Asymmetric cross-aldol reaction of isatin and ketones catalyzed by crude earthworm extract as efficient biocatalyst

Abstract

The asymmetric cross-aldol reaction of simple ketones (acetone, cyclohexanone) with isatin derivatives in the presence of crude extract from earthworms as green and effective biocatalyst proceeds easily in MeCN/H 2 O (1:1) as solvent to afford 3-hydroxy-2-oxindoles derivatives. Ten compounds were synthesized in high yields (62-88%) and moderate ee (29-42%). Structure of the synthesized compounds has been characterized on the basis of NMR spectra and CHN analysis. The ee of the obtained compounds was determined by chiral phase HPLC analysis.

Aldol Insights: The Route to Chiral Synthesis of 3‐Substituted 3‐Hydroxy‐2‐Oxindoles

“…Among these approaches, Rouhani and colleagues presented a distinctive environmentally friendly strategy for the asymmetric cross-aldol reaction of isatin with common ketones such as acetone and cyclohexanone. [50] In this innovative process, a crude extract from earthworms served as a green and efficient biocatalyst. The reactions were conducted in a solvent mixture of MeCN/ H 2 O (1 : 1), resulting in the synthesis of 3-hydroxy-2-oxindole derivatives 3.…”

“…Unlike traditional approaches, these catalytic systems bring forth unique attributes that influence the stereochemical outcomes of the aldol reaction, offering new avenues for the construction of chiral and complex molecules. Among these approaches, Rouhani and colleagues presented a distinctive environmentally friendly strategy for the asymmetric cross‐aldol reaction of isatin with common ketones such as acetone and cyclohexanone [50] . In this innovative process, a crude extract from earthworms served as a green and efficient biocatalyst.…”

Chiral Ionic Liquids Based on l-Cysteine Derivatives for Asymmetric Aldol Reaction

“…Proline is an abundant, non-toxic, inexpensive, and easily available, in both enantiomeric forms, amino acid. L-proline, "the simplest enzyme" [10,11], has been proven to promote many reactions and deliver products with high stereoselectivity [12][13][14][15][16][17][18][19]. Along the years, L-proline has been found to enantioselectively catalyse reduction, oxidation, electrophilic α-fluorination or amination, as well as carbon-carbon bond-forming reactions, i.e., the aldol reaction.…”