Convenient synthesis of 2,3-O-isopropylidene-5-thio-d-ribose and 5-thio-d-ribose; synthesis of 1,4-anhydro-2,3-O-isopropylidene-α-d-ribopyranose and 1,4-anhydro-2,3-O-isopropylidene-5-thio-α-d-ribopyranose

Sequential mesylation–acetylation of 2,3-O-isopropylidene-d-ribofuranose gave 1-O-acetyl-2,3-O-isopropylidene-5-O-methanesulfonyl-β-d-ribofuranose that was converted into 1-O-acetyl-5-(S)-acetyl-2,3-O-isopropylidene-5-thio-β-d-ribose, deacetylation of which gave 2,3-O-isopropylidene-5-thio-d-ribose as the β-pyranose form, which was hydrolysed to 5-thio-d-ribose. 1,4-Anhydro-2,3-O-isopropylidene-α-d-ribopyranose was obtained by sodium methoxide treatment of 1-O-acetyl-2,3-O-isopropylidene-5-O-methanesulfonyl-β-d-ribofuranose and 1,4-anhydro-2,3-O-isopropylidene-5-thio-α-d-ribopyranose was similarly synthesised via 1-(S)-acetyl-2,3-O-isopropylidene-5-O-methanesulfonyl-5-thio-α-d-ribofuranose.