[CH3:1][C:2]1[O:6][CH2:5][C:4](=[O:7])[CH:3]=1.[Cl-].[Ca+2].[Cl-].[OH:11][C:12]1[CH:19]=[C:18]([OH:20])[CH:17]=[CH:16][C:13]=1[CH:14]=O.B(OC(CC)C)(OC(CC)C)OC(CC)C>ClCCl.CN(C)C=O.C(N)CCC.C(O)(=O)C>[OH:11][C:12]1[CH:19]=[C:18]([OH:20])[CH:17]=[CH:16][C:13]=1[CH:14]=[C:5]1[C:4](=[O:7])[CH:3]=[C:2]([CH3:1])[O:6]15-methyl-furan-3-one (2, 5.9 g g, 0.060 mol) was dissolved in dichloromethane (80 mL) and taken in a 3-necked 500 mL round bottomed flask fitted with a mechanical agitator and calcium chloride guard tube. 2,4-Dihydroxybenzaldehyde (3d, 7.4 g, 0.053 mol) dissolved in dimethylformamide (8 mL) was added. The mixture was cooled to 0-5° C. with stirring. Tri-sec-butyl borate (13.4 g, 0.058 mol) was added and stirred for 2 h. n-Butyl amine (9 drops) was added over a period of 3 h and the reaction mixture allowed to warm to room temp. on its own and stirred at room temp. overnight. The dark red color solution was poured into 5% aq. acetic acid solution (120 mL) preheated to 60° C. with stirring. This was stirred for 30 min., and then allowed to settle down. The dichloromethane layer was isolated and concentrated under reduced pressure to get red color gummy material. This gummy material was washed with water (3×20 mL). Acetonitrile (20 mL) was added to the gummy material and stirred vigorously. The product precipitated out. This was filtered, washed with acetonitrile (20 mL), and the filtered solid dried in vacuo at 110° C., get pure 2-(2,4-Dihydroxy-benzylidene)-5-methyl-furan-3-one (4d) as a red powder (6.5 g, 50% yield), m.p. 239.4-242.5° C. (decomposes).
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