Chlorotrimethylsilane → 6-Azauridine

Participants

Reaction Conditions

Reaction Steps

A mixture of 15 mmol (2.25 g) of dry D-ribose and 5 mmol (0.565 g) of 6-azauracil is silylated for 2 hours with 15 ml of HMDS and 0.1 ml of trimethylchlorosilane in 30 ml of boiling absolute acetonitrile. After concentrating by evaporation in vacuo, the residue is kept at 80°/1 mm for 2 hours and then dissolved in 40 ml of boiling absolute acetonitrile; 5.5 mmol (0.99 ml) of trimethylsilyl triflate in 10 ml of acetonitrile are then added at 80° C. and within the space of 45 minutes. After the mixture had been kept at 80° C. for 7 hours, 20 ml of a saturated, aqueous solution of NaHCO3 are added at 24° C. and the resulting dark-colored mixture is stirred at 24° C. for 4 hours. Following concentration, the dark-colored residue is extracted with 3×100 ml of boiling methanol and the extracts are concentrated. The residue is dissolved in approx. 10 ml of water and absorbed to approx. 20 g of SiO2, which is loaded onto a column of 200 g of SiO2 (previously treated for 4 hours with 25% NH3 (9:1) until a clear filtrate is obtained). Elution with ethanol/25% NH3 (9:1) first leads to 675 ml of eluate containing quantities of sugar and also traces of 6-azauracil. The following 650 ml yield 0.84 g (68.3%) of slightly colored crude 6-azauridine. The latter is treated in water with active charcoal and then crystallized from ethanol, yielding pure crystalline 6-azauridine (melting point 159°-161° C.).

Provenance & Evidence