Synthesis of Fmoc-Protected Alkyne Amino Acids

Fmoc-Propargylamine and Fmoc-Mba (Fmoc-2-methyl-3-butyn-2-amine) were prepared accordingly as described before [18 (link)]. The structures of both compounds, as well as the spectra of their ¹H and ¹³C NMR analysis, can be found in the Supplementary Materials (Figures S5 and S6). ¹H and ¹³C NMR spectra were recorded on a Bruker 500 MHz spectrometer (Bruker Corporation, Billerica, MA, USA).
Fmoc-Propargylamine (5): 1H NMR (DMSO-d6, 500 MHz) δ 7.89 (2H, d, J = 7.5 Hz, Fmoc H4 and H5), 7.78 (1H, t, J = 5.5 Hz, NH), 7.69 (2H, d, J = 7.0 Hz, Fmoc H1 and H8), 7.41 (2H, td, J = 7.5, 0.5 Hz, Fmoc H3 and H6), 7.33 (2H, td, J = 7.5, 1.0 Hz, Fmoc H2 and H7), 4.32 (2H, d, J = 7.0 Hz, Fmoc CH2), 4.22 (1H, t, J = 6.7 Hz, Fmoc H9), 3.78 (2H, dd, J = 6.0, 2.5 Hz, H3), 3.11 (1H, t, J = 2.5 Hz, H1);
13C NMR (DMSO-d6, 125 MHz) δ 155.92 (C), 143.81 (C), 143.81 (C), 140.73 (C), 140.73 (C), 127.64 (CH), 127.64 (CH), 127.08 (CH), 127.08 (CH), 125.15 (CH), 125.15 (CH), 120.13 (CH), 120.13 (CH), 81.38 (C), 73.05 (CH), 65.67 (CH2), 46.61 (CH), 29.78 (CH2).
Fmoc-Mba (6): 1H NMR (DMSO-d6, 500 MHz) δ 7.89 (2H, d, J = 7.5 Hz, Fmoc H4 and H5), 7.73 (2H, d, J = 7.5 Hz, Fmoc H1 and H8), 7.58 (1H, s, NH), 7.41 (2H, td, J = 7.5, 0.5 Hz, Fmoc H3 and H6), 7.33 (2H, td, J = 7.5, 1.0 Hz, Fmoc H2 and H7), 4.27 (2H, d, J = 5.5 Hz, Fmoc CH2), 4.20 (1H, t, J = 6.5 Hz, Fmoc H9), 3.07 (1H, s, H1), 1.47 (6H, s, Me groups);
13C NMR (DMSO-d6, 125 MHz) δ 154.37 (C), 143.90 (C), 143.90 (C), 140.72 (C), 140.72 (C), 127.62 (CH), 127.62 (CH), 127.06 (CH), 127.06 (CH), 125.28 (CH), 125.28 (CH), 120.10 (CH), 120.10 (CH), 88.10 (C), 88.10 (C), 70.77 (CH), 65.19 (CH2), 46.68 (CH3), 46.13 (CH3), 29.14 (C).