By reaction of theophylline-7-acetaldehyde (I) with ethylene glycol (II) by means of p-toluenesulfonic acid in refluxing benzene.
Condensation of 1-(b-L-ribofuranosyl)thymine (XXXVI) with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane (XXXVII) in pyridine gives the cyclic disiloxane nucleoside (XXXVIII), which is acylated with thiocarbonyldiimidazole (TCDI) in DMF to yield the 2'-O-thioester derivative (XXXIX). Reduction of this compound by means of 2,2'-azobis(methylpropionitrile) (ABMP) and Bu3SnH in refluxing toluene affords the silylated 2'-deoxynucleoside (XL), which is finally desilylated by means of TBAF in THF.