A novel tetrahydroquinoline acid and a new racemic benzofuranone from Capparis spinosa L., a case study of absolute configuration determination using quantum methods

A novel tetrahydroquinoline acid (1) and a new racemic benzofuranone (2), were isolated from the stems and fruits of Capparis spinosa L., using different column chromatography. The new benzofuranone was further separated by HPLC via chiral column to yield enantiomers (−)-2a and (+)-2b. The structures are so simple that some characteristics exhibited very close. This caused the difficulty in stereochemistry study. To overcome the difficulties, a comprehensive method is used for their stereochemistry study, such as computations of 13C NMR, optical rotation and electronic circular dichroism.