Sodium Hydroxide → HCID 58010220, Verbindung

A 250 mL round-bottomed flask was charged with ethyl 4-(tert-butoxycarbonylamino)-2-ethylcyclopentanecarboxylate (3.00 g, 10.5 mmol) in THF (96 mL) to give a colorless solution. An aqueous solution of NaOH (1 N, 16.0 mL, 16.0 mmol) was added and the reaction mixture was stirred for about 24 h at ambient temperature. Additional aqueous NaOH (1 N, 5.00 mL, 5.00 mmol) was added and stirring was continued for about 48 h at room temperature. The reaction mixture was heated to about 50° C. for about 24 h. The solvent was removed under reduced pressure. AcOH was added until pH 5 was reached. EtOAc (50 mL) was added and the layers were partitioned. The aqueous layer was further extracted with EtOAc (2×30 mL). The combined organic extracts were dried over anhydrous MgSO4, filtered, and concentrated under reduced pressure to give a yellow oil. The oil was further dried under high vacuum, resulting in formation of a solid that was dissolved in DCM and concentrated to dryness, re-suspended in DCM and re-concentrated to dryness. The residue was then suspended in Et2O and concentrated to dryness and further dried under vacuum for about 3 h to give 4-(tert-butoxycarbonylamino)-2-ethylcyclopentanecarboxylic acid (2.36 g, 87%): LC/MS (Table 2, Method a) Rt=2.09 min; MS m/z: 256 (M−H)−.