A synthesis of [2.2.1]bicyclo nucleosides which is shorter and provides higher overall yields proceeds via the key intermediate of the general formula III, wherein R
4
and R
5
are, for instance, sulfonates and R
7
is, for instance, a halogen or an acetate. From compounds of the general formula II, such as 3-O-aryl-4-C-hydroxymethyl-1,2-O-isopropylidene-&agr;-D-ribofuranose, intermediates of the general formula III are suitable for coupling with silylated nucleobases. Upon one-pot base-induced ring-closure and desulfonation of the formed [2.2.1]bicyclo nucleoside, a short route to each the LNA (Locked Nucleic Acid) derivatives of adenosine, cytosine, uridine, thymidine and guanidine is demonstrated. The use of the 5′-sulfonated ring-closed intermediate also allows for synthesis of 5′-amino- and thio-LNAs.
1
通过通式III的关键中间体进行合成[2.2.1]双环核苷,该方法较短且提供更高的总收率,其中R4和R5例如为
磺酸盐,R7例如为卤素或
醋酸盐。从通式II的化合物,例如3-O-芳基-4-C-羟甲基-1,2-O-异丙基亚-
D-核糖,通式III的中间体适用于与
硅化核苷碱进行偶联。通过一锅法碱催化环闭合和去
磺酸化形成的[2.2.1]双环核苷,演示了
腺嘌呤、
胞嘧啶、尿
嘧啶、胸腺
嘧啶和
鸟嘌呤的LNA(锁定核酸)衍
生物的短路线。使用5'-
磺酸化环闭合中间体还允许合成5'-
氨基和
硫代-LNA。