C[Si](Cl)(C)C.[OH:6][C:7]1([C:10]([OH:12])=O)[CH2:9][CH2:8]1.C(Cl)(=O)C(Cl)=O.[CH3:19][NH:20][CH3:21].C(O)(=O)CC(CC(O)=O)(C(O)=O)O>ClCCl.N1C=CC=CC=1.CN(C)C=O.CO>[OH:6][C:7]1([C:10]([N:20]([CH3:21])[CH3:19])=[O:12])[CH2:9][CH2:8]1
17.1 ml of trimethylsilyl chloride are added dropwise to a solution of 6 g of 1-hydroxy-cyclopropanecarboxylic acid in 120 ml of dichloromethane and 10.5 ml of pyridine. After stirring for 4 hours at ambient temperature, the mixture is cooled to 0° C., and 10 drops of dimethylformamide and then 5.4 ml of oxalyl chloride are added. The reaction mixture is stirred at 0° C. for 1 hour and at ambient temperature for 1 hour; a solution of 2.4 g of dimethylamine in 10 ml of pyridine is then added. Stirring is continued for 20 hours and then, after cooling to 0° C., 14 g of citric acid in 120 ml of methanol are added. After returning to ambient temperature for one hour, the reaction mixture is washed with 1N hydrochloric acid solution and then with NaHCO3-saturated solution and then NaCl-saturated solution. The organic phase is treated in conventional manner and chromatography over silica gel (dichloromethane/tetrahydrofuran: 90/10) allows the expected product to be isolated.
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