Sactibiotics are a unique class of cyclic, broad-spectrum bacteriocins characterized by S-to-α-C thioether linkages between a Cys and a partner residue on the peptide backbone. These bacteriocins were also reported to have high stability to proteolytic degradation and moderate heat and acid treatment due to this unique structural characteristic. However, under physiological pH conditions, the thioether bridges become increasingly susceptible to hydrolysis and oxidation, which can lead to a loss of activity. As such, strategies to increase the in vivo stability of these bacteriocins are of great interest for therapeutic applications. The use of carba-analogues, which involves S-to-CH2 replacement, was found to increase the stability of lanthipeptides with a slight reduction in antimicrobial activity. Herein, we report the synthesis of orthogonally protected α-quaternary diamino diacid (DADA) building blocks for the synthesis of carba-analogues of sactibiotics via solid-phase peptide synthesis (SPPS), using subtilosin A as our model peptide. We achieved the diastereoselective synthesis of 2-benzyl-2,5-diaminoadipic acid precursor using a strategy known as self-regeneration of stereocentres (SRS) to mimic the S-to-α-C thioether linkage between Cys and Phe in subtilosin A. In brief, an oxazolidinone derivative of L– or D–Phe was alkylated to obtain the Phe diamino diacid precursor. Meanwhile, to access the S-to-α-C thioether bridge mimic between Cys and Thr, an oxazoline derivative of L-Thr methyl ester was used instead. The subsequent deprotection of the Phe and Thr diamino diacid precursors, followed by selective installation of orthogonal protecting groups, would give us access to orthogonally protected α-quaternary diamino diacid building blocks for SPPS synthesis of carba-analogues of subtilosin A.