Acetic Acid → 1-[3-((S)-4-hydroxy-6-aza-spiro[2,5]oct-6-yl)-propyl]-3-methyl-piperazin-2-one dihydrochloride

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Reaction Steps

To a suspension of (S)-6-aza-spiro[2.5]octan-4-ol hydrochloride (intermediate 25; 0.03 g, 0.2 mmol) in dichloromethane (1 ml) was added triethylamine (0.03 ml, 0.2 mmol) and acetic acid (0.02 ml, 0.4 mmol) followed by a solution of crude 2-methyl-3-oxo-4-(3-oxo-propyl)-piperazine-1-carboxylic acid tert-butyl ester (intermediate 14c; 0.06 g, 0.24 mmol) in dichloromethane (1 ml). Sodium triacetoxyborohydride (0.06 g, 0.26 mmol) was then added and the mixture stirred for 2 h, after which time the mixture was washed with saturated aq. sodium hydrogencarbonate solution, dried (Na2SO4) and concentrated. The crude residue was then treated with HCl in dioxane (2 ml, 4 N) and stirred for 30 minutes after which time the reaction was concentrated to afford crude 1-[3-((S)-4-hydroxy-6-aza-spiro[2.5]oct-6-yl)-propyl]-3-methyl-piperazin-2-one dihydrochloride as a white powder (0.1 g). To a solution of crude 1-[3-((S)-4-hydroxy-6-aza-spiro[2.5]oct-6-yl)-propyl]-3-methyl-piperazin-2-one dihydrochloride (0.03 g, 0.1 mmol) in N,N-dimethylformamide (0.8 ml) was added 3,4-dichlorocinnamic acid (0.2 g, 0.1 mmol), triethylamine (0.05 ml, 0.4 mmol) and O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluoro-phosphate (4 g, 0.1 mmol) and the reaction shaken for 1 h, after which time the reaction mixture was directly purified by preparative HPLC. This afforded the titled product as a colorless gum. MS (ISP)=480.1 (M+H)+.

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