Salviamone, a norabietane diterpenoid from Salvia roborowskii Maxim and structural revisions of tanshinketolactone and prioketolactone

Abstract

One norabietane diterpenoid named salviamone (1) was isolated from the whole plants of Salvia roborowskii Maxim. Comparison of spectrometric data of 1 with the data of the previously reported tanshinketolactone and prioketolactone, strongly suggested that these metabolites were identical. Due to the existence of many quaternary carbons, we cannot fully determine the planar structure of these compounds through the 2D NMR spectrometric data. Thus, we suggested the structures of tanshinketolactone and prioketolactone were revised to salviamone by an analysis of statistical DP4+ analyses based on DFT-GIAO NMR calculations. Furthermore, the absolute configuration of 1 was determined for the first time by quantum chemistry ECD calculations.