6540 series q tof

HPLC purifications were carried out on an Agilent 1200 Series analytical HPLC system equipped with a photo diode array detector and an automated fraction collector, or on an Agilent 1200 Series preparative HPLC system also equipped with the same modules. Low resolution HPLC-ESI-MS analysis was performed on an Agilent 1200 Series HPLC system equipped with a diode array detector and a 6130 Series ESI mass spectrometer using an analytical Phenomenex Luna C18 column (5 μm, 4.6 × 100 mm) operating at 0.5 mL/min with a gradient of 25% MeCN in H₂O (+0.1% formic acid, FA) to 100% MeCN (+0.1% FA) over 20 min. High resolution (HR) ESI-MS and HR-tandem MS (HR-MS/MS) were carried out on a 6540 UHD Accurate Mass Q-tof HPLC-MS system (Agilent), equipped with a 1260 Infinity Series HPLC, an automated liquid sampler, a diode array detector, a JetStream ESI source, and the 6540 Series Q-tof. The ESI-MS was calibrated to within 1 ppm prior to analysis, and samples were resolved on an Agilent C18 Eclipse column (2.7 μm, 3 × 50 mm) at a flow rate of 0.4 mL/min using water and MeCN as mobile phases (plus 0.1% FA). ¹H and 2D NMR spectra were recorded at the Princeton Chemistry NMR Core Facility on a Bruker Avance III 500 MHz spectrometer equipped with a ¹H-optimized cryoprobe. Roseobactin NMR spectra were obtained in D₂O and 9:1 H₂O/D₂O; chemical shifts were referenced to the residual solvent peak.