Efficient access to both enantiomers of 3‐(1‐hydroxyethyl)phenol by regioselective and enantioselective CAL‐B–catalyzed hydrolysis of diacetate in organic media by sodium carbonate

Abstract

In the present paper, we describe several pathways employing immobilized lipase from Candida antarctica B (CAL‐B) as biocatalyst to prepare easily both enantiomers of 3‐(1‐hydroxyethyl)phenol. We have applied hydrolysis with Na2CO3 in organic media under mild conditions. The reaction parameters solvent effect, amount of lipase, and Na2CO3 were examined with 3‐(1‐acetoxyethyl)phenyl acetate as substrate. In alkaline hydrolysis, (R)‐3‐(1‐hydroxyethyl)phenol was obtained with ee = 99% and (S)‐(−)‐3‐(1‐acetoxyethyl)phenol with ee = 98% at optimal conversion (c = 50%) and high selectivity (E > 200). Two other deacylation reactions were compared: alcoholysis with MeOH and with NEt3. The acylation of 3‐(1‐hydroxyethyl)phenol 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 diacetate through alkaline hydrolysis.

Natrium Karbonat : Termodinamika dan Transport Ion

“…Proses produksi bahan alkali natrium karbonat sudah dilakukan dari zaman kuno sampai tahun 1800-an berupa pembakaran vegetasi darat dan air laut yang diikuti oleh proses kalsinasi pada panas (221;235) yang menyala (238;239) dan pencucian abu. Soda abu atau natrium karbonat yang diperoleh dengan cara ini merupakan bahan yang rendah; misalnya, Barilla Spanyol berisi 25 -30% natrium karbonat (33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46), Varec dari Normandia 3 -8%, dan rumput laut Skotlandia 10 -15%. Soda abu diperoleh dari tanaman (234;241) sangat mahal dengan menggunakan proses yang terlalu kuno untuk mendapatkan produk massal dan menghabiskan banyak vegetasi.…”

Practical access to (S)-heterocyclic aromatic acetates via CAL-B/Na2CO3-deacylation and Mitsunobu reaction protocol

“…In the present paper, we describe for the first time the kinetic resolution of few heterocyclic and heteroaromatic carbinols via enzymatic-alkaline hydrolysis, a simple and practical enzymatic hydrolysis method developed in our laboratory, with sodium carbonate in organic medium catalyzed by CAL-B lipase (Merabet-Khelassi et al 2012). This approach has been used effectively on many substrates such as arylalkylcarbinol acetates (Houiene et al 2013), N,O-protected amino alcohols (Alalla et al 2016), 2-aryl-1-cyclohexyl acetates (Belkacemi et al 2017) and 3-(1-hydroxyethyl)phenol (Braia et al 2018). This reaction has been integrated to the heterocyclic aromatic alcohols and incorporated to a deracemization process via stereoinversion (Bouzemi et al 2006;Houiene et al 2013) with the Mitsunobu esterification (Mitsunobu and Yamada 1967) to gave quantitatively access to the (S)-heterocyclic (aromatic) acetates.…”