The procedures can be divided to the direct and indirect methods depending on whether the ( s ) - 2 - aminobutanol intermediate be involved : the former is to obtain the chiral ethambutol directly ; the latter is to get the ( s ) - 2 - aminobutanol intermediate firstly and the final product is synthesized through n - alkyl reactions 直接法就是直接合成得到手性的乙胺丁醇；间接法是先合成乙胺丁醇的关键中间体( s ) - 2 -氨基丁醇，再通过n -烷基化反应得到最终产品。
