Hydroxylation, of glycals

It has been recognized since 1931 that hydroxylation of glycals with peroxybenzoic acid results mainly in m-2,3-diols, whereas the compounds having trans groups at C-2 and C-3 preponderate amongst the oxidation products of glycals substituted at C-3. These findings are closely paralleled by the results of peroxidation of the model compounds cyclohex-2-en-l-ol (35, R = H) and its acetate (35, R = Ac) whereas... 

Similarly to many other great discoveries, the molybdic acid catalyzed interconversion of epimeric aldoses is the result of serendipity. Thus, when D-talose, obtained from another, lesser-known reaction also discovered by V. Bflik, namely the stereoselective, molybdate-catalyzed hydroxylation of glycals [3], was repeatedly recrystalHzed (in the presence of a catalyst that had not been completely removed), it was not possible to obtain it in a pure condition, as the aldose slowly epimerized to D-galactose [4]. A simple verification of the explanation of this originally imdesirable interconversion, the treatment of D-galac-... 

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