Various Polar Tripeptides as Asymmetric Organocatalyst in Direct Aldol Reactions in Aqueous Media

Abstract

A series of tripeptide organocatalysts containing a secondary amine group and two amino acids with polar side chain units were developed and evaluated in the direct asymmetric intermolecular aldol reaction of 4-nitrobenzaldehyde and cyclohexanone. The effectiveness of short polar peptides as asymmetric catalysts in aldol reactions to attain high yields of enantio- and diastereoselective isomers were investigated. In a comparison, glutamic acid and histidine produced higher % ee and yields when they were applied as the second amino acid in short trimeric peptides. These short polar peptides were found to be efficient organocatalysts for the asymmetric aldol addition reaction in aqueous media.

Highly enantioselective asymmetric direct aldol reaction promoted by aziridine amides constructed on chiral terpene scaffold

“…1 H and 13 C NMR spectra were in agreement with the literature . The ee was determined by chiral HPLC (Chiral AD‐H, i PrOH/ n ‐hexane 10/90, flow: 1 ml/min., λ = 254 nm): t R = 7.70 min.…”

“…Taken from the literature (on the basis of optical rotation signs and retention times in HPLC chromatograms).…”

“…2.3.5 | (4S)-Hydroxy-4-(4′trifluoromethylphenyl)-butan-2-one 1 H and 13 C NMR spectra were in agreement with the literature. 41 The ee was determined by chiral HPLC (Chiral AD-H, i PrOH/n-hexane 10/90, flow: 1 ml/min., λ = 254 nm): t R = 7.70 min. (major), t R = 8.92 min.…”

“…Such conformation forces a specified position of the aziridine ring. Because of the steric hindrance, only the orientation of the aziridine Taken from the literature [38][39][40][41] (on the basis of optical rotation signs and retention times in HPLC chromatograms).…”

A Pseudopeptide Polymer Micelle Used for Asymmetric Catalysis of the Aldol Reaction in Water

“…3 Diastereomeric ratio, determined by 1 H NMR (CDCl 3 ). 4 Determined by HPLC with chiral column (Figure S8); the absolute configuration of the products was deduced by comparing the retention time with reported values [43,44,45]. 5 M n ≈ 5800, M w / M n = 1.28 [24].…”