(7R)-benzyl 2,4-dioxo-1,3-diazaspiro[4.4]nonane-7-carboxylate → (7R)-2,4-dioxo-1,3-diazaspiro[4.4]nonane-7-carboxylic acid

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Reaction Steps

To (7R)-benzyl 2,4-dioxo-1,3-diazaspiro[4.4]nonane-7-carboxylate (from step A, 0.14 g, 0.486 mmol) in methanol (10 mL) was added Pd—C (0.030 g, 0.282 mmol) under a nitrogen atmosphere. The contents were hydrogenated at 10 psi for 3 hours. The reaction mixture was filtered over a whatman filter (FN MB 25 MM 0.45 uM) paper and washed with methanol (2×5 mL). The filtrate was concentrated under reduced pressure to yield a solid (0.09 g, 0.454 mmol, 94% yield). It was used as such for the subsequent step without further purification. MS m/z 197.3 (M−H)+

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