Av 500 spectrometer

Unless otherwise noted, materials were obtained commercially and used without further purification. All the solvents were treated according to general methods. Flash column chromatography was performed over silica gel (300 to 400 mesh). See Supplementary Materials and Methods for experimental details.
¹H NMR spectra were recorded on a Bruker AV-400 spectrometer and a Bruker AV-500 spectrometer in chloroform-d₃. Chemical shifts are reported in parts per million (ppm) with the internal tetramethylsilane (TMS) signal at 0.0 ppm as a standard. The data are reported as follows: s = singlet, d = doublet, t = triplet, m = multiplet or unresolved, brs = broad singlet, coupling constant(s) in hertz, integration. ¹³C NMR spectra were recorded on a Bruker AV-400 spectrometer and a Bruker AV-500 spectrometer in chloroform-d₃. Chemical shifts are reported in ppm with the internal chloroform signal at 77.0 ppm as a standard. Mass spectra were recorded with a Micromass quadrupole/time-of-flight tandem mass spectrometer using electron spray ionization.

All commercial materials were used without further purification. Flash chromatography was carried out using Macherey-Nagel (Hoerdt, France) Kieselgel 60 M silica. Analytical thin layer chromatography was realized using aluminum-backed plates coated with Macherey-Nagel Kieselgel 60 XtraSIL G/UV254. Compounds were visualized under UV light (at 254 nm) or stained using KMnO₄. Nuclear magnetic resonance (NMR) spectra were recorded on a Bruker AVL300 or a Bruker AV400 or a Bruker AV500 spectrometer (Billerica, MA, USA), operating respectively at 300, 400, and 500 MHz for the proton (¹H) NMR. Carbon (¹³C) NMR spectra were recorded on a Bruker AVL300 or a Bruker AV400 spectrophotometer or a Bruker AV500 spectrometer, operating, respectively, at 75, 100, and 125 MHz. Chemical shifts were reported in parts per million (ppm) in the scale relative to residual solvent signals. Multiplicities are abbreviated as follows: s, singlet; d, doublet; t, triplet; dd, doublet of doublets; dt, doublet of triplts, m, multiplet; br, broad. Coupling constants were measured in Hertz (Hz). High-resolution mass spectra (HRMS) and low-resolution mass spectra were performed by the Centre Commun de Spectrométrie de Masse (CCSM), University of Lyon 1, Lyon, France. l- or d-homoserine lactone hydrobromide was synthesized as previously described [20 (link)].

One-dimensional (1D) NMR (500 MHz for ¹H NMR and 125 MHz for ¹³C NMR) and two-dimensional (2D) NMR (HSQC, HMBC, ¹H-¹HCOSY, ROSEY, or NOSEY) were measured on the Bruker AV-500 spectrometers (Bruker, Germany). The chemical shifts of ¹H and ¹³C NMR data were given in δ (ppm) and referenced to the solvent signal (CD₃OD, δ_H 3.31 and δ_C 49.00; DMSO-d₆, δ_H 2.50 and δ_C 39.52). High-resolution electrospray ionization mass spectroscopy (HRESIMS) data were acquired on an Agilent 6210 time-of-flight LC-MS instrument (Agilent Technologies Inc., Palo Alto, CA, USA). Optical rotation values were measured by JASCO P-1020 digital polarimeter (JASCO, Tokyo, Japan). IR spectrum data were recorded on Nicolet 380 Infrared Spectrometer (Thermo Fisher, Waltham, MA, USA). The electronic circular dichroism (ECD) data were determined using JASCO J-715 Spectropolarimeter (Jasco, Tokyo, Japan). The semipreparative high-performance liquid chromatography (HPLC) was equipped with an ODS column (250.0 mm×10.0 mm, 5 μm, Thermo Fisher Scientific, Waltham, MA, USA). Column chromatography (CC) was performed on silica gel (60–80 mesh or 200–300 mesh; Qingdao Marine Chemical Inc., Qingdao, China), Sephadex LH-20 (PharmaciaBiotec, Uppsala, Sweden), and ODS (40–70 µm, Nacalai Tesque, Kyoto, Japan).

Ultraviolet spectral were obtained on a Waters 2695 high performance liquid chromatography (HPLC) instrument with a photo diode array detector (Waters, Massachusetts, USA). Preparative HPLC was carried out on a Shimadzu LC-6AD instrument (Shimadzu, Kyoto, Japan) with a UV–Vis detector (SPD-20A), using a YMC-Pack-ODS-A column (250 × 20 mm, 5 μm) (YMC, Kyoto, Japan). The carbohydrates were measured by ion chromatography using an amperometric detector (Metrohm, Herisau, Switzerland) with a Hamilton RCX-30 column (250 × 4.6 mm, 7 μm) (Hamilton, Nevada, USA). Nuclear magnetic resonance (NMR) spectra were obtained using Bruker AV-500 spectrometers (500 MHz for ¹H NMR and 125 MHz for ¹³C NMR) (Bruker, Zurich, Switzerland). Chemical shifts (δ) are given in ppm, with TMS as an internal standard, and coupling constants (J) are in Hz. High-resolution electrospray ionisation-mass spectrometry (HRESIMS) spectra were obtained using an Agilent 6540 ultra-performance liquid chromatography (UPLC) with high-resolution quadrupole time-of-flight (Q-TOF) mass spectrometer (Agilent, California, USA), using an RRHD Eclipse Plus C₁₈ column (150 × 2.1 mm, 1.8 μm) (YMC, Kyoto, Japan)^{36 (link)}.

The optical rotations were measured with a Jasco P-1010 polarimeter. The UV spectra were recorded with a PerkinElmer UV–Vis spectrophotometer. Infrared (IR) spectra were recorded using a PerkinElmer Frontier Optica FT–IR spectrometer. The 1D and 2D NMR spectra recorded using a 500 MHz Bruker AV-500 spectrometer. Chemical shifts are reported in parts per million (δ) and coupling constants (J) are expressed in hertz. The HRESIMS were carried out on a QTOF 6540 UHD mass spectrometer (Agilent Technologies, Santa Clara, CA, USA). Chiral HPLC was performed on a CHIRALCEL OD-H column of 4.6ϕ—250 mm and attached to Agilent Technologies 1260 Infinity II. Silica gel G60 (60–200 µm, SiliCycle^® Inc., Québec, QC G1P 4S6, Canada) was used to perform column chromatography (CC). Precoated plates of silica gel (60F254, Merck, Kenilworth, NJ, USA) were used for analytical purposes.