(S)-3,3-dimethyl-2-(2,2,2-trifluoroacetamido)butanoic acid

It is coupled with (1R,2S,5S)-6,6-dimethyl-3-azabicyclohexane-2-carboxylate to form a key intermediate, (1R,2S,5S)-3-((S)-3,3-Dimethyl-2-(2,2,2-trifluoroacetamido)butanoyl)-6,6-dimethyl-3-azabicyclohexane-2-carboxylic acid. (S)-3,3-dimethyl-2-(2,2,2-trifluoroacetamido)butanoic acid acts as a crucial chiral building block in the synthesis of Nirmatrelvir, the active ingredient in Paxlovid.