Pentanoic acid, 2-acetyl-, ethyl ester → 7-Hydroxy-4-methyl-3-propyl-2H-chromen-2-one
Reaktionsgleichung
[CH2:1]([CH:4]([C:10]([CH3:12])=O)[C:5]([O:7][CH2:8][CH3:9])=[O:6])[CH2:2][CH3:3].[CH:13](Cl)(Cl)Cl.[CH3:17][C:18]([CH3:20])=[O:19]>>[OH:19][C:18]1[CH:20]=[C:8]2[C:9]([C:10]([CH3:12])=[C:4]([CH2:1][CH2:2][CH3:3])[C:5](=[O:6])[O:7]2)=[CH:13][CH:17]=1Komponenten
3
Versuchsvorschrift
This was prepared from 9 (1.72 g) in a similar manner to the preparation of 3. The yellow/brown crude product that obtained was fractionated by flash chromatography (chloroform/acetone, 20:1 to 1:1 gradient). The product that isolated was further purified by recrystallisation from ethyl acetate/hexane (2:3) to give 10 as creamy crystals (813 mg, 3.73 mmol, ca. 37%); mp 160-173° C. [Lit. [73] 171-173° C. (aq. ethanol)]; δH (400 MHz, DMSO-d6) 0.92 (3H, t, J=7.3 Hz, CH3), 1.45 (2H, sextet, J=7.5 Hz, —CH2CH2CH3), 2.36 (3H, s, C4-CH3), 2.51 (2H, t, J=7.7 Hz, —CH2CH2CH3), 6.67 (1H, d, J=2.4 Hz, C8-H), 6.79 (1H, dd, J=2.4 and 8.4 Hz, C6-H), 7.60 (1H, d, J=8.8 Hz, C5-H) and 10.38 (1H, br s, exchanged with D2O, OH); MS (FAB+) m/z (rel. intensity) 437.2[10, (2M+H)+], 219.2[100, (M+H)+]; MS (FAB−) m/z (rel. intensity) 435.2[12, (2M−H)−], 371.1[15, (M+NBA)−], 217.1[100, (M−H)−]; HRMS (FAB+) m/z 219.10300 [(M+H)+], calcd for C13H15O3 219.10212. Found: C, 71.7; H, 6.49; C13H14O3 requires C, 71.53; H, 6.47%.