Synthesis of 3-acetamido-3-deoxy-(1 -> 5)-alpha-D-ribofuranan by ring-opening polymerization of 1,4-anhydro-3-azido-alpha-D-ribopyranose derivative

A stereoregular 3-acetamido-3-deoxy-(1-->5)-alpha-D-ribofuranan (3AAdRF) wa s synthesized by the synthetic route starting from selective ring-opening p olymerization of I,4-anhydro-3-azido-2-O-t-butyldimethylsilyl-3-deoxy-alpha -D- ribopyranose (A3ASR). A3ASR was polymerized by BF3. OEt2 catalyst at lo w temperature to give 3-azido-2-O-t-butyldimethylsilyl-(1 -->5)-alpha-D-rib ofuranan (3AzSRF) with M-n of 1.4 x 10(4)-1.9 x 10(4) and [alpha](D) of +24 9- +266 degrees. 3AzSRF was reduced with NaBH4 in a tetrahydrofuran (THF)-e thanol mixture to afford 3-amino-2-O-t-butyldimethylsilyl-3-deoxy(1-->5)- a lpha-D-ribofuranan (3AmSRF). Acetylation of the amino group in 3AmSRF produ ced 3-acetamido-ribofuranan derivative (3AAdSRF), and then desilylation of the 3AAdSRF gave 3AAdRF with iii, ranging from 9.4 x 10(3) to 10.5 x 10(3) and [alpha](D) of +195 degrees. The structure analysis was performed by C-1 3 and H-1 NMR spectroscopy, IR spectroscopy, and optical rotation measureme nts.