Silica gel g precoated plates

The IR spectra (KBr pellets) were run on a 380 FT-IR instrument from Nicolet (Thermo, Pittsburgh, PA, USA). The HRMS were recorded with an API QSTAR Pulsar mass spectrometer (Bruker, Bremen, Germany). The UV spectra were obtained from a DU-800 spectrometer (Beckman, Brea, CA, USA). Optical rotations were measured on an Autopol III polarimeter (Rudolph, Hackettstown, NJ, USA). CD spectra were recorded with a J-815 spectrometer (JASCO, Tokyo, Japan). The NMR spectra were recorded on an AV-500 spectrometer (500 MHz for ¹H-NMR and 125 MHz for ¹³C-NMR; Bruker), using the solvent residue signal as the internal standard. Column chromatography was performed with ODS gel (20–45 mm, Fuji Silysia Chemical Co. Ltd., Durham, NC, USA), Sephadex LH-20 (Merck, Darmstadt, Germany) and silica gel (60–80, 200–300 mesh, Qingdao Haiyang Chemical Co. Ltd., Qingdao, China). TLC was carried out on silica gel G precoated plates (Qingdao Haiyang Chemical Co. Ltd.), and spots were detected by spraying with 5% H₂SO₄ in EtOH followed by heating.

¹D-and ²D-NMR experiments were recorded on Bruker AVANCE IIITM 600 MHz or Bruker AVIII 500 MHz spectrometers (Bruker, Bremen, Germany). Chemical shifts were referenced to the solvent residual peaks. The HRESIMS were acquired using an API Qstar Pulsar mass spectrometer (Bruker, Bremen, Germany). Optical rotations were recorded on an MCP 5100 polorimeter (Anton Paar, Graz, Austria). IR spectra were measured on a Nicolet 380 FT-IR spectrometer (Thermo, Pittsburgh, PA, America). HPLC analysis was performed on Agilent Technologies 1260 Infinity II (Agilent, Palo Alto, CA, USA) with a reversed-phased column (YMC-packed C18, 5 μm, 250 mm × 10 mm) using a Dionex P680 pump and detected with a Dionex UVD 170 U detector (λ = 254 nm). Silica gel (60–80, 200–300 mesh, Qingdao Marine Chemical Co. Ltd., Qingdao, China), ODS gel (20–45 μm, Fujian Silysia Chemical Co. Ltd., Fuzhou, China) and Sephadex LH-20 (40–70 μm, Merck, Darmstadt, Germany) were used for column chromatography. TLC was carried out on Silica gel G precoated plates (Qingdao Haiyang Chemical Co. Ltd., Qingdao, China), and the peaks on TLC were detected by a UV lamp at 254 nm and then sprayed with 5% H₂SO₄ in EtOH. The methanol used for HPLC analysis was of chromatographic grade (Concord Technology Co. Ltd., Tianjin, China). Tacrine hydrochloride hydrate (99%) and paclitaxel (99%) were purchased from Sigma Chemical.