Synthetic approaches toward the marine alkaloid prenostodione

An efficient synthesis of the core of prenostodione (3) is described herein featuring the base condensation of BOC-protected indole diesters 21 and 24 with p-methoxybenzaldehyde (22) and 4-[(t-butyldimethylsilyl)oxy]benzaldehyde (26). Attempts at selective saponification of the resultant diesters yielded isoprenostodione (3a) bearing the ester functionality at the C-3 position of the indole ring.