(1R,2R)-2-(2,3-Dihydro-4-benzofuranyl)-cyclopropanecarboxylic Acid Ethyl Ester is an intermediate in the synthesis of tasimelteon (T007740). Tasimelteon is a novel drug, used in the treatment of non-24 hour sleep-wake disorder. It helps to correct the circadian rhythm disorder often seen in patients who are visually impaired.