Ethyl 4-[4-methoxy-4-(methoxycarbonyl)piperidin-1-yl]azepane-1-carboxylate (0.136 g, 0.39 mmol) was dissolved in THF (5 mL) at rt and 1M LiOH sol. (0.4 mL) was added. The reaction mixture was stirred at rt for 2 days. The pH was carefully adjusted to pH 6 by addition of concentrated hydrochloric acid, the solvents were removed in vacuo, to give 1-[1-(ethoxycarbonyl)azepan-4-yl]-4-methoxypiperidine-4-carboxylic acid (0.131 g), Intermediate 8, as a yellow oil which was used directly without further purification.
