Abstract: | Abstract A protocol for regeneration of key intermediate of aprepitant from its undesired diastereomers is described. This work features the recycling of at least one-third of the undesired isomers (ent-6, 7 and ent-7) to desired isomer 4 as the key early intermediate for the synthesis of aprepitant 1. The key step in our strategy involves diastereomeric salt preparation.![id=](/na101/home/literatum/publisher/tandf/journals/content/tgcl20/2009/tgcl20.v002.i04/17518250903400117/production/images/medium/tgcl_a_440189_o_uf0001.gif) |