【摘 要】
：
5-Esters of nucleosides with amino acids bear better oral bioavailability due to active transportation via the intestinal oligopeptide transporter 1 (PepT 1).[1,2] Here was reported a regionselective
【机 构】
：
School of Pharmaceutical Engineering,and Key Laboratory of Structure-Based Drug,Design & Discovery (
【出 处】
：
The 24th International Society of Heterocyclic Chemistry Con
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5-Esters of nucleosides with amino acids bear better oral bioavailability due to active transportation via the intestinal oligopeptide transporter 1 (PepT 1).[1,2] Here was reported a regionselective synthesis of the 5-esters of Cytarabine (R=OH, R"=H) or Gemcitabine (R=R"=F) (2).Thus, the nucleosides was first selectively protected with TrC1 at 5-position, and then treated with allyloxycarbonyl chloride (AOC-C1) to protect all other active functionalities.After removal of Tr group, the obtained compound 3 was condensed with Boc-protected amino acids at 5-position, the AOC was successfully cleaved by using Pd-catalyzed method.Finally, the Boc group was removed under acidic condition to afford the 5-esters in hydrochloric salt forms (1).The overall yield reached up to 40％ in 6 steps without column separation.
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