Structural Elucidation by NMR Analysis Assisted by DFT Calculations of a Novel Natural Product from Conchocarpus Mastigophorus (Rutaceae)

The stem of Conchocarpus mastigophorus was solvent‐extracted and purified by silica‐gel column chromatography to afford eleven natural products, including one new compound. The structures of all compounds were fully elucidated by spectrometric methods. NMR analyses assisted by theoretical calculations were used to determine the structure of a novel natural product. The structure of the novel compound 2 (acridone alkaloid) was established as 1,3,6‐trihydroxy‐2,4,5‐trimethoxy‐10‐methylacridin‐9(10H)‐one. The absolute configuration of compound 1 was assigned by means of vibrational circular dichroism (VCD) spectroscopy. The structure of compound 1 was defined as (3S)‐(−)‐3‐hydroxy‐1‐methylpiperidin‐2‐one. Theoretical calculations were performed at the B3LYP/6‐311+G(2d,p)//M06‐2X/6‐31+G(d,p) level of theory and DP4 statistical tool was employed to compare the calculated and experimental NMR chemical shifts.