Provided is a process for preparing a compound of formula 1 or its salt. The process includes reacting a compound of formula 4 with acetaldehyde in a mixed solvent including water, isopropanol, and methylenechloride in a volume ratio of 1:3-6:11-14 in the presence of a first base to stereospecifically prepare a compound of formula 3 and reacting the compound of the formula 3 with an anhydrous compound of formula 2 in the presence of a second base.
提供了一种制备式1化合物或其盐的方法。该方法包括在包括
水、
异丙醇和
二氯甲烷的混合溶剂中,在第一碱存在下,将式4化合物与
乙醛反应,以立体选择性地制备式3化合物,并在第二碱存在下将式3化合物与无
水式2化合物反应。混合溶剂的体积比为1:3-6:11-14。