R-(+)-2-(4-羟基苯氧基)丙酸的不对称合成

Asymmetrical synthesis of R-(+)-2-(4-Hydroxyphenoxy) propionic acid

以具光活性的L-乳酸为起始原料,经酯化、磺酰化及醚化三步反应,醚化反应中发生构型反转,最终得到R-(+)-2-(4-羟基苯氧基)丙酸.在磺酰化反应中,以三乙胺作缚酸剂,TEBAC为催化剂,投料比为n(L-乳酸乙酯)∶n(对甲苯磺酰氯)∶n(三乙胺)=1∶1∶1.2,反应温度为0℃,反应时间为5 h,中间体S-(-)-2-(4-甲苯磺酰氧基)丙酸乙酯质量分数为98.0%,收率为96.5%.在醚化反应中,氮气氛下,以水作溶剂,投料比为n(对苯二酚)∶n(S-(-)-2-(4-甲苯磺酰氧基)丙酸乙酯)=1.2∶1,反应温度为30℃,反应时间为6 h,产物R-(+)-2-(4-羟基苯氧基)丙酸的质量分数为99.5%,收率为72.4%(以L-乳酸计),光学纯度97.9%.产物结构经1H NMR,IR和MS表征确认.

Using optical L-lactic acid as the starting material, R-（＋）-2-（4-hydroxyphenoxy） propionic acid was synthesized via esterification, sulfonylation and etherification reaction, and the configuration was reversed in etherification reaction. In sulfonylation reaction, using Et3N as a base and TEBAC as a catalyst, the molar ratio of L-ethyl lactate to p-toluenesulfonyl chloride to Et3N was 1 ： 1 ： 1.2, reaction temperature 0 ℃, reaction time 5 h, the yield of ethyl S-（-）-2-（4- toluenesulfonyloxy）lactate was 96. 5% with the purity of 98. 0%; In etherifieation reaction, using H20 as a solvent in N2. atmosphere, the molar ratio of hydroquinone to ethyl S-（-）-2-（4- toluenesulfonyloxy）lactate was 1.2 ： 1, reaction temperature 30 ℃, reaction time 6 h, under the optimum conditions, the yield of R-（＋）-2-（4-hydroxyphenoxy）propionic acid was 72.4% based on L-lactic acid with the purity of 99.5 %, and the optical purity was confirmed to he 97.9 %. The structure of R-（＋）-2-（4-hydroxyphenoxy）propionic acid was confirmed by ^1H NMR, IR and MS.