Nucleoside und Nucleotide. Teil 10. Synthese von Thymidylyl‐(3′‐5′) ‐thymidylyl‐(3′‐5′)‐1‐(2′‐desoxy‐β‐ D ‐ribofuranosyl)‐2(1 H )‐pyridon

Nucleosides and Nucleotides. Part 10. Synthesis of Thymidylyl‐(3′‐5′)‐thymidylyl‐(3′‐5′)‐1‐(2′‐deoxy‐β‐ D ‐ ribofuranosyl)‐2(1 H )‐pyridone The synthesis of 5′‐ O ‐monomethoxytritylthymidylyl‐(3′‐5′)‐thymidylyl‐(3′‐5′)‐1‐(2′‐deoxy‐β‐ D ‐ribofuranosyl)‐2(1 H )‐pyridone ((MeOTr)T d pT d p∏ d , 5 ) and of thymidylyl‐(3′‐5′)‐thymidylyl‐(3′‐5′)‐1‐(2′‐deoxy‐β‐ D ‐ribofuranosyl)‐2(1 H )‐pyridone (T d pT d p∏ d , 11 ) by condensing (MeOTr) T d pT d ( 3 ) and p∏ d (Ac) ( 4 ) in the presence of DCC in abs. pyridine is described. Condensation of (MeOTr) T d pT d p ( 6 ) with Π d (Ac) ( 7 ) did not yield the desired product 5 because compound 6 formed the 3′‐pyrophosphate. The removal of the acetyl‐ and p ‐methoxytrityl protecting group was effected by treatment with conc. ammonia solution at room temperature, and acetic acid/pyridine 7 : 3 at 100°, respectively. Enzymatic degradation of the trinucleoside diphosphate 11 with phosphodiesterase I and II yielded T d , pT d and p∏ d , T d p and Π d , respectively, in correct ratios.