Application of the concept of transient protection to the synthesis of protected deoxynucleosides is described. The deoxynucleosides are first treated with trimethylchlorosilane in pyridine for protection of the hydroxyl groups, and then immediately reacted with an acylating agent-benzoyl chloride for la and lb and isobutyric anhydride for ic-to effect N-acylation. Hydrolysis of the trimethylsilyl groups takes a few hours in aqueous pyridine or a few minutes with dilute ammonia. The ammonia also effects selective hydrolysis of the initially formed TV,TV-dibenzoyldeoxyadenosine derivative (3a) to the desired TV-benzoyldeoxyadenosine (4a). This one-flask procedure gives crystalline TV-acyl deoxynucleosides 4a and 4b in 95% yield and 4c in 75% yield, in only a few hours. The 5'-0-dimethoxytrityl deoxynucleosides 8a and 8b are also obtained in a one-flask procedure by initial reaction of the deoxynucleosides with 4,4/-dimethoxytrityl chloride, followed by treatment with trimethylchlorosilane and then benzoyl chloride. Although with deoxycytidine some of the 4-TV,5,-0-bis(dimethoxytrityl) derivative (5c) is formed, benzoyl chloride effects conversion to the 4-TV-benzoyl derivative (7b). After simple purification by flash chromatography 8a and 8b are each obtained in 80-90% overall yield from la or lb.(1) This work has been reported briefly, see "Abstracts of Papers", 181st

Die Anwendung eines Konzeptes zum vorübergehenden Schutz von Desoxynucleosiden wird beschrieben.