C(NC(C)C)(C)C.C([Li])CCC.[C:13]([O:16][CH2:17][CH3:18])(=[O:15])[CH3:14].[C:19]1(=[CH:22][C:23]([O:25][CH3:26])=[O:24])[CH2:21][CH2:20]1.[Cl-].[NH4+]>CCCCCC.C1COCC1>[C:19]1([CH2:14][C:13]([O:16][CH2:17][CH3:18])=[O:15])([CH2:22][C:23]([O:25][CH3:26])=[O:24])[CH2:21][CH2:20]1
240 ml (1.70 mol) of diisopropylamine were dissolved in 700 ml of abs. THF, the mixture was cooled to −40° C. and 681 ml (1.7 mol) of a 2.5 M solution of n-butyllithium in hexane were added slowly. The solution was stirred at −40° C. for 30 min and then cooled to −78° C., and a solution of 166.6 ml (1.7 mol) of ethyl acetate p.a. in 200 ml of abs. THF was added. After the end of the addition, the mixture was stirred at −78° C. for another 30 min 159 g (crude product, about 1.42 mol) of methyl cyclopropylideneacetate, dissolved in a little abs. THF, were then added dropwise. The reaction mixture was stirred at −78° C. for 1 h and then, via −40° C., slowly warmed to about 0° C., and a saturated aqueous ammonium chloride solution was finally added. The mixture was extracted with ethyl acetate and the organic phase was washed with 1 N hydrochloric acid and sat. sodium chloride solution, dried over sodium sulphate and concentrated under reduced pressure. The residue was purified chromatographically on silica gel (mobile phase cyclohexane/ethyl acetate 9:1). This gave 109.5 g of the target compound which was contaminated by the diethyl ester derivative and was not purified any further.
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