## 2 Materials and Methods
### Synthesis  
Thione derivatives of caffeine and gramine (1-((1H-indol-3-yl)methyl)-1,3-dihydro-2H-benzo[d]imidazole-2-thione and 1,3,7-trimethyl-8-sulfanylidene-9H-purine-2,6-dione) were synthesized according to the procedure of [37] and [38], respectively. The bromoacetate compounds were obtained according to [39]. A typical procedure for the synthesis of compounds **1-10** is reported to the following. In a round-bottom flask, 0.15 mmol of bromoacetate (methyl lithocholate, methyl deoxycholate, methyl cholate, cholesteryl, dihydrocholesterol) was dissolved in 2 mL of DMF (dimethylformamide). Two eq (0.30 mmol) of K\({}_{2}\)CO\({}_{3}\) (44 mg) and 0.15 mmol of gramine or caffeine derivatives were added and stirred at room temperature for 2-3 h. Five mL of water was added to the reaction mixture, and the reaction mixture was transferred to a separatory funnel. It was extracted with ethyl acetate. It was washed with brine and water. The organic layer was dried over anhydrous Na\({}_{2}\)SO\({}_{4}\). The resulting oil was purified on a chromatography column using chloroform as eluent. 3\(\beta\)-[2-thio-(1-((1H-indol-3-yl)methyl)-1,3-dihydro-2H-benzo[d]imidazole]acetate-cholest-5-ene (1)  
Oil, 86%, \({}^{1}\)H NMR (400 MHz, CDCl\({}_{3}\)) \(\delta\): 8.31 (s, 1H, NH), 7.65-7.56 (m, 2H, aromatic), 7.36-7.30 (m, 2H, aromatic), 7.20-7.07 (m, 4H, aromatic), 6.99 (d, \(J\) = 2.5 Hz, 1H, aromatic), 5.47 (s, 2H, CH\({}_{2}\)-10\({}^{\prime}\)), 5.33 (d, \(J\) = 5.0 Hz, 1H, 6-H), 4.69-4.61 (m 1H, 3\(\alpha\)-H), 4.19 (s, 2H, CH\({}_{2}\)-29), 0.99 (s, 3H, CH\({}_{3}\)-19), 0.91 (d, \(J\) = 6.5 Hz, 3H, CH\({}_{3}\)-21), 0.86 (dd, \(J\) = 6.6, 1.8 Hz, 6H, CH\({}_{3}\)-26,27), 0.67 (s, 3H, CH\({}_{3}\)-18). \({}^{13}\)C NMR (101 MHz, CDCl\({}_{3}\)) \(\delta\): 168.16 (C-28), 150.48 (C-2\({}^{\prime\prime}\)), 143.44 (C-8\({}^{\prime\prime}\)), 139.43 (C-5), 136.47 (C-7\({}^{\prime\prime}\)), 136.34 (C-9\({}^{\prime\prime}\)), 125.96 (C-8\({}^{\prime}\)), 123.37 (C-5\({}^{\prime\prime}\)), 122.82 (C-6), 122.55 (C-4\({}^{\prime\prime}\)), 122.02 (C-2\({}^{\prime}\)), 121.87 (C-6\({}^{\prime}\)), 120.10 (C-5\({}^{\prime}\)), 118.60 (C-3\({}^{\prime\prime}\)), 118.39 (C-4\({}^{\prime}\)), 111.43 (C-3\({}^{\prime}\)), 110.76 (C-7\({}^{\prime}\)), 109.44 (C-6\({}^{\prime\prime}\)), 75.77 (C-3), 56.68, 56.16, 50.00, 42.31, 40.32, 39.73, 39.52, 37.89, 36.91, 36.56, 36.19, 35.77, 35.24, 31.89, 31.85, 29.68, 28.20, 28.00, 27.58, 24.27, 23.83, 22.80, 22.55, 21.02, 19.28 (C-19), 18.72 (C-21), 11.85 (C-18). FT-IR (KBr) \(\
u_{\rm max}\) (cm\({}^{-1}\)): 3410, 2935, 2867, 1732, 1447, 1379, 1349, 1319, 1296, 1241, 1168. ESIMS (MeOH): C\({}_{45}\)H\({}_{98}\)N\({}_{3}\)O\({}_{5}\)\(m/z\) 707 [M+H]\({}^{+}\), 729 [M+Na]\({}^{+}\), 745 [M+K]\({}^{+}\). 3\(\beta\)-[2-thio-(1-((1H-indol-3-yl)methyl)-1,3-dihydro-2H-benzo[d]imidazole]acetate-5\(\beta\)-cholestan (2)  
Solid, m.p. 187.5-189.5 \({}^{\circ}\)C, 76%, \({}^{1}\)H NMR (400 MHz CDCl\({}_{3}\)) \(\delta\): 8.20 (s, 1H, NH), 7.64-7.60 (m, 2H, aromatic), 7.40-7.29 (m, 2H, aromatic), 7.22-7.10 (m, 4H, aromatic), 7.03 (d, \(J\) = 2.5 Hz, 1H, aromatic), 5.50 (s, 2H, CH\({}_{2}\)-10\({}^{\prime}\)), 4.77-4.69 (m, 1H, 3\(\alpha\)-H), 4.18 (s, 2H, CH\({}_{2}\)-29), 0.89 (d, \(J\) = 6.5 Hz, 3H, CH\({}_{3}\)-21), 0.86 (dd, \(J\) = 6.6, 1.9 Hz, 6H, CH\({}_{3}\)-26,27), 0.79 (s, 3H, CH\({}_{3}\)-19), 0.64 (s, 3H, CH\({}_{3}\)-18).