Synthesis of New 2‘,3‘-Dideoxy-6‘,6‘-difluoro-3‘-thionucleoside from <i>g</i><i>em</i>-Difluorohomoallyl Alcohol

2‘,3‘-Dideoxy-6‘,6‘-difluoro-3‘-thionucleoside 1b, an analogue of 3Tc that has high biological activities against HIV and HBV, has been synthesized from gem-difluorohomoallyl alcohol 3 in an efficient way. The key intermediate 4-amino-3,3-difluorotetrahydrothiophen-2-ylmethyl benzoate 15 was prepared from 2,2-difluoro-1-[(4R)-2,2-dimethyl-1,3-dioxolan-4-yl]but-3-en-1-ol 3 in 11 steps. The construction of pyrimidine ring with the amino group of compound 15 gave the target compound 1.