Introduction 1 2 1 2A 2B 3 3 1 3 2A 2B 4 2B 5 6 5 7 8 9 2B 10 11 2B 10 12 1 2A 3 2B 13 2B 1 1 2 1 14 15 3 2B 3 16 4 2B 3, 17 1 Fig. 1 i 2B  1 3 1 3 18 22 2B 2B 21 3 N 6 2B N 6 5 6 7 14 2B 2 Fig. 2 Structures of designed compounds  Chemistry 5–14 1 2 5 23 15 5 5a 5 5a 1 2 5a 2 2 5 2 Scheme 1 a b 2 3 3  Scheme 2 Reagents: i: CDI, dry THF, reflux  6 16 5 17 17a 24 1 17 17a 3 24 1 17 6 24 1 7–14 5 6 18–22 25 2 Results and discussion 1 2A 3 2B 3 N 6 1 3 N 2A 3 2B i 50 i 26 1 Table 1 5–14  a 3 1 b 3 2A c i 2B d 3 3 5–14 1 2A 3 2B i N 6 5 6 7–14 1 2B N 6 6 i 2B N 6 N 6 6 1 2A 3 2B 5 N 6 8 7 1 2B 3 N 6 1 3 2B 9 i 1 i 2B i 3 10 i 1 i 2B i 3 12 i 1 i 2B i 3 13 i 1 i 2B i 3 2A 2A 5 7 9 12 6 8 10 13 N 6 2A 6 i 2A N 6 2A 27 32 N 6 1 3 9 i 1 11 i 3 5 i 1 i 3 9 11 para 1 3 12 14 Conclusions 2B N 6 1 3 2A 2B 1 3 Experimental section Chemistry General: 1 J 2 5 and 7-propyladenine 5a 15 2 3 3 5 23 5a 3 5 1 d 6 J 3 CH 2 3 J 2 2 5 5 5 5a 1 d 6 J 3 CH 2 3 J 2 2 5 5 5 17 and 2,6-dichloro-7-propyl-9H-purine 17a 16 2 3 6 12 17 17a 24 17 1 d 6 J 2 CH 3 CH 2 3 J 2 8 8 2 4 17a 1 d 6 J 2 CH 3 CH 2 3 J 2 8 8 2 4 6 17 3 6 24 1 d 6 J 2 CH 3 CH 2 3 J 2 2 8 10 5 N 6 7 14 18–22 5 6 7–14 7 3 1 d 6 J 2 CH 3 CH 2 3 2 J 2 J J 16 16 5 8 3 6 12 1 d 6 J 2 CH 3 CH 2 3 2 J 2 J J 16 15 5 9 3 1 d 6 J 2 CH 3 CH 2 3 2 J 2 2 J J J J 23 22 5 2 10 3 6 12 1 d 6 J 2 CH 3 CH 2 3 2 J 2 2 J J J J 23 21 5 2 11 3 6 12 1 d 6 J 2 CH 3 CH 2 3 CH 3 2 J 2 2 J 24 25 5 2 12 3 1 d 6 J 2 CH 3 CH 2 3 2 J 2 2 J J 23 23 5 2 13 3 1 d 6 J 2 CH 3 CH 2 3 2 J 2 2 J J 23 22 5 2 14 3 1 d 6 J 2 CH 3 CH 2 3 3 2 J 2 2 J J J J 24 24 5 3 Biology 26 g g 1 3 3 2A 3 3 3 i 33 2B 50 i 34