Inova instrument

The UV spectrum (200–500 nm) was measured using a PerkinElmer Lambda-25 UV spectrophotometer. IR spectra (200–4,000 cm^-1) were recorded on an FT–IR PerkinElmer RX-1 spectrometer. The mass spectrum was recorded using a micromass Quattro II triple quadrupole mass spectrometer. 1H and 13C nuclear magnetic resonance (NMR) spectra were obtained using a 300 MHz Varian Inova instrument in deuterated water (D2O). Elemental analysis was performed using a Carlo Erba 1106 CHNO/S elemental analyzer. The melting point was determined using a WRS-1B digital melting-point apparatus (Singh et al., 2013 (link)).

NMR spectra were recorded on a Varian Inova instrument (500 MHz) at 25 °C in CDCl₃, and CD₃OD using tetramethyl silane (TMS) as an internal standard. The NMR solvents CDCl₃ and CD₃OD were purchased from Cambridge Isotope Laboratories (Tewksbury, MA, USA). Chemical shifts (δ) were reported in parts per million (ppm) and coupling constant values (J) in Hertz (Hz) relative to CDCl₃ (1H, δ 7.26; 13C, δ 77.00) or CD₃OD (1H, δ 3.4, 4.8; 13C, δ 49.3) and tetramethyl silane. The following abbreviations were used for signal multiplicities: s = singlet; d = doublet; t = triplet; q = quartet, and m = multiplet. All other solvents were of reagent grade and were purchased from Kanto Chemical (Tokyo, Japan). ESI-MS spectra were recorded on a JEOL JMS-T100LP spectrometer (JEOL, Akishima, Japan). Melting points were measured on a Micro Melting Point Apparatus (Yanaco Co., Ltd., Kumiyama, Japan). Analytical thin-layer chromatography (TLC) was performed on 0.2 mm silica gel plates (Merck 60 F-254), (Darmstadt, Germany), developed with CHCl₃:MeOH:H₂O (65:35:10, lower phase) and sprayed with a mixture of 5% ammonium molybdate and 1% cerium (IV) sulphate in 3.6 N H₂SO₄ (Hanessian stain solution), or viewed with a handheld UV lamp (UVGL-58) at 254 nm.

All chemicals were purchased from Sigma-Aldrich Chemical Co. The solvent was removed at aspirator pressure using a rotary evaporator. TLC was performed with Merck precoated TLC plates, and the compounds were made visible using a fluorescent inspection lamp and iodine vapor. Gravity chromatography was done with Merck silica gel 60 (mesh size 63–200 μm). Nuclear magnetic resonance spectra were recorded on a Varian Inova instrument, operating at 500 MHz for ¹H NMR and 75 MHz for ¹³C NMR. Chemical shifts (δ) for ¹H NMR spectra are reported in ppm downfield relative to the center line of CDCl₃ triplet at 7.26 ppm. Chemical shifts for ¹³C NMR spectra are reported in ppm downfield relative to the center line of CDCl₃ triplet at 77.23 ppm. The abbreviations s, d, t, and m stand for the resonance multiplicities singlet, doublet, triplet, and multiplet, respectively. ¹³C spectra, are ¹H decoupled, and multiciplities were determined by APT pulse sequence. The melting points were recorded on a Boëtius hot plate microscope. FT-IR spectra were recorded on FT-IR Shimadzu spectrometer (4000–400 cm⁻¹. EI-MS and HRMS were performed with Finnigan MAT 95, EI: 70 eV, R:10000.