Reaktionsschritte
N4,5'-O-dibenzoyl-2'-fluoro-3'-(4-methoxytrityl)amino-2',3'-dideoxycytidine 14 was prepared as follows: To 0.9 g (2.0 mmol) of 13 in 25 mL anhydrous pyridine was added 0.86 g (2.8 mmol) 4-methoxytrityl chloride, and the mixture stirred overnight. The reaction was quenched with 0.5 mL H2O and concentrated in vacuo. CH2Cl2 (50 mL) was added and washed with 50 mL saturated aqueous NaHCO3 and with water (2×50 mL). The solvent was removed in vacuo, replaced with 10 mL CH2Cl2, and pipetted into 80 mL rapidly stirred 1/1 hexane/ether. After further stirring for 2 h, the product was collected by filtration and dried under vacuum, giving 1.3 g (88% yield) of product as a white powder. Mass-spectrometry, FAB+, M+H+, calculated: 725.2775, observed: 725.2761. 1H NMR δ 8.59 (br s, 1H), 8.07 (br d, J=5.7 Hz, 1H), 7.89 (br d, J=7 Hz, 2H), 7.83 (dd, J=1.3, 6.7 Hz, 2H), 7.68 (dd, J=7.4, 7.4 Hz, 2H), 7.5-7.6 (m, 8H), 7.43 (dd, J=2.1, 6.9 Hz, 2H), 7.1-7.3 (mm, 7H), 6.71 (d, J=8.9 Hz, 2H), 5.80 (d, J=15.4 Hz, 1H), 5.03 (dd, J=2.0, 13.0 Hz, 1H), 4.98 (dd, J=2.3;, 13.1 Hz, 1H),4.41 (brd,J=10.5 Hz, 1H),3.63 (s,3H),3.36(dddd,J=3.1, 11.1, 11.1, 25.7 Hz, 1H), 2.84 (dd, J=3.1, 49.9 Hz, 1H), 2.52 (dd, J=2.7, 11.5 Hz, 1H); 19F NMR δ -196.3 (m).
