P 1020 polarimeter

The reactions were performed using commercial reagents, and ACS grade solvents used for reactions were purified and dried in accordance with standard procedures. Column chromatography was performed on silica gel 60 (70–230 mesh), and reactions were monitored by TLC on Kieselgel 60 F254. The compounds were detected by examination under UV light and by charring with 5% sulfuric acid in methanol. Solvents were removed under reduced pressure at <40 °C. CH₂Cl₂ was distilled from CaH₂ directly prior to application. Pyridine was dried by refluxing with CaH₂ and then distilled and stored over molecular sieves (3 Å). Anhydrous DMF were used without further conditioning. Optical rotations were measured by using a Jasco P-1020 polarimeter. Unless noted otherwise, ¹H NMR spectra were recorded in CDCl₃ at 300 MHz (Bruker Advance) or at 500 MHz (Bruker ARX-500), ¹³C NMR spectra and two-dimensional experiments were recorded in CDCl₃ at 75 MHz (Bruker Advance) or at 125 MHz (Bruker ARX-500). The ¹H NMR chemical shifts are referenced to tetramethylsilane (TMS, δH = 0 ppm) or CDCl₃ (δH= 7.26 ppm) for ¹H NMR spectra for solutions in CDCl₃. The ¹³C NMR chemical shifts are referenced to the central signal of CDCl₃ (δC = 77.00 ppm) for solutions in CDCl₃. Accurate mass spectrometry determinations were performed using an Agilent 6230 ESI TOF LCMS mass spectrometer.