## 2 Materials and Methods
### Synthesis
\({}^{13}\)C NMR (101 MHz, CDCl\({}_{3}\)) \(\delta\): 168.28 (C-28), 150.49 (C-2\({}^{\prime\prime}\)), 143.43 (C-8\({}^{\prime\prime}\)), 136.41 (C-7\({}^{\prime\prime}\)), 136.27 (C-9\({}^{\prime}\)), 125.90 (C-8\({}^{\prime}\)), 123.30 (C-5\({}^{\prime\prime}\)), 122.58 (C-4\({}^{\prime\prime}\)), 121.98 (C-2\({}^{\prime}\)), 121.83 (C-6\({}^{\prime}\)), 120.11 (C-5\({}^{\prime}\)), 118.63 (C-3\({}^{\prime\prime}\)), 118.39 (C-4\({}^{\prime}\)), 111.39 (C-3\({}^{\prime}\)), 110.83 (C-7\({}^{\prime}\)), 109.41 (C-6\({}^{\prime\prime}\)), 75.59 (C-3), 56.37, 56.22, 54.13, 44.58, 42.55, 40.29, 39.93, 39.49, 36.65,36.13, 35.77, 35.42, 35.39, 35.27, 33.76, 31.93, 29.69, 28.52, 28.22, 27.99, 27.26, 24.18, 23.81, 22.81, 22.55, 21.16 (C-21), 18.64 (C-19), 12.04 (C-18). FT-IR (KBr) \(\gamma_{\rm max}\) (cm\({}^{-1}\)): 3418, 2929, 2865, 1737, 1731, 1716, 1447, 1378, 1281, 1172. ESIMS (MeOH): C\({}_{45}\)H\({}_{61}\)N\({}_{3}\)O\({}_{2}\)S \(m/z\) 710 [M+H]\({}^{+}\), 731 [M+Na]\({}^{+}\), 747 [M+K]\({}^{+}\). 3\(\beta\)-[8-thio-1,3,7-trimethyl-1H-purine-2,6(3H,7H)-dione]acetate-cholest-5-ene (**3**)  
Solid, m.p. 181-182 \({}^{\circ}\)C, 82%, \({}^{1}\)H NMR (401 MHz, CDCl\({}_{3}\)) 8: 5.37 (d, \(J\) = 5.1 Hz, 1H, 6-H), 4.71-4.62 (m, 1H, 3\(\alpha\)-H), 4.02 (s, 2H, CH\({}_{2}\)-29), 3.90 (s, 3H, CH\({}_{3}\)-14\({}^{\prime}\)), 3.53 (s, 3H, CH\({}_{3}\)-12\({}^{\prime}\)), 3.39 (s, 3H, CH\({}_{3}\)-10\({}^{\prime}\)), 1.01 (s, 3H, CH\({}_{3}\)-19), 0.91 (d, \(J\) = 6.5 Hz, 3H, CH\({}_{3}\)-21), 0.86 (dd, \(J\) = 6.6, 1.9 Hz, 6H, CH\({}_{3}\)-26.27), 0.68 (s, 3H, CH\({}_{3}\)-18). \({}^{13}\)C NMR (101 MHz, CDCl\({}_{3}\)) 8: 167.54 (C-28), 154.61 (C-6\({}^{\prime}\)), 151.46 (C-2\({}^{\prime}\)), 149.32 (C-4\({}^{\prime}\)), 148.28 (C-8\({}^{\prime}\)), 139.11 (C-5), 123.12 (C-6), 108.88 (C-5\({}^{\prime}\)), 76.00 (C-3), 56.63, 56.09, 49.94, 42.28, 39.66, 39.48, 37.94, 36.84, 36.53, 36.15, 35.76, 34.91, 32.35 (C-14\({}^{\prime}\)), 31.85, 31.79, 29.70 (C-12\({}^{\prime}\)), 28.19 (C-10\({}^{\prime}\)), 27.99, 27.86, 27.63, 24.25, 23.80, 22.80, 22.54, 20.99, 19.26 (C-19), 18.69 (C-21), 11.83 (C-18). FT-IR (KBr) \(\gamma_{\rm max}\) (cm\({}^{-1}\)): 2946, 2867, 1733, 1703, 1659, 1538, 1454, 1367, 1176. ESI-MS (MeOH): C\({}_{37}\)H\({}_{56}\)N\({}_{4}\)O\({}_{4}\)S \(m/z\) 675 [M+Na]\({}^{+}\). 3\(\beta\)-[8-thio-1,3,7-trimethyl-1H-purine-2,6(3H,7H)-dione]acetate-5\(\beta\)-cholestan (**4**)  
Oil, 91%,\({}^{1}\)H NMR (401 MHz, CDCl\({}_{3}\)) \(\delta\): 4.80-4.71 (m, 1H, 3\(\alpha\)-H), 4.01 (s, 2H, CH\({}_{2}\)-29), 3.89 (s, 3H, CH\({}_{3}\)-14\({}^{\prime}\)), 3.52 (s, 3H, CH\({}_{3}\)-12\({}^{\prime}\)), 3.39 (s, 3H, CH\({}_{3}\)-10\({}^{\prime}\)), 0.89 (d, \(J\) = 6.5 Hz, 3H, 10\({}^{\prime}\)), 0.86 (dd, \(J\) = 6.6, 1.9 Hz, 6H, CH\({}_{3}\)-26.27), 0.81 (s, 3H, CH\({}_{3}\)-19), 0.64 (s, 3H, CH\({}_{3}\)-18). \({}^{13}\)C NMR (101 MHz, CDCl\({}_{3}\)) \(\delta\): 167.6 (C-28), 154.61 (C-6\({}^{\prime}\)), 151.46 (C-2\({}^{\prime}\)), 149.31 (C-4\({}^{\prime}\)), 148.30 (C-8\({}^{\prime}\)), 108.88 (C-5\({}^{\prime}\)), 75.83 (C-3), 56.38, 56.26, 54.16, 44.59, 42.57, 39.94, 39.49, 36.64, 36.15, 35.76, 35.44, 35.42, 35.00, 33.88, 32.35 (C-14\({}^{\prime}\)), 31.91, 29.69 (C-12\({}^{\prime}\)), 28.57, 28.20 (C-10\({}^{\prime}\)), 27.98, 27.84, 27.34, 24.17, 23.81, 22.78, 22.53, 21.18 (C-19), 18.65 (C-21), 12.04 (C-18). FT-IR (KBr) \(\gamma_{\rm max}\)(cm\({}^{-1}\)): 2935, 2867, 1732, 1704, 1659, 1538, 1452, 1367, 1179. ESI-MS (MeOH): C\({}_{37}\)H\({}_{58}\)N\({}_{4}\)O\({}_{4}\)S \(m/z\) 678 [M+Na]\({}^{+}\), 694 [M+K]\({}^{+}\).