(+)/(−)-Alexanoid A, a pair of enantiomeric sesquiterpenoid with a novel 5/6/6 tricyclic backbone from the stem of Syringa pinnatifolia

Abstract

A pair of enantiomeric sesquiterpenoid, namely (+)/(−)-alexanoid A (1a and 1b), with an unprecedented 4,11,11-trimethyltricyclo[6.3.1.01,5] dodecane skeleton (proposed alexane), was discovered from the peeled stems of Syringa pinnatifolia Hemsl. The structures were elucidated by the spectroscopic data analysis including NMR, UV, IR, optical rotation (OR), and electronic circular dichroism (ECD) calculation, and the protective activity on H9c2 cardiomyocytes and anti-inflammatory activity against NO production in lipopolysaccharide (LPS)-induced RAW264.7 cells were evaluated.