The object of the present invention is to provide 1-(1-tert- butoxycarbonyl-4-piperidylacetyl)-4- mesyloxypiperidine having a low content of impurities
The object can be solved by a method for preparing 1-(1-benzyl-4-piperidylacetyl)-4-hydroxypiperidine, comprising the steps of:
(1) reductively reacting 1-benzyl-4-piperidylidene acetic acid ethyl ester represented by the formula [1]:
to obtain 1-benzyl-4-piperidyl acetic acid ethyl ester represented by the formula [2]:
 (2) adding an ammonium chloride aqueous solution and an organic solvent to the liquid containing 1-benzyl-4-piperidyl acetic acid ethyl ester, mixing the whole, and separating into an organic layer and an aqueous layer, (3) collecting 1-benzyl-4-piperidyl acetic acid ethyl ester from the organic layer, and (4) reacting the obtained 1-benzyl-4-piperidyl acetic acid ethyl ester with 4-hydroxypiperidine represented by the formula [3]:
in the presence of base, to obtain 1-(1-benzyl-4-piperidylacetyl)-4-hydroxypiperidine represented by the formula [4]:
                            本发明的目的是提供杂质含量低的 1-(1-叔丁氧羰基-4-
哌啶乙酰基)-
4-甲氧基哌啶。
本发明的目的可以通过制备1-(1-苄基-4-
哌啶乙酰基)-
4-甲氧基哌啶的方法来解决,该方法包括以下步骤:
(1) 将式[1]代表的 
1-苄基-4-哌啶乙酸乙酯进行还原反应:
得到式[2]代表的 
1-苄基-4-哌啶乙酸乙酯:
 (2) 向含有 1-苄基-4-
哌啶基乙酸乙酯的液体中加入
氯化铵水溶液和有机溶剂,混合,分离成有机层和
水层,(3) 从有机层中收集 1-苄基-4-
哌啶基乙酸乙酯,(4) 将得到的 1-苄基-4-
哌啶基乙酸乙酯与式[3]代表的 
4-羟基哌啶反应:
在碱存在下,得到式[4]代表的 1-(1-苄基-4-
哌啶乙酰基)-
4-羟基哌啶: