Reaction Steps
To a slurry of N-[3-({3-[(3-{(3β)-cholest-5-en-3-yl [(2-nitrophenyl)sulfonyl]amino}propyl)amino]-3-oxopropyl}amino)-3-oxopropyl]-6-(7-nitrobenzofurazan-4-ylamino)hexanamide (24, 29 mg, 0.028 mmol) and K2CO3 (76 mg, 0.552 mmol) in N,N-dimethylformamide (6 mL) and tetrahydrofuran (2 mL) was added thiophenol (40 μL, 0.389 mmol). After 18 h at 23° C., the suspension was filtered and solvent removed in vacuo. Purification by preparative reverse-phase HPLC (gradient: 59.9% MeCN, 40% H2O, and 0.1% TFA to 99.9% MeCN, 0% H2O, and 0.1% TFA over 14 min; retention time=10.6 min) afforded 6 (15 mg, 52%) mp 170-171° C.; 1H NMR (500 MHz, CDCl3) δ 9.54 (br s, 1H), 8.68 (br s, 1H), 8.50 (d, J=8.4 Hz, 1H), 8.07 (t, J=5.35, 1H), 7.92 (t, J=5.4 Hz, 1H), 7.80 (t, J=5.3 Hz, 1H), 6.40 (d, J=8.9 Hz, 1H), 5.36 (m, 1H), 3.43 (m, 1H), 3.24-3.17 (m, 4H), 3.10 (m, 2H), 2.88 (br s, 3H), 2.35 (d, J=7.2 Hz, 2H), 2.23 (t, J=6.9 Hz, 2H), 2.18 (t, J=7.1 Hz, 2H), 2.04 (t, J=7.2 Hz, 2H), 1.94-0.96 (m, 35H), 0.93 (s, 3H), 0.86 (d, J=6.2 Hz, 3H), 0.84 (d, J=2.1 Hz, 3H), 0.82 (d, J=2.1 Hz, 3H), 0.62 (s, 3H); 13C NMR (125.8 MHz, DMSO d6) δ 171.9, 170.8, 170.3, 145.1, 144.4, 144.2, 138.6, 137.9 122.3, 120.5, 99.1, 56.6, 56.1, 55.5, 49.3 (×2), 45.5, 43.3, 41.8 (×2), 41.5, 36.4, 36.2, 35.6 (×2), 35.5 (×2), 35.3 (×2), 35.2, 35.1, 34.3, 31.2, 27.7, 27.4, 27.3, 26.2, 26.0, 24.9, 24.3, 23.8, 23.2, 22.6, 22.4, 20.5, 18.8, 18.5, 11.6; IR (film) νmax 3173, 3075, 2919, 2848, 1634, 1538, 1331 cm−1; CI m/z 861.5965 (MH+, C48H77N8O6 requires 861.5966).
