Fluka silica gel 60 plates

All solvents and reagents were purchased from Merck (Merck Bulgaria EAD, Darmstadt, Germany). Melting point was determined on a Boetius hot stage apparatus and was uncorrected. IR spectra were determined on a VERTEX 70 FT-IR spectrometer (Bruker Optics, Ettlingen, Germany). MP was characterized by ¹H NMR, ¹³CNMR, IR, and HRESIMS. The purity was determined by TLC using several solvent systems of different polarity. TLC was carried out on precoated 0.2 mm Fluka silica gel 60 plates (Merck Bulgaria EAD), using chloroform: diethyl ether: n-hexane = 6:3:1 as a chromatographic system. Neutral Al₂O₃ was used for column chromatographic separation. The product, after evaporation of the solvent, was purified by recrystallization from diethyl ether.

All reagents and chemicals were procured from commercial suppliers, namely Sigma-Aldrich S.A. and Riedel-de Haën, Sofia, Bulgaria, and used without further purification. NMR spectral data were acquired using a Bruker Avance Neo 400 spectrometer (BAS-IOCCP–Sofia, Bruker, Billerica, MA, USA). The ¹H-NMR and ¹³C-NMR spectra for all compounds were obtained in DMSO-d₆ at 400 MHz and 101 MHz, respectively. Chemical shifts are reported in relative ppm and were calibrated with respect to tetramethylsilane (TMS) at δ = 0.00 ppm, serving as the internal standard, with coupling constants denoted in Hz. NMR spectra were recorded at room temperature (approximately 295 K). For mass spectrometry (MS) analysis, a Q Exactive Plus high-resolution mass spectrometer (HRMS) with a heated electrospray ionization source (HESI-II) from Thermo Fisher Scientific, Inc., Bremen, Germany, was employed. The MS system was equipped with a Dionex Ultimate 3000RSLC ultrahigh-performance liquid chromatography (UHPLC) system from Thermo Fisher Scientific, Inc., Waltham, MA, USA. Thin-layer chromatography (TLC) was conducted using 0.2 mm Fluka silica gel 60 plates obtained from Merck KGaA, Darmstadt, Germany.