Based on early literature findings showing that ABBs could undergo diastereospecific opening, it was hypothesized that enantiopure 2-substituted ABBs may be amenable to stereospecific openings (strain-release) with a variety of nucleophiles. 7 These ABBs were thus targeted for synthesis to explore their downstream functionalization with nucleophiles of varying pKas. For the purposes of this study, a suitably protected 2-hydroxymethyl substituent was chosen (vide infra). With this goal in mind, a scalable, enantiocontrolled approach to procure all four diastereomers of 3,4-dibromo-1-(tert-butoxy)butan-2-amine (ABB precursor) was developed (Figure ). The simple four-step sequence commencing from 2-tert-butoxy-ethanol (ca. $0.25/g) involved: (1) oxidation to form the corresponding aldehyde (IBX), (2) reaction with either (R) or (S) Ellman's sulfinamides to afford the enantiopure tert-butanesulfinyl imines, (3) stereoselective 1,2-addition with vinylmagnesium bromide, and (4) addition of Br2 followed by column chromatography to afford all the corresponding chiral ABB precursors. An alternative approach to access these ABB precursors using asymmetric p-allyl substitution was also developed (See SI for details).