Soft-enolization Baker-Venkataraman Rearrangement Enabled Total Synthesis of Dirchromones and Related 2-Substituted Chromones.

A seven-step total synthesis of the original scaffold of cytotoxic dirchromones involving an unprecedented soft-enolization Baker-Venkataraman rearrangement was designed. The methodology enabled access to naturally occurring dirchromone 1 (21% overall yield) at gram-scale, which was screened for cytotoxicity against 13 cancer cell lines. The scope of the soft-enolization Baker-Venkataraman rearrangement encompasses diversely substituted dirchromones, including flavonoids, 2-styrylchromones, and 2-phenylethylchromones.