M. Dixit et al. / Bioorg. Med. Chem. 15 (2007) 727–734
731
3. Experimental
NMR (200 MHz, CDCl3): d 2.69 (s, 3H, CH3), 2.82 (s,
3H, CH3), 4.80–4.88 (m, 2H, CH2), 4.97–5.02 (m, 1H,
CH), 6.44 (s, 1H, CH), 6.52 (d, 1H, J = 8.4 Hz, ArH),
6.88 (d, 1H, J = 8.6 Hz, ArH), 7.30 (d, 1H, J = 8.4 Hz,
ArH), 7.56 (d, 1H, J = 8.6 Hz, ArH), 12.74 (s, 1H,
OH), 12.81 (s, 1H, OH); 13C NMR (50.32 MHz,
CDCl3): d 31.6 (CH3), 32.0 (CH3), 41.1 (CH), 77.2
(CH2), 103.5 (@CH), 107.3, 107.5, 110.3, 114.5, 117.2,
120.5, 128.5, 131.9, 154.2, 156.5, 161.8, 161.9, 164.0,
202.3, 203.5; HRMS calcd for C20H16O6 352.0947,
found 352.0941.
3.1. Chemistry
All the chemicals and reagents used were of analytical
grade and were purchased from Sigma–Aldrich Chem-
ical Co. H NMR and 13C NMR spectra were taken
1
on a Bruker WM-200, Bruker WM-300, at 200 and
300 MHz, respectively. CDCl3 was taken as the sol-
vent. Chemical shifts are reported in parts per million
shift (d value) from Me4Si (d 0 ppm for 1H) or based
on the middle peak of the solvent (CDCl3) (d
77.00 ppm for 13C NMR) as an internal standard. Sig-
nal patterns are indicated as s, singlet; d, doublet; dd,
double doublet; t, triplet; m, multiplet. Coupling con-
stant (J) are given in hertz. Infrared (IR) spectra were
recorded on a Perkin-Elmer AX-1 spectrophotometer
in KBr disc and reported in wave number (cmꢁ1).
Fast-atomic bombardment (FAB) spectrometer was
used for mass spectra analysis. Melting points were
measured with Buchi-530 melting point apparatus.
All the reactions were carried out under anhydrous
conditions and were monitored by TLC; visualization
was done with UV-light (254 nm).
3.1.1.4.
1-(4-Acetyl-5,50-dihydroxy-20,30-dihydro-
[2,30]bibenzofuranyl-40-yl)-ethanone (21). Yellow semi-
solid; yield: 83%; MS (FAB): m/z = 353 (M++1); IR
(KBr): 1645 (CO), 3437 cmꢁ1 (OH); 1H NMR
(200 MHz, CDCl3): d 2.50 (s, 3H, CH3), 2.57 (s, 3H,
CH3), 4.73–4.88 (m, 3H, CH and CH2), 6.41 (d, 1H,
J = 8.6 Hz, ArH), 6.61 (s, 1H, CH), 6.95 (d, 1H,
J = 8.6 Hz, ArH), 7.50–7.66 (m, 2H, ArH), 12.76 (s,
1H, OH), 13.08 (s, 1H, OH).
3.1.1.5.
1-(60-Acetyl-5,50-dihydroxy-20,30-dihydro-
[2,30]bibenzofuranyl-6-yl)-ethanone (22). Yellow solid;
yield: 75%; mp: 192–193 ꢁC; MS (FAB): m/z = 353
(M++1); IR (KBr): 1648 (CO), 3422 cmꢁ1 (OH); 1H
NMR (200 MHz, CDCl3): d 2.53 (s, 3H, CH3), 2.68 (s,
3H, CH3), 4.75–4.80 (m, 2H, CH2), 4.82–4.99 (m, 1H,
CH), 6.43 (s, 1H, ArH), 6.46 (s, 1H, CH), 6.99 (s, 1H,
ArH), 7.58 (s, 1H, ArH), 7.91 (s, 1H, ArH), 12.47 (s,
1H, OH), 13.03 (s, 1H, OH); HRMS calcd for
C20H16O6 352.0947, found 352.0987.
3.1.1. General procedure for synthesis of 20,30-dihydro-
[2,30]bibenzofuran (5, 6, 17a, 21, 22, and 24). The benzo-
furan (3, 4, 16, 19, 20, or 23) was refluxed in toluene
(35 mL) with A 15 (0.22 g) at 120 ꢁC for 6–10 h. The
resulting reaction mixture was filtered and the resin
was washed with excess of toluene. The filtrate thus ob-
tained was concentrated to dryness and a pure com-
pound was isolated by silica gel column
chromatography using 7% EtOAc in hexane as eluent.
