Spectroscopic Analysis of Chemical Compounds

Melting points were determined with a Mel-Temp apparatus using capillary tubes and are uncorrected. Proton nuclear magnetic resonance spectra (¹H NMR) were recorded using an ARX300 300 MHz Bruker NMR spectrometer. IR spectra were obtained with a PerkinElmer 1600 series FTIR spectrometer. The purities of all of the biologically tested compounds were estimated by HPLC, and in each case, the major peak accounted for ≥95% of the combined total peak area when monitored by a UV detector at 254 nm. HPLC analyses were performed on a Waters 1525 binary HPLC pump/Waters 2487 dual λ absorbance detector system. HPLC analyses were performed on a Sunrise C-18 column with dimensions of 16 × 4.6 cm and 5 μm particle size. Analytical thin-layer chromatography was conducted on Baker-flex silica gel IB2-F plates, and compounds were visualized with UV light at 254 nm. Silica gel flash chromatography was performed using 230–400 mesh silica gel. The anhydrides 11a and 11b and compound 12 were prepared according to the literature and showed similar spectroscopic data.^{38 (link),45}