Hybrid Catalysis of 8-Quinolinecarboxaldehyde and Brønsted Acid for Efficient Racemization of α-Amino Amides and Its Application in Chemoenzymatic Dynamic Kinetic Resolution

Information1 H NMR spectra were recorded on a JEOL JNM-ECS400 (400 MHz) and JEOL JNM-ECA600II (600 MHz) spectrometer.Chemical shifts are reported in ppm from the tetramethylsilane (0.0 ppm) resonance as the internal standard.Data are reported as follows: chemical shift, integration, multiplicity (s = singlet, d = doublet, t = triplet, and br = broad) and coupling constants (Hz). 13C NMR spectra were recorded on a JEOL JNM-ECA600II (151 MHz) spectrometer with complete proton decoupling.Chemical shifts are reported in ppm from the solvent resonance as the internal standard (CDCl3; 77.23 ppm or CD3OD; 49.15 ppm).Optical rotations were measured on a HORIBA SEPA-500 polarimeter.The high-resolution mass spectra were measured on Thermo Fisher Scientific Exactive Plus (ESI).Analytical thin layer chromatography (TLC) was performed on Merck precoated TLC plates (silica gel 60 GF254, 0.25 mm).Flash column chromatography was performed on Silica gel 60 N (spherical, neutral, 40~50μm; Kanto Chemical Co., Inc.).Enantiomeric excesses were determined by HPLC analysis using chiral columns (φ 4.6 mm x 250 mm, DAICEL CHIRALPAK AZ-3 (AZ3) and CHIRALPAK IB N-3 (IBN3)) with hexane (H), isopropyl alcohol (IPA), and ethanol (EtOH) as eluent.Toluene was supplied from Kanto Chemical Co., Inc. as "Dehydrated" and further purified by both A2 alumina and Q5 reactant using a GlassContour solvent dispensing system.Water was deionized with a Millipore system as a Milli-Q grade.Immobilized CALB was purchased from Sigma-Aldrich (Lipase acrylic resin, >=5,000 U/g, recombinant, expressed in Aspergillus niger) and used as such.Phenylglycine derivatives were synthesized by following the literature methods. 1