C([Li])CCC.C(NC(C)C)(C)C.[O:13]1[C:18]2[CH:19]=[CH:20][CH:21]=[CH:22][C:17]=2[O:16][CH:15]=[C:14]1[C:23]([OH:25])=[O:24].[C:26](=[O:28])=[O:27]>CCCCCC.C1COCC1>[O:13]1[C:18]2[CH:19]=[CH:20][CH:21]=[CH:22][C:17]=2[O:16][C:15]([C:26]([OH:28])=[O:27])=[C:14]1[C:23]([OH:25])=[O:24]n-Butyl lithium (185 ml, of a 1.42M solution in hexane) was added to a solution of diisopropylamine (37.0 ml), in dry THF (300 ml) at -78° and the the solution was stirred for 0.25 h. A solution of 1,4-benzodioxin-2-carboxylic acid (23.40 g) in dry THF (400 ml) was then added over 0.5 h and the resulting solution was stirred at -78° for 1 h. The solution was then poured onto finely crushed CO2 and the mixture left to stand overnight. The mixture was evaporated and 2N-hydrochloric acid (250 ml) was added cautiously, followed by concentrated hydrochloric acid (40 ml). EA (500 ml) and THF (100 ml) were added to the mixture, which was shaken and the organic layer separated. The aqueous phase was further extracted with EA and the combined extracts were dried. Evaporation of the solvent gave an orange solid which was triturated under ER for 0.5 h. The solid was collected, washed with ER and dried in vacuo to afford the title compound (25.0 g) m.p. 215°-218°.
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