Starting from unsymmetrically O-protected methyl 4-bromo-3,5-dihydroxybenzoate, a
facile synthesis of the methyl ether of bioactive natural product NG-121 was accomplished
in very good overall yield. The key steps were: Stille coupling reaction of the farnesyl
unit with the electron-rich phenolic segment; hydroxy-directed selective epoxidation
of the farnesyl chain along with concomitant phenol-driven intramolecular regio- and
diastereoselective ring closure to the corresponding hydroxybenzopyran; and regioselective
formylation followed by in situ reductive lactonization.
Key words
4-bromo-3,5-dihydroxybenzoate - Stille coupling - intramolecular cyclization - formylation
- lactonization - NG-121 methyl ether
