Water → 2-Cyclopenten-1-one, 4-hydroxy-3-methyl-2-(2-propenyl)-, (S)-
Reaction equation
[OH2:1].[C:2]1([CH3:12])[CH:7]=[CH:6][C:5](S(O)(=O)=O)=[CH:4][CH:3]=1.[OH2:13].O1CCO[CH2:16][CH2:15]1>>[CH3:15][C:16]1[C@@H:12]([OH:13])[CH2:2][C:7](=[O:1])[C:6]=1[CH2:5][CH:4]=[CH2:3]Participants
4
Procedure
A mixture of 2.7 g of (3R, 3aR, 4S, 7R, 7aS) 3-[(1S)-2-methyl-4-oxo-3-(2-propen-1-yl)-cyclopent-2-enyloxy]-tetrahydro-4,7-methano-isobenzofuran-1-one, 0.25 g of p-toluene sulfonic acid monohydrate, 30 ml of water and 20 ml of dioxane was refluxed for 24 hours and then the solvent was evaporated under reduced pressure. The mixture was neutralized with triethylamine to a pH of 7 and was then evaporated to dryness under reduced pressure. The 2.8 g of residue was chromatographed over silica gel and was eluted with a 1-1 benzene-ethyl acetate mixture containing 0.1% of triethylamine to obtain 1 g of (S) allethrolone, 0.4 g of lactone and 0.7 g of a mixture of (S) allethrolone-lactone. The (S) allethrolone had a specific rotation of [α]D20 =+6.5°±1° (c=1.5% in benzene).