Synthesis
A solution of 3 g (42 mmol) of 3-buten-1-ol in 10 mL of anhydrous pyridine was cooled in an ice bath. Toluenesulfonyl chloride (7.9 g, 42 mmol) was added. After stirring for 3 hours, the mixture was poured into 30 mL of ice/concentrated HCl4/1v/v solution, extracted with 60 mL of ether and dried overnight in the refrigerator with MgSO4. The mixture was filtered, the ether was evaporated and 1.56 g (6.9 mmol) of ethyl acetamidodipropionate was dissolved in 10 mL of anhydrous THF under N2 at room temperature. Potassium tert-butoxide (0.80 g, 7 mmol) was added with vigorous stirring. The mixture was heated at 60??C for 2 hours. 3-Buten-1-ol 4-methylbenzenesulfonate (1.5 g, 6.9 mmol) was added and the mixture was heated to reflux for 2 days. THF was removed, the residue was quenched with 10 mL of 1MHCl and the crude product was extracted with ethyl acetate (25 mL). The ethyl acetate solution was washed twice with 25 mL of water, dried over MgSO4, filtered and concentrated. The crude product was purified by column chromatography (eluent cyclohexane/ethyl acetate 2/1v/v). The diethyl ester obtained as described above was hydrolyzed to a dicarboxylate by heating at reflux for 4 h in 25 mL of 10 w% NaOH. The solution was neutralized with 6MHCl and the solvent was evaporated. The diacid was extracted with 25mL of methanol. After evaporation of the solvent, 20 mL of 1MHCl was added and the solution was refluxed for 3 hours. The solvent was evaporated and the product was dissolved in 10mL of methanol. Propylene oxide (5 mL) was added and the mixture was stirred overnight at room temperature. The precipitate was filtered and 2-aminoheptanoic acid was dried.
