Highly Chemoselective Esterification Reactions and Boc/THP/TBDMS Discriminating Deprotections under Samarium(III) Catalysis
摘要:
The usefulness of SmCl(3) as an excellent catalyst for chemoselective esterifications and selective removal of acid sensitive protecting groups such as Boc, THP, and TBDMS in the presence of one another is demonstrated through suitable examples.
The usefulness of SmCl(3) as an excellent catalyst for chemoselective esterifications and selective removal of acid sensitive protecting groups such as Boc, THP, and TBDMS in the presence of one another is demonstrated through suitable examples.
Efficient access to both enantiomers of 3-(1-hydroxyethyl)phenol by regioselective and enantioselective <i>CAL-B</i>
-catalyzed hydrolysis of diacetate in organic media by sodium carbonate
ol with vinyl acetate was also examined. Alkaline hydrolysis gave the best results, while good regioselectivity and enantioselectivity were observed in alcoholysis and acylation reactions. Finally, (S)‐ and (R)‐3‐(1‐hydroxyethyl)phenol (ee > 98%), key intermediates for the synthesis of important drugs, were prepared from the corresponding racemic diacetatethrough alkaline hydrolysis.
在本文中,我们描述了使用南极假丝酵母B(CAL-B)固定化脂肪酶作为生物催化剂轻松制备3-(1-羟乙基)苯酚的两种对映体的几种途径。我们已在温和的条件下在有机介质中使用Na 2 CO 3进行水解。以乙酸3-(1-乙酰氧基乙基)苯酯为底物,考察了反应参数的溶剂效应,脂肪酶的量和Na 2 CO 3的含量。在碱水解中,获得(R)-3-(1-羟乙基)苯酚,ee = 99%,而(S)-(-)-3-(1-乙酰氧基乙基)苯酚,ee最佳转化率(c = 50%)和高选择性(E> 200)时为98%。比较了另外两个脱酰反应:用MeOH和NEt 3的醇解。还检查了3-(1-羟乙基)苯酚与乙酸乙烯酯的酰化作用。碱性水解的结果最好,而在醇解和酰化反应中观察到良好的区域选择性和对映选择性。最后,由相应的外消旋二乙酸酯经碱水解制备(S)-和(R)-3-(1-羟乙基)苯酚(ee> 98%),这是合成重要药物的关键中间体。