Preparative chiral separation and absolute configuration of the synthetic pterocarpanquinone LQB‐118

The racemic pterocarpanquinone LQB-118 is active, in mice and hamsters, against tegumentary and visceral leishmaniasis. This compound also presents antiinflammatory and antineoplastic activity in mice. The low level of toxicity observed in these studies makes LQB-118 a promising drug candidate. In order to conduct further biological testing to investigate enantioselectivity in the above-mentioned activities, a multimilligram amount of each enantiomer of LQB-118 was produced. Furthermore, vibrational circular dichroism (VCD) and Density Functional Theory (DFT) calculations were used to determine unambiguously their absolute configurations. The comparison of experimental and calculated VCD data led to the assignment of (−)-LQB-118 as 7aR,12aR and, consequently, (+)-LQB-118 as 7aS12aS.