Enantiomeric pairs of meroterpenoids from Rhododendron fastigiatum

Five pairs of optically pure meroterpenoid enantiomers ( 1a/1b-5a/5b ) and two known compounds ( 6 and 7 ) were isolated from Rhododendron fastigiatum. Compounds 1a/1b-5a/5b were resolved from naturally scalemic mixtures by chiral HPLC. Their structures were elucidated by spectroscopic methods, X-ray crystallographic experiments, and ECD analyses. Compounds 1a/1b , 2a/2b , 3b , 4a/4b , and 5a/5b were new meroterpenoids with different polycyclic systems. Two enantiomeric pairs ( 2a/2b and 3a/3b ), 6 , and 7 exhibited inhibitory effects on protein tyrosine phosphatase 1B (PTP1B) in vitro.