<A NAME="RG12704ST-5E">5e</A>
Typical Procedure for the Coupling: 3′,5′-di-TBDMS-dU-5-I (66.5 mg, 114 µmol) and CuI (8.8 mg, 45.6 µmol) were dissolved
in anhyd DMF (4 mL). Then Et3N (60 µL) and 6 (70 mg, 80 µmol) were added in DMF (2 mL), and the mixture was degassed by purging
with Ar in the dark. After 10 min, Pd(PPh3)4 (26.4 mg, 22.8 µmol) was added in one portion and the mixture stirred at r.t. After
48 h, the mixture was diluted with EtOAc (150 mL), and the organic phase was washed
with brine (3 × 30 mL) and H2O (2 × 30 mL). The organic phase was dried (Na2SO3) and evaporated; some residual DMF was removed in vacuo. Column chromatography on
silica (CH2Cl2-EtOAc 5:1 to CH2Cl2-EtOAc-MeOH 5:1:0.01) and crystallisation from CH2Cl2-hexane yielded 82 mg of 8 (62 µmol, 78%).
Representative Analytical Data. Compound 8: 1H NMR (400 MHz, CDCl3): δ = 8.95 (s, 2 H, β-pyrrole), 8.94 (s, 2 H, β-pyrrole), 8.92 (s, 2 H, β-pyrrole),
8.91 (s, 2 H, β-pyrrole), 8.43 (d, J = 8 Hz, 6 H, Ph-H), 8.31 (d, J = 8 Hz, 6 H, Ph-H), 8.17 (d, J = 8 Hz, 2 H, Ph-H), 8.03 (s, 1 H, N-H), 7.82 (d, J = 8 Hz, 2 H, Ph-H), 7.72 [s, 1 H, C(6)-H], 6.15 [t, J = 6 Hz, 1 H, C(1′)-H], 4.39 [m, 1 H, C(3′)-H], 4.10 (s, 9 H, COCH3), 3.85 [br s, 1 H, C(4′)-H], 3.82 [d, J = 12 Hz, 1 H, C(5′)-H], 3.73 [d, J = 12 Hz, 1 H, C(5′)-H], 2.32 [m, 1 H, C(2′)-H], 2.03 [m, 1 H, C(2′)-H], 0.97 (s,
9 H, Sit-Bu), 0.91 (s, 9 H, Sit-Bu), 0.23, 0.19, 0.10, 0.09 [4 × s, 12 H, Si-(CH3)2] ppm. MALDI-TOF MS: m/z calcd for C73H72N6O11Si2Zn: 1330.95. Found: 1330.59.
Compound 5: 1H NMR (400 MHz, CD3OD-CDCl3 9:1): δ = 10.09 (s, 1 H, N-H), 8.48 [s, 1 H, C(6)-H], 8.02 (m, 3 H, Ph-H), 7.89 (d,
J = 8 Hz, 2 H, Ph-H), 7.78 (t, J = 8 Hz, 1 H, Ph-H), 7.71 (t, J = 9 Hz, 1 H, Ph-H), 7.57 (s, 2 H, Ph-H), 6.30 [t, J = 6 Hz, C(1′)-H], 4.54 [br s, 1 H, C(5′)-OH], 4.29 (t, J = 8 Hz, 8 H, CH2-CH2CO2CH3), 3.97 [d, J = 3 Hz, 1 H, C(4′)-H], 3.88 [d, J = 11 Hz, 1 H, C(5′)-H], 3.77 [d, J = 11 Hz, 1 H, C(5′)-H], 3.63 (s, 12 H, CH2-CH2CO2CH3), 3.14 (t, J = 8 Hz, 8 H, CH2-CH2CO2CH3), 2.46 (s, 6 H, CH3), 2.42 (s, 6 H, CH3), 0.91 (s, 9 H, Sit-Bu), 0.13 [s, 6 H, Si-(CH3)2] ppm. MALDI-TOF MS: m/z calcd for C69H76N6O13SiZn: 1290.85. Found: 1290.93.
It should be noted that Sephadex column chromatography (when necessary) was performed
in a column of 2 m length, containing approx. 150 g of Sephadex. The mobile phase
was allowed to run at a rate of a drop per second.
