[CH3:1][C:2]1([CH3:13])[C@H:4]([CH:5]=[C:6]2[CH2:9][CH2:8][CH2:7]2)[C@H:3]1[C:10](Cl)=[O:11].[CH2:14]([OH:16])[CH3:15]>>[CH3:1][C:2]1([CH3:13])[C@H:4]([CH:5]=[C:6]2[CH2:9][CH2:8][CH2:7]2)[C@H:3]1[C:10]([O:16][CH2:14][CH3:15])=[O:11]A solution of 12 g of (1R,trans) 2,2-dimethyl-3-cyclobutylidenemethyl-cyclopropane-1-carboxylic acid chloride and 25 ml of ethanol was stirred at room temperature for 8 hours and was evaporated to dryness at 45° C. under reduced pressure. The residue was taken up in isopropyl ether and the solution was washed with water, dried and evaporated to dryness under reduced pressure at 45° C. The residue was chromatographed over silica gel and was eluted with a 9-1 petroleum ether (b.p.=60°-80° C.)--isopropyl ether mixture. The fraction with an Rf=0.35 was evaporated to dryness under reduced pressure at 45° C. and the product was rectified to obtain 8 g of ethyl (1R,trans) 2,2-dimethyl-3-cyclobutylidenemethyl-cyclopropane-1-carboxylate with a boiling point of 78°-79° C. at 0.1 mm Hg and a specific rotation of [α]D20 =-18° (c=2% in chloroform).
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