3.1.1.6. 4,40-Dihydroxy-20,30-dihydro-[2,30]bibenzof-
uranyl-5,50-dicarboxylic acid dimethyl ester (24). Yellow
solid; yield: 86%; mp: 184–185 ꢁC; MS (FAB): m/
z = 385 (M++1); IR (KBr): 1678 (CO), 3426 cmꢁ1
(OH); 1H NMR (200 MHz, CDCl3): d 3.91 (s, 3H,
OCH3), 3.95 (s, 3H, OCH3), 4.78–4.95 (m, 3H, CH
and CH2), 6.65 (s, 1H, CH), 6.47 (d, 1H, J = 8.6 Hz,
ArH), 6.96 (d, 1H, J = 8.8 Hz, ArH), 7.72 (d, 1H,
J = 8.8 Hz, ArH), 7.81 (d, 1H, J = 8.6 Hz, ArH), 12.42
(s, 1H, OH), 13.01 (s, 1H, OH); HRMS calcd for
C20H16O8 384.0845, found 384.0870.
3.1.1.1.
1-(5-Acetyl-4,40-dihydroxy-20,30-dihydro-
[2,30]bibenzofuranyl-50-yl)-ethanone (5). Yellow solid;
yield: 81%; mp: 189–190 ꢁC; MS (FAB): m/z 353
(M++1); IR (KBr): 1641 (CO), 3427 cmꢁ1 (OH);
1H NMR (200 MHz, CDCl3): d 2.53 (s, 3H, CH3),
2.68 (s, 3H, CH3), 4.75–4.80 (m, 2H, CH2),
4.92–4.96 (m, 1H, CH), 6.43 (s, 1H, ArH), 6.46 (s,
1H, CH), 6.99 (s, 1H, ArH), 7.58 (s, 1H, ArH),
7.91 (s, 1H, ArH), 12.46 (s, 1H, OH), 13.02 (s,
1H, OH); HRMS calcd for C20H16O6 352.0947,
found 352.0918.
3.1.2. Procedure for the synthesis of compound 1-(5-
acetyl-6,60-dimethoxy-20,30-dihydro-[2,30]bibenzofuranyl-
50-yl)-ethanone (17b). The mixture of 17a with methyl
iodide in the presence of K2CO3 in acetone was re-
fluxed for 5 h and after completion of reaction; reac-
tion mixture was filtered and evaporated under
vacuum to yield the compound 17b as colorless oil
in good yield.
3.1.1.2.
1-(5-Acetyl-6,60-dihydroxy-20,30-dihydro-
[2,30]-bibenzofuranyl-50-yl)-ethanone (6). Yellow solid;
yield: 89%; mp: 149–150 ꢁC; MS (FAB): m/z 353
(M++1); IR (KBr): 1638 (CO), 3433 cmꢁ1 (OH); 1H
NMR (200 MHz, CDCl3): d 2.57 (s, 3H, CH3), 2.64 (s,
3H, CH3), 4.81–4.88 (m, 1H, CH), 4.89–4.94 (m, 2H,
CH2), 6.48 (d, 1H, J = 8.6 Hz, ArH), 6.68 (s, 1H, CH),
6.96 (d, 1H, J = 8.8 Hz, ArH), 7.60 (d, 1H, J = 8.8 Hz,
ArH), 7.70 (d, 1H, J = 8.6 Hz, ArH), 12.83 (s, 1H,
OH), 13.15 (s, 1H, OH); HRMS calcd for C20H16O6
352.0947, found 352.0946.
Yield: 95%; colorless oil; MS (FAB): m/z 381 (M++1);
IR (KBr): 1637 (CO) cmꢁ1 1H NMR (200 MHz,
;
CDCl3): d 2.57 (s, 3H, CH3), 2.68 (s, 3H, CH3), 3.85
(s, 3H, OCH3), 3.92 (s, 3H, OCH3), 4.73–4.86 (m, 2H,
CH2), 4.93–4.97 (m, 1H, CH), 6.34 (s, 1H, CH), 6.48
(d, 1H, J = 8.4 Hz, ArH), 6.90 (d, 1H, J = 8.6 Hz,
ArH), 7.29 (d, 1H, J = 8.4 Hz, ArH), 7.48 (d, 1H,
J = 8.6 Hz, ArH); HRMS calcd for C22H20O6
380.1260, found 380.1274.
3.1.1.3.
1-(70-Acetyl-6,60-dihydroxy-20,30-dihydro-
[2,30]bibenzofuranyl-7-yl)-ethanone (17a). Yellow solid;
yield: 92%; mp: 110–111 ꢁC; MS (FAB): m/z 353
(M++1); IR (KBr): 1637 (CO), 3449 cmꢁ1 (OH); 1H