LETTER
Lipophilic N9-Benzylguanine Derivatives
2873
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(22) N2-Acetyl-N9-(3,5-di-tert-butylbenzyl)guanine (9):
Purification was achieved through flash chromatography
using a CombiFlash® system (regioisomer 9 being more
polar than regioisomer 10) with a gradient of CH2Cl2–
MeOH (100:0→50:50) and subsequent recrystallization in
EtOH–H2O (32%). 1H NMR (400 MHz, DMSO-d6): d = 8.07
(s, 1 H, H-8), 7.31 (s, 1 H, ArH), 7.08 (s, 2 H, ArH), 5.27 (s,
2 H, CH2), 2.16 (s, 3 H, CH3), 1.23 (s, 18 H, 2 × t-Bu).
13C NMR (400 MHz, DMSO-d6): d = 173.5, 155.0, 150.8,
148.7, 147.9, 139.8, 135.9, 121.3, 121.1, 119.9, 46.7, 34.5,
31.1, 23.8. HRMS (ESI+): m/z [MH]+ calcd: 396.2400;
found: 396.2408.
Figure 2 Partial HMBC spectrum of 2. The cross-peak between
NCH2-Ar and C-4 indicates formation of the N9-regioisomer. H-8 ex-
hibits cross-peaks to C-4 and C-5, while the benzylic protons demon-
strate cross-peaks to C-4 and to the aromatic carbons.
(23) N2-Acetyl-N7-(3,5-di-tert-butylbenzyl)guanine (10):
Purification was achieved through flash chromatography
using a CombiFlash® system (regioisomer 9 being more
polar than regioisomer 10) with a gradient of CH2Cl2–
MeOH (100:0→50:50) and subsequent recrystallization in
EtOH–H2O (32%). 1H NMR (400 MHz, CDCl3): d = 7.79 (s,
1 H, H-8), 7.39 (s, 1 H, ArH), 7.23 (s, 2 H, ArH), 5.53 (s,
2 H, CH2), 2.37 (s, 3 H, CH3), 1.29 (s, 18 H, 2 × t-Bu).
13C NMR (400 MHz, CDCl3): d = 173.4, 156.8, 153.5, 151.8,
148.0, 142.8, 134.5, 122.7, 122.0, 112.2, 51.3, 34.9, 31.4,
24.1. HRMS (ESI+): m/z [MH]+ calcd: 396.2400; found:
396.2408.
yields for the coupling reaction of 2-N-acetylguanine with
substituted benzene derivatives and N-deacetylation.
HMBC experiments provided conclusive evidence for the
structure of each regioisomer. Our future plans involve
using these derivatives to investigate the self-assembly of
G-quartet structures and examine low-temperature gua-
nine oxidation intermediates.
References and Notes
(24) N9-(3,5-Di-tert-butylbenzyl)guanine (1): Purification
was achieved through flash chromatography using a
CombiFlash® system with a gradient of CH2Cl2–MeOH
(100:0→50:50) and subsequent recrystallization in EtOH–
H2O (71%). 1H NMR (400 MHz, DMSO-d6): d = 10.67 (s,
1 H, NH), 7.76 (s, 1 H, H-8), 7.28 (s, 1 H, ArH), 7.11 (s, 2 H,
ArH), 6.48 (s, 2 H, NH2), 5.13 (s, 2 H, CH2), 1.22 (s, 18 H,
2 × t-Bu). 13C NMR (400 MHz, DMSO-d6): d = 157.1,
153.8, 151.4, 150.8, 137.7, 136.5, 121.5, 121.2, 116.5, 46.5,
34.6, 31.3. HRMS (ESI+): m/z [MH]+ calcd: 354.2294;
found: 354.2294.
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(25) N2-Acetyl-N9-[3,5-bis(tert-butyldimethylsilyloxy)-
benzyl]guanine (11): Purification was achieved through
flash chromatography using a CombiFlash® system
(regioisomer 11 being more polar than regioisomer 12) with
a gradient of CH2Cl2–MeOH (100:0→50:50) and subse-
quent recrystallization in EtOH–H2O (33%). 1H NMR (400
MHz, CDCl3): d = 7.64 (s, 1 H, H-8), 6.27 (s, 3 H, ArH),
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Synlett 2010, No. 19, 2871–2874 © Thieme Stuttgart · New York