Simple Synthesis of 3,5-Di-O-Substituted 1,4-Anhydro-2-deoxy-D-Erythro-pent-1-enitol from D-Ribose

1,4-zAnhydro-2-deoxypent and hex-1-enitols (furanoid glycals) are readily available by a number of reductive methods from corresponding furanoid glycosyl halides.1–5 The crucial problem of their synthesis is related to the accessibility of the appropriate protected sugar having a free anomeric hydroxyl which allows introduction of the halide. Readily available 2,3:5,6-di-O-isopropylidene-d-mannose (1) and 2,3-O-isopropylidene-5-O-methoxymethyl-d-ribose (2), which is not so available, are the most common substrates used to provide alternative cis and trans disubstituted dihydrofurans 3 and 4, respectively (SCHEME 1).1–5