Lactams. XXVI. Regioselectivity in the mercuric acetate-edetic acid oxidation of the ethyl 1-(2-aryl-2-hydroxyethyl)-3-ethyl-4-piperidineacetate system: Enhancement by a benzyloxy group in the aryl moiety and by the 3,4-cis configuration.
作者:TOZO FUJII、MASASHI OHBA、MICHIKO TSUCHIDA、KIYOE SAITO、YUKO HIRANO、JUN SAKAGUCHI
DOI:10.1248/cpb.34.496
日期:——
A quantitative analytical study to determine the isomer ratios of the 6-piperidones (type 7) and 2-piperidones (type 5) produced by the mercuric acetate-edetic acid (EDTA) oxidation of 1-(2-aryl-2-hydroxyethyl)-3-alkylpiperidines (±)-4c, d, f, h, 4e, g, i, j, and (±)-38 was carried out. It has been found that all the substrates with a benzyloxy group in the aryl moiety, regardless of its location, undergo oxidation at the 6-position preferentially as compared with the debenzyloxy derivatives such as (±)-4a, b. Comparison of the quantitative data from 4e and (±)-4f with those from (±)-4b indicated that the cis acetate chain at the 4-position increases the extent of the 6-oxidation, whereas a trans acetate chain at the same position has little effect. These two factors enhance the practical value of the "cincholoipon-incorporating method" for chiral syntheses of the 1-type Alangium alkaloids, in which the mercuric acetate-EDTA oxidation of 4e, g, i, j to the 6-piperidones (type 3)is one of the key synthetic operations.
进行了一项定量分析研究,以确定由醋酸汞-乙二胺四乙酸(EDTA)氧化1-(2-芳基-2-羟基乙基)-3-烷基哌啶(±)-4c、d、f、h、4e、g、i、j和(±)-38生成的6-哌啶酮(类型7)和2-哌啶酮(类型5)的异构比。研究发现,所有具有苄氧基团的芳基底物,无论其位置如何,与去苄氧基衍生物(如±-4a、b)相比,更倾向于在6位发生氧化。将4e和(±)-4f的定量数据与(±)-4b的数据进行比较表明,4位的顺式乙酸链增加了6位氧化的程度,而同一位置的反式乙酸链则几乎没有影响。这两个因素增强了“金鸡纳碱引入法”在手性合成1类阿兰基麻黄碱中的实际应用价值,其中4e、g、i、j的醋酸汞-EDTA氧化生成6-哌啶酮(类型3)是关键的合成操作之一。