Methyl trans-4-((tert-Butoxycarbonyl)amino)-3-hydroxycyclopent-1-enecarboxylate (18). To a stirred solution of 17 (1.0 g, 4.44 mmol) in MeOH (30 mL) was added K2CO3 (1.84 g, 13.3 mmol). The resulting mixture was stirred at room temperature for 1 h. After the completion of the ...