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4.1.1. 3-Hydroxy-dibenzo[b,d]pyran-6-one (3a).22 Brown
amorphous solid, yield, 56%, mp 235 ꢁC; MS: m=z 212
(Mþ); 1H NMR (CDCl3) d: 6.4–6.7 (m, 2H, H-2 and H-
4), 7.5–7.6 (t, 1H, H-8), 7.78–7.81 (t, 1H, H-9), 7.90–7.98
(m, 2H, H-7 and H-10), 8.33–8.35 (d, 1H, H-1).
4.1.9.
3,8-Dihydroxy-9-(2-pyrrolidin-1-yl-ethoxy)-di-
benzo[b,d]pyran-6-one (3i). A solution of compound 3f
(355 mg, 1 mM) in dry dichloromethane was cooled to
)78 ꢁC. Boron tribromide (1.0 M soln in CH2Cl2;
5 equiv 0.6 mL) was added dropwise via syringe and the
solution stirred at )78 ꢁC for 15 min, thereafter, it was
allowed to come to rt and left overnight. The reaction
mixture was poured in ice water, and extracted with
dichloromethane. Removal of excess solvent gave a
sticky solid, which was crystallised from chloroform/
methanol as white crystalline solid, yield 210 mg, mp
214 ꢁC; MS: m=z 341 (Mþ); 1H NMR (DMSO-d6)
d: 1.70–1.80 (m, 4H, (CH2)2), 2.50–2.57 (m, 4H,
N(CH2)2), 2.88–3.08 (t, 2H, NCH2), 4.30–4.36 (t, 2H,
OCH2), 6.73–6.79 (d, 1H, H-4), 6.84–6.86 (dd, 1H, H-2),
7.53 (s, 1H, H-7), 7.64 (s, 1H, H-10), 8.18–8.22 (s, 1H,
H-1), 9.13 (s, 1H, OH). Anal. Calcd for C19H19NO5: C,
66.85; H, 5.61; N, 4.10. Found C, 66.52; H, 5.45; N,
4.14.
4.1.2. 8,9-Dimethoxy 3-hydroxy-dibenzo[b,d]pyran-6-one
1
(3b). Yield 58%, mp > 280 ꢁC; MS: m=z 272 (Mþ); H
NMR (CDCl3) d: 3.88 (s, 3H, OCH3), 6.39 (s, 1H, H-4),
6.73–6.79 (dd, 1H, H-2), 7.42–7.46 (dd, 1H, H-9), 7.57
(s, 1H, H-7), 8.00–8.04 (d, 1H, H-1), 8.11–8.16 (d, 1H,
H-10).
4.1.3. 3,9-Dihydroxy-8-methoxy-dibenzo[b,d]pyran-6-one
(3c). Yield 290 mg (56%), mp > 280 ꢁC; MS: m=z 258
(Mþ); 1H NMR (CDCl3) d: 3.9 (s, 3H, OCH3), 6.72–6.73
(d, 1H, H-4), 6.79–6.85 (dd, 1H, H-2), 7.40 (s, 1H, H-
10), 7.50 (s, 1H, H-7), 7.88–7.92 (d, 1H, H-1).
4.1.10.
3,8-Dihydroxy-9-(2-piperidin-1-yl-ethoxy)-di-
benzo[b,d]pyran-6-one (3j). Yield 60%, mp 184 ꢁC; MS:
4.1.4. 9-Benzyloxy-3-hydroxy-8-methoxy-dibenzo[b,d]-
pyran-6-one (3d). Yield 80%, mp > 300 ꢁC; MS: m=z
348 (Mþ); 1H NMR (CDCl3) d: 3.91 (s, 3H, OCH3), 5.49
(s, 2H, OCH2), 6.86–6.87 (d, 1H, H-4), 6.94–6.98 (dd,
1H, H-2), 7.49–7.69 (m, 7H, H-7, H-10 and Ar-H), 7.93
(s, 1H, H-7), 8.26–8.30 (d, 1H, H-1).
1
m=z 355 ( Mþ); H NMR (DMSO-d6) d: 1.4–1.5 (m, 6,
(CH2)3), 2.47–2.51 (m, 4H, N(CH2)2), 2.71–2.76 (t, 2H,
NCH2), 4.30–4.36 (t, 2H, OCH2), 6.72–6.74 (d, 1H, H-
4), 6.79–6.85 (dd, 1H, H-2), 7.5 (s, 1H, H-7), 7.71 (s, 1H,
H-10), 8.18–8.23 (dd, 1H, H-2). Anal. Calcd for
C20H21NO5: C, 67.59; H, 5.96; N, 3.94. Found C, 67.61;
H, 6.01; N, 4.13.
