1342
Y. L. Aly and E. B. Pedersen
(CDCl3) δ 1.22−1.28 (m, 2 H, H-2ꢁ), 2.74−2.77 (m, 1 H, H-1ꢁ), 2.83−2.85
(m, 1 H, H-1ꢁ), 3.52 (s,1 H, OH), 3.71, 3.72 (2 s, 6 H, 2 × OCH3), 3.77−3.78
(m, 2 H, H-4ꢁ), 4.10−4.13 (m, 1 H, H-3ꢁ), 5.48 (m, 1 H, H-7), 7.18−7.92 (m,
20 H, Harom), 7.82 (s, 1 H, NH); 13 C-NMR (CDCl3) δ 29.66 (C-1ꢁ), 30.34
(C-2ꢁ), 55.65 (OCH3), 59.13 (C-7), 69.42 (C-4ꢁ), 74.98 (C-3ꢁ), 85.91 (C-Ar3),
112.81 (C-11), 113.08, 126.72, 127.80, 128.17, 129.77, 135.80, 144.69, 158.01
(DMT), 125.78, 126.42, 127.47, 127.96, 129.15, 129.86, 129.93, 130.62,
134.51, 142.69 (Carom), 158.51, 163.35 (2 × C = O). HRMS (MALDI) m/z
Calcd for C40H36N2O6 [M+ + Na] 663.2466, found 663.2463.
7-[(S)-3-O-(2-Cyanoethoxy(diisopropylamino)phosphino)-4-(4,4ꢁ-dimethoxytrityl-
oxy)butyl]-7 H-7 a, 9-diazacyclopenta[b]phenanthrene-8,10-dione (7). Compound
6 (0.17 g, 0.27 mmol) was dissolved under nitrogen in dry CH2Cl2
(10 mL). N,N -Diisopropylammonium tetrazolide (97 mg, 0.56 mmol)
was added, followed by dropwise addition of 2-cyanoethyltetraisopropyl-
phosphordiamidite (190 mg, 0.59 mmol). After 30 hours analytical TLC
showed the absence of starting material, and the reaction was quenched
with H2O (1 mL), followed by addition of CH2Cl2 (10 mL). The mixture was
washed with saturated. aqueous. NaHCO3 (2 × 10 mL). The organic phase
was dried over MgSO4, and filtered, and the solvent was evaporated under
reduced pressure. The residue was purified by column chromatography
with 4:5:1 EtOAc-petroleum ether (60–80◦C)-Et3 N to afford compound 7.
1
Yield: 120 mg (53%); yellow foam; H-NMR (CDCl3) δ 0.91–0.93 (m,
2 H, H-2ꢁ), 1.06–1.08 (m, 12 H, 4 × CH3[Pri]), 1.23–1.25 (m, 2 H, H-1ꢁ),
2.03–2.04 (m, 2 H, CH2CN), 3.36–3.41 (m, 2 H, OCH2CH2CN), 3.47−3.54
(m, 2 H, 2 × CH(CH3)2), 3.72 (s, 6 H, 2 × OCH3), 3.74–3.75 (m, 2 H,
H-4ꢁ), 4.10–4.12 (m, 1 H, H-3ꢁ), 5.44 (m, 1 H, H-7), 6.72–7.81 (m, 20 H,
Harom), 8.68 (s, 1 H, NH); 13 C-NMR (CDCl3) δ 14.15 (CH2CN), 19.97
(CH2CH2), 24.31, 24.40, 24.49, 24.55 (4 × CH3), 29.59, 29.85 (C-1ꢁ, C-2ꢁ),
55.10 (OCH3), 59.51 (C-7), 65.24 (C-4ꢁ), 73.51(C-3ꢁ), 86.08 (C-Ar3), 112.78
(C-11), 117.54 (CN), 112.98, 126.57, 127.87, 128.44, 129.91, 135.88, 144.94,
158.03, (DMT), 125.69, 126.40, 127.45, 127.70, 128.60, 129.85, 130.53,
133.55, 136.04, 142.80 (Carom), 158.24, 163.24 (2 × C = O); 31P-NMR
(CDCl3) δ 148.65 (s), 149.03 (s) in ratio 5:4, respectively. HRMS (MALDI)
m/z Calcd for C49H52N4O7P [M+ + K] 879.3288, found 879.3663.
Synthesis and Purification of Oligos
Oligodeoxynucleotides (ODN) were synthesized on an Expedite Nucleic
Acid Synthesis System model 8909 from Applied Biosystems (Foster City,
CA, USA). The phosphoramidite was dissolved in dry MeCN, as a 0.75 M
solution and incorporated into the growing oligonucleotide chain using
elongated coupling times (10 minutes coupling versus 2 minutes for nor-
mal nucleotide couplings). After the completed DNA syntheses, the 5ꢁ-O-
DMT-on oligonucleotides were cleaved off from the solid support (room