Discussion of absolute configuration for bioactive Griseusins by comparing computed optical rotations and electronic circular dichroism with the experimental results

Absolute configurations of seven bioactive natural Griseusins were investigated. Optical rotation and electronic circular dichroism were calculated at the B3LYP/6-311++G(2d,p)//PCM/B3LYP/6-311++G(2d,p) or other levels in the gas phase and/or in solution. Computational results exhibited that the early reported absolute configuration of four among the seven may not be the best structures after comparing the computed optical rotations, electron circular dichroisms to the experimental data. Then four favorable structures are suggested based on the comparison of predicted optical rotations and electronic circular dichroisms to the experimental results. It is the first time to find that the different position of carbonyl group on aromatic ring (planar structure changes) in Griseusins can lead to the ECD curve reversed instead of the stereogenic center changes. In traditional opinion, ECD curve reversal happens only when stereogenic center configuration reverses, such as from AC of (R) to (S).