(2R)-2-(2-(2,5-Difluorophenyl)oxiran-2-yl)propanoic Acid is an intermediate in the synthesis of Isavuconazole-d4 (I777832), labeled Isavuconazole (I777832). It is a new triazole currently undergoing phase III clinical trials. This compound has shown in vitro activity against a large number of clinical important yeasts and molds including Aspergillus spp., Fusarium spp., Scedosporium spp., Candida spp., the Zygomycetes and Cryptococcus spp.