Maxis impact spectrometer

NMR spectra were acquired on a
Bruker Ultra Shield 700 instrument, running at 700 MHz for ¹H and 176 MHz for ¹³C. Chemical shifts (δ) are reported
in ppm relative to residual solvent signals (CDCl₃: 7.26
ppm for ¹H NMR, 77.16 ppm for ¹³C NMR). Mass
spectra were recorded on a Bruker Maxis Impact spectrometer using
electrospray (ES+) ionization (referenced to the mass of the charged
species). Analytical thin layer chromatography (TLC) was performed
using pre-coated aluminum-backed plates (Merck Kieselgel 60 F254)
and visualized by ultraviolet irradiation. Unless otherwise noted,
analytical-grade solvents and commercially available reagents were
used without further purification. For flash chromatography (FC),
silica gel (w/ Ca, ∼0.1%, 230–400 mesh), green LED (50
W, λ = 525 nm), and blue LED (50 W, λ = 456 nm) were purchased
from commercial supplier Kessil LED Photoreactor Lightning. Fluorescence
measurements were performed using a Varian Cary Eclipse spectrofluorometer
equipped with a thermostatted cell holder. Coumarine-3-carboxylic
acids 1b–k were synthesized according
to the literature procedure.^{13 (link)} Catalyst 4c was synthesized according to the literature procedure.^{14 (link)}

NMR spectra were acquired on a Bruker Ultra Shield 700 instrument (Bruker Corporation, Billerica, MA, USA), running at 700 MHz for ¹H and 176 MHz for ¹³C, respectively. Chemical shifts (δ) were reported in ppm relative to residual solvent signals (CDCl₃: 7.26 ppm for ¹H NMR, 77.16 ppm for ¹³C NMR). Mass spectra were recorded on a Bruker Maxis Impact spectrometer using electrospray (ES+) ionization (referenced to the mass of the charged species). Analytical thin layer chromatography (TLC) was performed using pre-coated aluminum-backed plates (Merck Kieselgel 60 F254) and visualized by the ultraviolet irradiation or I₂ stain. Unless otherwise noted, analytical grade solvents and commercially available reagents were used without further purification. For flash chromatography (FC), silica gel (Silica gel 60, 230–400 mesh, Merck, Darmstadt, Germany) was used. The enantiomeric ratio (er) of the products were determined either by ultra performance convergence chromatography (UPC2) using Daicel Chiralpak IA and IG columns as chiral stationary phases or by chiral stationary phase HPLC (Daicel Chiralpak IF column). Azlactones 1 were synthetized according to the literature procedure [80 (link)]. Chromone-3-carboxylic acids 2 were prepared from the corresponding 2-hydroxyacetophenones following the literature procedure [81 (link)].

NMR spectra were acquired on a Bruker Ultra Shield 700 instrument (Bruker Corporation, Billerica, MA, USA), running at 700 MHz for ¹H and 176 MHz for ¹³C, respectively. Chemical shifts (δ) were reported in ppm relative to residual solvent signals (CDCl₃: 7.26 ppm for ¹H NMR and 77.16 ppm for ¹³C NMR). Mass spectra were recorded on a Bruker Maxis Impact spectrometer using electrospray (ES+) ionization (referenced to the mass of the charged species). Analytical thin layer chromatography (TLC) was performed using pre-coated aluminium-backed plates (Merck Kieselgel 60 F254) and visualized by ultraviolet irradiation. Unless otherwise noted, analytical-grade solvents and commercially available reagents were used without further purification. For flash chromatography (FC), silica gel (Silica gel 60, 230–400 mesh, Merck, Darmstadt, Germany) was used. The enantiomeric ratio (er) of the products were determined by chiral stationary phase HPLC by Ultra Performance Convergence Chromatography (UPCC), using Daicel Chiralpak IA, IB, IC, and IG columns as chiral stationary phases. Diethyl iminomalonates 3 and iminodihydrofuran-2-one 4 were prepared from the corresponding 2-hydroxyaldehyde following the literature procedure [46 (link)]. Chromone-3-carboxylic acids 2 were prepared from the corresponding 2-hydroxyacetophenones following the literature procedure [47 (link)].

For the identification of the various compounds present in the extract, the high-resolution mass spectrum was measured on a Maxis Impact spectrometer (Bruker Daltonik GmbH, Bremen, Germany) using direct infusion ESI Q-TOF MS. The spectrometer was operated in linear positive mode in the m/z range of 50–600 Da, under the following conditions: 3.5 kV potential between spray needle and orifice, 0.4 bar nebulizer pressure, 3.0 L·min⁻¹ drying gas flow rate at 200 °C, and 3.0 µL·min⁻¹ sample flow rate [38 (link)]. The analysis was outsourced at the Laboratorio de Técnicas Instrumentales facilities of Universidad de Valladolid.

All reagents were purchased from either Sigma‐Aldrich, Acros Organics or Fluorochem and were used without further purification. Solvents used for reactions and workups were purchased from Fisher Chemical (HPLC grade). Deionized and milliQ water were obtained from an Elga Water Purification system. All amino acids were N‐Fmoc protected and side chains were protected with; Trt (Cys, hCys); Mtt (Lys) and OPip (Asp). The evaporation of solvents was achieved using a Büchi R3 with a Vacubrand CVC3000 vacuum pump and condenser connected to a recirculating cooler system Julabo F1000. LC‐MS analyses were conducted on a ThermoScientific Dionex UltiMate 3000 and high‐resolution mass spectrometry (HR‐MS) data were recorded using electrospray ionization in positive mode (ESI+) with a Bruker MaXis Impact spectrometer. Preparative HPLC experiments were performed using an Agilent 1260 Infinity instrument with a Jupiter Proteo 90 Å 250 × 21.2 mm, 10 μm preparative column. Analytical HPLC experiments were performed using an Agilent 1290 Infinity LC series system equipped with an Ascentis Express Peptide ES‐C18 100 × 2.1 mm column, 2.7 μm particle size on a 5%‐50% gradient of acetonitrile in water (with 0.1% formic acid) over 10 min.

Some of these reactions were carried out in screw-capped tubes and other reactions under nitrogen or argon and ethylene atmosphere in oven-dried glassware. Air- and moisture-sensitive reactions were performed in degassed solvents. Transfer of moisture-sensitive materials were carried out using standard syringe−septum techniques. All the commercial grade reagents were used without any purification until otherwise specified. Melting points were recorded on a Veego or Büchi melting point apparatus and are uncorrected. NMR Spectra were generally recorded on Bruker (Avance 400 or Avance III 500) spectrometers operated at 400 or 500 MHz for ¹H and 100 or 125.7 MHz for ¹³C nuclei. NMR Samples were generally made in chloroform-d solvent, and chemical shifts (δ values) are reported in parts per million (ppm). Coupling constants (J values) were reported in hertz (Hz). HRMS measurements were carried out using a Bruker (Maxis Impact) spectrometer. IR spectra were recorded on a Nicolet Impact-400 or Cary 630 FTIR spectrometer.