4.1.5. 3,9-Dihydroxy-dibenzo[b,d]pyran-6-one (3e). Yield
66%, mp > 280 ꢁC; MS: m=z 228 (Mþ); 1H NMR
(DMSO-d6) d: 6.72–6.73 (d, 1H, H-4), 6.80–6.86 (dd,
2H, H-2 and H-8), 7.45 (s, 1H, H-10), 7.79–8.08 (m, 2H,
H-1 and H-7).
4.1.11. 3-Isopropyloxy-dibenzo[b,d]pyran-6-one (4a). To
a solution of 3a (228 mg; 1 mM) in dry acetone (60 mL)
was added anhydrous potassium carbonate (276 mg;
2 mM) and isopropyl bromide (0.19 mL; 2 mmol). The
reaction mixture was stirred and refluxed (70 ꢁC) for
24 h. After completion of the reaction, the flask was
cooled, and the contents were filtered and the residue
washed with acetone (5 mL · 3). The filtrate was con-
centrated and the crude product was chromatographed
over silica gel column eluting the pure compound with
ethyl acetate–hexane (2%), yield 295 mg (94.5%), mp
4.1.6. 3,8-Dihydroxy-dibenzo[b,d]pyran-6-one (3f). Yield
58%, mp > 300 ꢁC; MS: m=z 228 (Mþ); 1H NMR
(CDCl3) d: 6.95–6.96 (d, 1H, H-4), 7.01–7.06 (dd, 1H,
H-2), 7.52–7.57 (dd, 1H, H-9), 7.73–7.75 (d, 1H, H-7),
8.22–8.27 (d, 1H, H-1), 8.31–8.35 (d, 1H, H-10), 10.38
(s, 1H, 8-OH), 10.45 (s, 1H, 3-OH).
1
78 ꢁC; MS: m=z 254 (Mþ); H NMR (CDCl3) d: 1.38–
1.40 (d, 6H, (CH3)2), 4.52–4.58 (m, 1H, CH), 6.4–6.7 (d,
1H, H-4), 6.90–6.95 (dd, 1H, H-2), 7.46–7.54 (t, 1H, H-
8), 7.74–7.78 (t, 1H, H-9), 7.92–7.96 (d, 1H, H-7), 7.98–
8.02 (d, 1H, H-10), 8.34–8.38 (d, 1H, H-1). Anal. Calcd
for C16H14O3: C, 75.57; H, 5.55. Found C, 75.78; H,
5.70.
4.1.7. 3-Hydroxy-8-methoxy-9-(2-pyrrolidin-1-yl-eth-
oxy)-dibenzo[b,d]pyran-6-one (3g). Yield 48%, mp
1
196 ꢁC; MS: m=z 355 (Mþ); H NMR (CDCl3) d: 1.70–
1.80 (m, 4H, (CH2)2), 2.50–2.57 (m, 4H, N(CH2)2), 2.88–
3.08 (t, 2H, NCH2), 3.98 (s, 1H, OCH3), 4.30–4.36 (t,
2H, OCH2), 6.73–6.79 (d, 1H, H-4), 6.84–6.86 (dd, 1H,
H-2), 7.53 (s, 1H, H-7), 7.64 (s, 1H, H-10), 8.18–8.22 (s,
1H, H-1), 9.13 (s, 1H, OH).
4.1.12. 3-Isopropyloxy 8,9-dimethoxy-dibenzo[b,d]pyran-
6-one (4b). Yield 88.28%, mp 218 ꢁC; MS: m=z 314 (Mþ);
1H NMR (CDCl3) d: 1.38–1.40 (d, 6H, (CH3)2), 3.99 (s,
3H, OCH3), 4.07 (s, 3H, OCH3), 4.35–4.67 (m, 1H, CH),
6.8 (s, 1H, H-4), 6.90–6.95 (d,1H, H-2),7.32 (s, 1H, H-7),
7.77 (s, 1H, H-10), 7.79 (d, 1H, H-1). Anal. Calcd for
C18H18O5: C, 68.78; H, 5.77. Found C, 67.97; H, 5.85.
4.1.8. 3-Hydroxy-8-methoxy-9-(2-piperidin-1-yl-ethoxy)-
dibenzo[b,d]pyran-6-one (3h). Yield 50%, mp 205 ꢁC; MS:
m=z 369 (Mþ); 1H NMR (CDCl3) d: 1.4–1.5 (m, 6,
(CH2)3), 2.47–2.51 (m, 4H, N(CH2)2), 2.71–2.76 (t, 2H,
NCH2), 3.77 (s, 3H, OCH3), 4.30–4.36 (t, 2H, OCH2),
6.72–6.74 (d, 1H, H-4), 6.79–6.85 (dd, 1H, H-2), 7.5 (s,
1H, H-7), 7.71 (s, 1H, H-10), 8.18–8.23 (dd, 1H, H-2).
4.1.13. 3,9-Diisopropyloxy-8-methoxy-6H-dibenzo[b,d]-
pyran-6-one (4c). Yield 80%, mp 196 ꢁC, MS: m=z 342