Fmoc-Asp(OtBu)-OH-d 3 (4-tert-Butyl N-(fluoren-9-ylmethoxycarbonyl)-L-aspartate-d 3 )is deuterium labeled Fmoc-Asp(OtBu)-OH. Fmoc-Asp(OtBu)-OH (4-tert-Butyl N-(fluoren-9-ylmethoxycarbonyl)-L-aspartate) is a aspartate derivative containing amine protecting group Fmoc. Fmoc-Asp(OtBu)-OH can be used for peptide synthesis.