Model 240 c

All chemicals, reagents, and solvents were bought from Sigma company and were used without further purification. The ¹H NMR spectra were recorded on a Bruker Unity 300 or 400 MHz spectrometer. The ¹³C NMR spectra were also recorded at 75 or 100 MHz. The chemical shifts are given in ppm and were referenced with the residual solvent resonances relative to tetramethylsilane (TMS). The mass spectra were obtained on a Finnigan MAT 312 mass spectrometer, connected to a PDO 11/34 (DEC) computer system by electron impact. The elemental analyses were determined using a Perkin Elmer Model 240-C instrument (PerkinElmer, Hopkinton, MA, USA). The melting points were measured on a SMP1 Stuart apparatus and are uncorrected. Flash chromatography was conducted using MERCK silica gel (mesh size 230–400 ASTM). Thin-layer chromatography (TLC) was performed on Macherey-Nagel poly gram Sil G/UV254 silica gel plates, with visualization under UV (254 nm).

Melting points are uncorrected. All ¹H NMR and ¹³C NMR spectra were recorded on spectrometer Varian Mercury Plus operating at 399.93 MHz and 100.57 MHz, respectively. Chemical shifts are given in ppm (δ) and coupling constants in Hertz; multiplicities are indicated by s (singlet), d (doublet), t (triplet), ddt (doublet doublet triplet), m (multiplet) or series of m (series of multiplet). CDCl₃, acetone-d6, were used as solvents as indicated below. Shifts are given in ppm relative to the remaining protons of the deuterated solvents used as internal standard (¹H, ¹³C). Elemental analyses were performed using an elemental analyser Perkin-Elmer model 240 C. Ethanol (EtOH) grade 96% was used, dry acetone was freshly distilled from CaCl₂ under N₂. All reagents were of commercial quality and used as purchased from various producers (Sigma-Aldrich, Merck). Magnolol 1 and honokiol 2 were purchased from Chemos GmbH, Germany. Flash chromatography was carried out with silica gel 60 (230–400 mesh, Kiesgel, EM Reagents) eluting with appropriate solution in the stated v:v proportions. Analytical thin-layer chromatography (TLC) was performed with 0.25 mm thick silica gel plates (Polygram^® Sil G/UV₂₅₄, Macherey-Nagel). The purity of all new compounds was judged to be >98% by ¹H-NMR spectral determination. Solvents were used without additional purification or drying, unless otherwise noted.