Methanol → HCID 21946122, compound

Reaction equation

[CH2:1]=[C:2]1O[C:4](=[O:5])[CH2:3]1.[Cl:7][C:8]1[C:9]([OH:21])=[C:10]([CH2:15][CH2:16][C:17]([O:19][CH3:20])=[O:18])[CH:11]=[CH:12][C:13]=1[OH:14].CO>CS(O)(=O)=O>[Cl:7][C:8]1[C:9]([OH:21])=[C:10]([CH2:15][CH2:16][C:17]([O:19][CH3:20])=[O:18])[CH:11]=[C:12]2[C:13]=1[O:14][C:4](=[O:5])[CH:3]=[C:2]2[CH3:1]

Participants

Procedure

Diketene (0.7 ml, 9.1 mmol) was added dropwise to a stirred solution of 5a (1.0 g, 4.3 mmol) in 7 ml of methanesulfonic acid. The resultant solution was heated at 70° C. for 5 min and cooled. Methanol (20 ml) was added and the reaction was heated to boiling; this treatment esterified small amount of free acid formed during the cyclization step. Methanol was evaporated and water was added to precipitate the product. The crude material was chromatographed on silica eluting with ethyl acetate. Concentration of the pure product fractions and drying under vacuum afforded 0.82 g (64%) of the desired product as a pale yellow solid. 1H NMR (DMSO-d6): δ 10.45 (s, 1H), 7.50 (s, 1H), 6.24 (s, 1H), 3.59 (s, 3H), 2.93 (t, J=7.5 Hz, 2H), 2.62 (t, J=7.5 Hz, 2H), 2.38 (s, 3H).