All commercially available reagents were used without further purification. All reactions, unless otherwise indicated, were carried out in flame-dried flasks under argon atmosphere with anhydrous solvents. FTIR spectra were recorded using a Perkin-Elmer Spectrum One FT-IR. 1 H, data were in accordance with the literature. (S)-N-((S)-1-cyanopent-4-en-1-yl)-2-methylpropane-2-sulfinamide (16) Imine 15 (462 mg, 1 eq) was dissolved in DCM (24 mL), and Gd(OTf)3 (298 mg, 0.2 eq) and TMSCN (489 mg, 0.62 mL, 2 eq) were added. The reaction stirred for 48h at room temperature and was quenched with saturated NaHCO3. The product was extracted with DCM, and the combined organic layers were washed with brine, dried over Na2SO4, and concentrated in vacuo to give the crude product as a brown oil, which was purified by flash chromatography on a silica gel column (eluent 70:30 hexanes-EtOAc) to give the product as a yellow oil (318 mg, 60% (43 mg, 0.1 eq) and water (0.9 mL) were added, turning the reaction light blue. Benzylamine (37 mg, 0.2 eq) was added, turning the mixture dark blue. The mixture stirred at room temperature for 10 minutes, and was then cooled to 0°C. The sulfinylimine 15a (320 mg, 1 eq) in toluene (2.1 mL) was added, followed by B2pin2 (651 mg, 1.5 eq), and the reaction mixture turned turquoise. The reaction was kept at 0°C for 15 minutes, then was warmed to room temperature and stirred overnight, after which the reaction turned dark brown. The mixture was diluted with ethyl acetate and quenched with saturated NaHCO3. The biphasic mixture stirred for 30 minutes. The product was then extracted from the aqueous layer with ethyl acetate, and the organic layer was washed with saturated NH4Cl, saturated NaHCO3 (copiously) and brine, dried over Na2SO4, and concentrated in vacuo to give the crude product as a brown oil, which was clarified with charcoal to give a clear oil (385 mg, 71%). Rf = streaks on regular silica; IR (film) cm General peptide coupling procedure A. The protected amino acid (1 eq) was suspended in DCM (0.1 M), and HOBt•H2O (1.2 eq) was added, followed by EDC•HCl (1.2 eq). The reaction stirred at 0℃ for 1h. The amine salt (1 eq) was then added, followed by Et3N (3 eq). The reaction stirred at 0℃ for 1h, then at room temperature overnight. Water was added, and the product was extracted with DCM. The combined organic layers were washed with saturated NH4Cl, saturated NaHCO3, and brine, dried over Na2SO4, filtered, and concentrated in vacuo to give the crude product. The crude material was purified by flash chromatography on a silica gel column to give the corresponding dipeptide.