文摘
Good agreement between theoretical and experimental vibrational circular dichroism curves of (1S,11S,12S)-(+)-verticilla-3E,7E-dien-12-ol (1) established the absolute configuration of this natural diterpene isolated from Bursera suntui.Molecular modeling of 1 was carried out using the Monte Carlo protocol followed by geometry optimization at theB3LYP 6-31G(d,p) level of theory. The 12-membered ring of 1 was found in a single preferred chair-chair-chair-chair conformation. In the six-membered ring a chair prevails over a distorted boat, and the C-OH bond rotationgenerates three predominant rotamers. Validation of the minimum energy conformation for 1 was achieved by comparisonof theoretical and experimental infrared frequencies, vicinal 1H NMR coupling constants, and X-ray diffraction data.This study confirms that (+)-verticillol 1 isolated from Bursera species has the 1S,11S,12S absolute configuration thatcorresponds to the same enantiomeric series as verticillanes from Sciadopitys and Taxus, while verticillanes from Jackiellaand Jungermannia have antipodal structures.