Varian 400

PTHF₂₉₀₀ modification was performed in bulk via microwave-assisted transesterification (3 min at 550 W for 150 g polyol) [33 (link)] with two fold molar excess of methacrylic anhydride. Subsequent vacuum distillation separate α,ω-polytetrahydrofuran-dimethacrylate (PTHF₂₉₀₀-DM) from unreacted methacrylic anhydride and methacrylic acid formed during the reaction. A total of 500 ppm of BHT, was added to the mixture to prevent unwanted polymerization. Modification and purity were monitored by ¹H-NMR using a Varian 400 (Varian, Waldbronn, Germany) and ATR FT-IR (Vertex 70, Bruker, Ettlingen, Germany) spectroscopy. The developed procedure is completely solvent free and enables fast and easy recycling of excess methacrylic anhydride and methacrylic acid (Figure 3).

Optical rotation was measured with a Jasco P2000 polarimeter (Jasco Corporation, Tokyo, Japan), and FT-IR spectra using a Jasco FT/IR-4200 (Jasco corporation, Japan). ECD and UV spectra were recorded with an Applied Photophysics Chirascan-plus CD spectrometer. ¹H, ¹³C and 2D NMR spectra were obtained on a Varian 400 (Varian, Palo Alto, CA, USA)-400MHz. Waters Xevo G2 Q-TOF, (Waters, Milford, MA, USA) spectra were measured on a Q-TOF mass spectrometer. Semi-preparative high-performance liquid chromatography (HPLC) was performed on a Gilson 321 pump, Gilson 172 Diode Array Detector (Gilson, Middleton, WI, USA). YMC-pack Ph, 250 × 20 mm (YMC, Tokyo, Japan) and Luna 5u C18 column 250 × 10 nm (Phenomenex) as HPLC columns were used. MPLC was run on Isolera One (Biotage, Cardiff, UK). Solvents for HPLC were acetonitrile (MeCN) (HPLC grade) and methanol (HPLC grade), purchased from SK Chemical (Seoul, Korea). Water was purified using a MIlli-Q system (Millipore, Bedford, MA, USA). Column chromatography was performed on C-18 RP silica gel (Cosmosil, Kyoto, Japan) and Sephadex LH-20 (GE Healthcare, Stockholm, Sweden). TLC analysis was run on silica gel 60 F₂₅₄ plates (Marck, Darmstadt, Germany). The spots were visualized by spraying with 10% aqueous H₂SO₄.