product was analyzed by high performance chromatography hplc with a reverse phase octadecyl silica gel column using a mixture of acetonitrile water 75 25 as an eluent and using a uv detector 254 nm indicating a purity of 99 5 a major impurity was 3 u2032 5 u2032 o bis 4 4 u2032 dimethoxytrityl thymidine with an hplc peak area of 0 3 an yield was 67 nmr u03b4 cdcl 3 8 7 s 1h 7 6 s 1h 7 2 7 4 m 9h 6 8 m 4h 6 4 t 1h 4 6 m 1h 4 1 m 1h 3 8 s 6h 3 4 m 2h 2 3 2 5 m 3h including ch 2 in mibk 2 1 m 1 5h coch 3 in mibk 1 7 m 0 5h ch in mibk 1 5 s 3h 0 9 d 3h ch 3 u00d7 2 in mibk mibk an abbreviation for 4 methyl 2 pentanone ir cm u2212 1 kbr 3163 1698 1608 1509 1259 1177 1098 1033 830 to a stirred solution of 40 0 g of thymidine 0 165 mol in 500 ml of pyridine was added 56 0 g of dimethoxytrityl chloride 0 165 mol and the mixture was stirred at room temperature for 3 hours to the mixture 16 7 g of sodium hydrogen carbonate was added the resulting mixture was stirred at room temperature for 30 min and evaporated under a reduced pressure to the residue was added 500 ml of n butyl acetate to the stirred mixture was added 500 ml of water and the mixture was stirred for 10 min then the organic layer.