A mixture of (-)-(1R,4S)-2-azabicyclo[2.2.1]hept-5-en-3-one 83 (3.0 g, 27.5 mmol) and 1.25 M HCl in MeOH (59.0 mL, 73.8 mmol) was heated and refluxed for 12 h. The mixture was concentrated under reduced pressure and the residue was stirred with Et2O (42 mL). The solid obtained was collected, washed with Et2O and dried in vacuo to give 4.2 g (85%) of (1S, 4R)-(-)-methyl-4-aminocyclopent-2-ene-1-carboxylate hydrochloride (84).
