(R)-N-((S)-1-Cyclopropylethyl)-2-methylpropane-2-sulfinamide is a chiral intermediate used in the synthesis of enantiomerically pure amines, particularly (S)-1-cyclopropylethylamine. The tert-butanesulfinyl group functions as a removable chiral directing group that ensures high stereochemical integrity during upstream asymmetric transformations, such as nucleophilic additions to derived imines. It can be selectively cleaved under mild acidic conditions (e.g., HCl in methanol) to afford the free chiral amine without racemization. This compound is essential in pharmaceutical synthesis for building complex APIs requiring precise stereocontrol, such as those incorporating the 1-cyclopropylethylamine moiety.