Reaction Steps
Cbz-Val-Phe-VS-Ph was treated with butyllithium and tert-butylhydroperoxide in freshly distilled THF as described with Cbz-Leu-Phe-VS-Ph above to give Cbz-Val-Phe-AS-Ph as a white powder, yield 21%. 1H-NMR (CDCl3) δ 0.70-0.85 (2d, 6H, Val-CH3), 2.1 (m, 1H, Val-CH), 3.80 (d, 2H, CH2-Phe), 3.95 (m, 3H, CH2—SO2 and α-H), 4.90 (t, 1H, CH═), 5.12 (m, 3H, NH and Cbz), 7.1-7.4 (m, 10H, 2×Ph), 7.55 (t, 2H, SO2-Ph), 7.65 (t, 1H, SO2-Ph), 7.91 (d, 2H, SO2-Ph), 8.42 (b, 1H, NH). 13C NMR (300 MHz, CDCl3) δ 172.1, 156.3, 144.4, 140.8, 135.7, 134.2, 133.6, 131.2, 129.5, 129.4×2, 129.3, 128.8×2, 128.7, 128.6, 128.4, 128.3, 127.8, 127.3, 126.9, 106.3, 67.6, 56.0, 55.6, 41.7, 22.0, 21.0, 18.4. MS (FAB+) m/z 521 (M+1, 100%). Anal. calcd. for C29H32N2O5S.1/10 H2O: C, 66.67; H, 6.21; N, 5.36. Found: C, 66.31; H, 6.23; N, 5.26.
