Reaction Steps
A mixture of the cyclopentenyl tosylate 2 (0.25 g, 0.58 mmol), 2-amino-6-chloropurine (0.212 g, 1.25 mmol, 2.2 eq), and K2CO3 (~1 g) was suspended in 2 mL of DMSO and stirred at room temperature for 42 h. The suspension was then poured into CH2Cl2 and washed with dilute NaCl. Evaporation of the CH2Cl2 gave an oil which was further dried under high vacuum to remove residual DMSO. Purification by preparative TLC (silica, 3:2 EtOAc:Hexane) gave two major purine containing products of which the faster moving and predominant was the desired N-9 alkylated purine 18 (0.117 g, 47%), mp 137°-140°; 1H-NMR (CDCl3) δ 1.35 (s, 3H, CH3), 1.46 (s, 3H, CH3), 4.27 (s, 2H, H-6'a,b), 4.61 and 4.62 (2H, PhCH2), 4.67 (d, J=5.3 Hz, 1H, H-2'), 5.10 (br s, 2H, NH2, exchangeable), 5.36 (d, J=5.3 Hz, 1H, H-3'), 5.43 (br s, 1H, H-1'), 5.78 (br s, 1H, H-5'), 7.34 (m, 5H, Ph), 7.65 (s, 1H, H-8); 13C-NMR (CDCl3) δ 25.8 (CH3), 27.2 (CH3), 64.3 (C-1'), 66.2 (C-6'), 72.8 (PhCH2), 83.7 (C-2'), 83.9 (C-3'), 112.4 (methylethylidene C), 122.7 (C-5'), 125.2 (d, J=12.6 Hz, C-5), 127.3 (Ph), 127.5 (Ph), 128.1 (Ph), 128.2 (Ph), 137.6 (Ph), 140.1 (dd, J=210 Hz, J'=4.4 Hz, C-8), 149.2 (C-4'), 151.0 (s, C-6), 153.2 (dd, J=4.7 Hz, J'=3.1 Hz, C-4), 159.1 (s, C-2).
