We describe a new general method for the synthesis of medium-sized lactones based on ring-enlargement via a regioselective β-scission of alkoxyl radicals generated by photolysis from the hypoiodites of several catacondensed lactols. The syntheses of 9-membered lactones from 6 5 fused lactols, 10-membered lactones including a naturally occurring lactone, phoracantholide I, from 6 6 or 7 5 fused lactols, and 11-membered lactones from ...