Asymmetric Synthesis and CD Investigation of the 1,4-Benzodioxane Lignans Eusiderins A, B, C, G, L, and M

The enantioselective synthesis of (-)-eusiderins A (1), B (2), G (25), L (23), M (5) and (+)-eusiderin C (20) and a range of analogues was undertaken using an efficient, divergent synthesis all from a single chiral aldehyde 15, which was derived from (S)-ethyl lactate 9. A comprehensive set of NMR data along with ECD spectra and optical rotation measurements of the synthesized natural products and analogues were then obtained. This data confirmed the absolute stereochemistry of eusiderins A (1) and C (20) and for the first time gives the ECD and optical rotation for eusiderins B (2), G (25), L (23), and M (5) and a range of other substituted 1,4-benzodioxanes. This data will now allow for the determination of absolute stereochemistry of other members in this class of compound.