Keeping in view its importance, it was treated with DMSO-acetic anhydride an effective reagent which brings about a range of mechanistically interesting transformations in 4-hydroxycoumarin, dicoumarol,1 4-acyloxycoumarins2 and 3-substituted 4-hydroxycounmarins.3 In continuation with this, we now report structures of the compounds obtained from interaction of substituted dicoumarols (la–le) with this reagent and mechanism of their formation. A mixture of DMSO (6 ml), acetic anhydride (3 ml) and 3-3′-phenylmethylene-bis-4-hydroxycoumarin (200 mg) was kept at room temperature for 3 days.

Dilution with water afforded a precipitate which was filtered, washed and dried. Crystallization from benzene gave spiran (3). Data. Spiran (3): as needles (110 mg), m.p. 262–65 °C. IR (KBr): 1790, 1720, 1660 and 1600 cm−11H NMR (CDCI3, 90 MHz): δ 4.73 (lH,s,Ph–CH–); m/z 410 (M+) 333, 263, 262, 249, 205, 121 and 120 (Found C, 72.94; H, 3.56%. C25H14O6 Entinostat required C, 73.17; H, 3.41%). 3,3′-phenylmethylene-bis-4-hydroxycoumarin (2.4 g) dissolved in 30 ml DMSO-acetic anhydride mixture (2:1, v/v) Cabozantinib datasheet was kept on boiling water bath. A yellow crystalline material starts separating after 30 min. After heating for about 6 h the solid was filtered, washed with dry benzene and was found to be pure enough for

spectral studies. It was characterized as 7-phenyl-7H-bis [1] benzopyrano [4,3-b: 3′, 4′-c] pyran-6, 8-dione (4a). The filtrate was poured into water, precipitate filtered, washed and dried. Crystallization from benzene gave 2, 3-dihydro-2- (2-hydroxybenzoyl)-3-phenyl-4H-furo [3,2-c] [1] benzopyran-4-one (6) as white prisms (579 mg), m.p 199–212 °C. Identity of this compound was confirmed through direct comparison (mmp and comparison of spectral data) with the authentic

sample obtained earlier.4 Chromatography of the mother liquor gave further 500 mg of (6) (combined yield 1.079 g), 2,3-dihydro-2-hydroxymethyl-2- (α-2-hydroxybenzoyl)-3-α-phenyl-4H-furo [3,2-c] [I] benzopyran-4-one (7) as gummy mass (500 mg) and 2,3-dihydro-2-hydroxymelhyl-2- (α-2-hydroxybenzoyl)-3-β-phenyl-4H-furo [3,2-c] [1] benzopyran-4-one (8) also Dipeptidyl peptidase as a gummy mass (390 mg). Data. 7-phenyl-7H-bis [1] benzopyrano [4,3-b: 3', 4'-c] pyran-6, 8-dione (4a): (300 mg), m.p 312–20 °C (decomposition). IR (KBr) 1720, 1655 and 1600 cm−1. 1H NMR (FT, CDCI3, 90 MHz): δ 5.17 (lHs Ph–CH-); m/z 394 (M+) 317, 173, 145, 121 and 120. 2,3-dihydro-2-hydroxymethyl-2- (α-2-hydroxybenzoyl)-3-α-phenyl-4H-furo [3,2-c] [I] benzopyran-4-one (7): IR (KBr) 3300, 1720 (broad) 1620 cm−11H NMR (CDCl3, 100 MHz): δ 5.35 (1H, s, Ph–CH–), 4.05 (2H, d, -CH2–OH, J = 11.4 Hz). m/z 414 (M+ missing), 396, 384, 279, 263, 251, 250, 249, 222 and 221. 2,3-dihydro-2-hydroxymelhyl-2- (α-2-hydroxybenzoyl)-3-β-phenyl-4H-furo [3,2-c] [1] benzopyran-4-one (8): IR (KBr) 3300, 1720, and 1620 cm−1; 1H NMR (CDCl3, 100 MHz): δ 4.8 (1H, s, Ph–CH–), 4.