Total Synthesis and Absolute Configuration Determination of the α-Glycosidase Inhibitor (3 S ,4 R )-6-Acetyl-3-hydroxy-2,2-dimethylchroman-4-yl ( Z )-2-Methylbut-2-enoate from Ageratina grandifolia .

Herein, we report the first total synthesis of α-glycosidase inhibitor (3 R , 4 S )-6-acetyl-3-hydroxy-2,2-dimethylchroman-4-yl ( Z )-2-methylbut-2-enoate as well as its enantiomer. Our synthesis confirms the chromane structure separately proposed by Navarro-Vazquez and Mata, on the basis of DFT computations. Furthermore, our synthesis allowed us to determine the absolute configuration of the natural compound as (3 S , 4 R ) and not (3 R , 4 S ).