Trimethylsilyl triflate → 1-(2,3,4-Tri-O-benzoyl-beta-D-ribopyranosyl)-5-(2-phtalimidoethyl)uracil

Participants

Reaction Conditions

Reaction Steps

7.00 g (24 mmol) of 32 and 13.6 g (24 mmol) of 33 were suspended in 120 ml of acetonitrile in a 250 ml three-necked flask, equipped with an argon lead-in, internal thermometer and septum. Firstly 12.2 ml (50 mmol) of BSA and, after stirring for 30 min, a further 7 ml (28 mmol) of BSA were then added by means of syringe. After heating to 40° C. for a short time, the reaction mixture clarified. 13 ml (72 mmol) of TMSOTf were added by means of syringe at room temp. After one hour, no product formation was yet observed (TLC checking, AcOEt/n-heptane 1:1). A further 13 ml (72 mmol) of TMSOTf were therefore added. Subsequently, the reaction mixture was heated to 50° C. After stirring at 50° C. for 2.5 h (TLC checking), the mixture was cooled to RT., [lacuna] onto an ice-cold mixture of 250 ml of AcOEt and 190 ml of satd. NaHCO3 solution and intensively extracted by stirring for 10 min. It was again washed with 100 ml of NaHCO3 solution and the aqueous phases were again extracted with 100 ml of AcOEt. The dil. org. phases were dried using MgSO4 and the solvents were removed in vacuo in a rotary evaporator. After drying in an oil pump vacuum, 20.9 g of crude product were obtained. Chromatography on silica gel (h=25 cm, f=5 cm, AcOEt/n-heptane 1:1) yielded a TLC-uniform, foamy product, which was digested using Et2O. Filtration and drying in an oil pump vacuum afforded 15 g (86%) of 34.

Provenance & Evidence