Novel base-induced [1,2]-acyl shift of allylic esters of cyclopropanecarboxylic acids.

The cylindramides are marine natural products containing a tetramic acid lactam and an interesting bicyclo[3.3.0] ring system.1 Cylindramide 1 has shown strong cytotoxicity against cancer cell lines (IC50 of 0.8 mg/mL against B16 melanoma cells) while several other natural products with structures similar to that of cylindramide have interesting biological properties.2-5 Our synthetic studies on the cylindramides focused on the use of a novel, tandem radical rearrangement to synthesize the bicyclo[3.3.0]octane ring system of the natural product.