CC1(C)S(=O)(=[O:7])C2CC(=O)N2C1C([O-])=O.[Na+].[C:17]([O:28]CC1C=CC=CC=1)(=[O:27])[CH2:18][CH2:19][CH2:20][CH2:21][C:22]([O:24]CCl)=[O:23].O>[Br-].C([N+](CCCC)(CCCC)CCCC)CCC.C(OCC)(=O)C.CC(C)=O.[Pd]>[OH2:7].[C:17]([OH:28])(=[O:27])[CH2:18][CH2:19][CH2:20][CH2:21][C:22]([OH:24])=[O:23]To 400 ml acetone is added 48.5 g (0.19 mole) sodium 1,1-dioxopenicillanate, 48.0 g (0.17 mole) benzyl chloromethyl adipate and 19.3 g (0.06 mole) tetrabutylammonium bromide. The mixture is heated at reflux under nitrogen overnight, filtered, washed with acetone and the filtrate evaporated. The residue is taken up in 500 ml ethyl acetate, washed alternately with brine and water, 250 ml portions, brine again and dried (MgSO4). Evaporation of solvent in vacuo afforded 89.6 g light yellow oil. The oil is taken up in 250 ml ethyl acetate, 20.0 g 10% Pd/C added and the mixture is hydrogenated at 3.52 kg/cm2 for one hour. After adding 15 g of fresh catalyst the hydrogenation is continued for 2.5 hours. The catalyst is removed by filtration, the cake washed with acetone (1500 ml) and the combined filtrate and washings evaporated in vacuo to obtain a viscous oil. The oil is taken up in 150 ml acetone and water added slowly to start crystallization, then continued until 800 ml water is added. After stirring 30 minutes, the crystalline product is recovered by filtration, washing with water and air dried to obtain 58.2 g of the title carboxylic acid. Recrystallization from ethyl acetate affords the crystalline monohydrate, m.p. 100°-102° C.
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