1.35 (m, 2H), 1.24 (d,
3
1
8
H, J=6.3 Hz), 0.91 (m, 1H); FT-IR: nmax 3367, 2928,
712, 1644, 1449, 1292, 1257, 1111, 1078, 1002, 986,
�
1
+
04 cm ; MS m/z 280 (M ).
Synthesis of 4-O-acetyl-BFA (TX-1872). The solution of
BFA (50 mg, 0.178 mmol) and acetic anhydride (18 mL,
1
seco-acid (TX-1875, 18 mg, 90%). TX-1875, H NMR
(CD OD): d 6.94 (dd, 1H, J=4.4, 15.6 Hz), 5.97 (dd,
0.19mmol) in pyridine (1.5 mL) was re¯uxed for 4 h. The
3