The title compound was prepared via hetero-Diels–Alder reaction of 1-acetoxy-1, 3- butadiene and thioaldehyde, followed by Pummerer rearrangement. Different from the corresponding sugar and 5a-carba sugar, C-inside isomer of 1, 5-anhydro-4, 6-O- benzylidene-2, 3-dideoxy-5-thio-dl-thero-hex-2-enitol was found to be thermodynamically more stable than the corresponding O-inside one and these thermodynamic stabilities ...