Aromatic diglycosides from and a multi-step conformer filtering procedure for TDDFT calculation of flexible glycoside.

Three previously undescribed aromatic diglycosides (, , and ) and six known analogs (, , , and ) were isolated from the roots and rhizomes of Gagnep. Their structures were elucidated by detailed spectroscopic analysis. The absolute configuration of compound was determined by comparing the experimental and TDDFT calculated ECD spectra of and aglycone . Furthermore, a multistep conformer filtering procedure for TDDFT calculation of flexible glycoside was proposed, which afforded high accuracy with acceptable computing cost in determining the absolute configuration of glycosides using quantum calculated ECD.