tert-Butyl [1-(aminocarbonothioyl)piperidin-4-yl]carbamate (Intermediate 125, 400 mg) was dissolved in anhydrous EtOH (5 ml). Ethyl 2-chloro-4-(2-methoxyethoxy)-3-oxobutanoate (Intermediate 124, 368 mg) was added and the mixture was heated at 90° C. for 18 h. Partial removal of Boc group was detected. Solvent was removed in vacuo and the dried material was treated with 4 N HCl/dioxane for 2 h. Solvent was removed in vacuo to give a brown/yellow solid which was dried to afford the title compound which was used without further purification (508 mg).
