Preparation, structural elucidation and reactions of benzyl 2-deoxy-3,5-di-O-methyl-1,4-dithio-l-threo-pentofuranoside and synthesis of the corresponding 2′-deoxy-4′-thionucleosides

Benzyl 2-deoxy-3,5-di-O-methyl-1,4-dithio-l-threo-pentofuranoside (5) is synthesized in five steps starting with 2-deoxy-d-ribose. The anomers 5α and 5β are separated and their configuration is unequivocally assigned by use of NOE measurements. 2-Deoxy-3,5-di-O-methyl-4-thio-l-threo-pentofuranose is obtained from 5 and mercuric 4-nitrobenzoate. The corresponding nucleosides are prepared from 5 and bis-(trimethylsilyl)uracil or bis-(trimethylsilyl)thymine in the presence of N-iodosuccinimide.