Three unprecedented oligomeric phenylpropanoids with new carbon skeletons [(+)/(–)-maglignan A ((+)/(–)-1) and maglignan B (2)] and an undescribed meroterpenoid [maglignan C (3)] possessing an oxabicyclo [3.3.1] skeleton were obtained from the bark of Magnolia officinalis var. biloba. Compounds (+)-1 and (–)-1, a pair of enantiomeric trimers with novel oligomerization mode, which could be biosynthesized through oxidation, substitution, and hetero-Diels–Alder (HDA) reactions between C6–C3 units, exhibited significant inhibition of PTP1B and α-glucosidase with IC50 values from 0.448 to 2.16 μM. Molecular docking simulation was conducted to demonstrate the obtained results.
