60 rp 18 f254s

All reagents were purchased from Sigma Aldrich or Alfa Aesar and were used without further purification. The UV light source was provided by a Philips HB175 Facial Solarium (UVA, 365 nm, P = 4 × 15 W). Reverse phase column chromatography was carried out on Fluka Ltd silica gel 100 C18-reversed phase, under a positive pressure of compressed air. Analytical TLC analysis was performed using Merck 60 RP-18 F₂₅₄S aluminium-supported thin layer chromatography sheets and visualised using ninhydrin. ¹H and ¹³C NMR spectra were recorded on a Bruker Avance 400 (400 MHz, 100 MHz, respectively) or Bruker Avance III (500 MHz, 125 MHz, respectively). ¹H and ¹³C spectra were assigned using 2D NMR experiments including COSY, HSQC and HMBC. Melting points were performed on a Kofler Hotstage microscope and are uncorrected; the crystallisation solvent is shown in parentheses. IR spectra were recorded using a Bruker Tensor 27 spectrometer. Elemental analyses were submitted to the Elemental Analysis Service, London Metropolitan University. Optical rotations were recorded at 20 °C at the sodium D line (589 nm). ESG was prepared as previously reported.^{3 (link)} Selected examples of synthetic procedures are included below. Further details are available in the ESI.†

The BtD extract (5.5 g) was fractionated by successive open-column chromatography using silica gel as the stationary phase (60, F254, Merck KGaA, Darmstadt, Germany) and a gradient system n-hexane: ethyl acetate: methanol with ascending polarity. Fractions of 40 mL were collected and pooled into four subfractions (BtD1, BtD2, BtD3, and BtD4). BtD4 (116 mg) was acetylated and subfractioned into four subfractions (BtD4.1, BtD4.2, BtD4.3, and BtD4.4). Separation was monitored by TLC and HPLC. Aluminum plates coated with silica gel 60 F254 (normal phase, Merck) and silica gel 60 RP-18 F254S (reverse phase, Merck) were used. The plates were analyzed with an ultraviolet light lamp (UVGL-58, 254–365 nm UV) and specific developers. HPLC was performed with equipment consisting of a separation module chromatographic system (Waters 2695) and photodiode array detector (Waters 2996), as well as a 250 × 4 mm Licrosphere^® 100 RP-18 Column (5 μm particle size). The mobile phase consisted of gradient water: acetonitrile. Samples were analyzed at 400 μg/mL, with a flow of 0.9 mL/min and a sample injection of 10 μL. The detection of compounds was carried out between 195–600 nm [12 (link)].