Hamameli-tannin structure

The carbon-chain structure of the sugar obtained from hamameli-tannin was established by the classical method of Kiliani,26 which is based on the reduction, with hydrogen iodide, of polyhydroxy acids to fatty acids. Treatment of the calcium salt of hamamelonic acid under these conditions led to inconclusive results. The reduction of the corresponding, crystalline ammonium salt, however, furnished 3.5 to 5% of 2-methylvaleric acid, which was identified by the properties of its crystalline p-iodophenacyl ester. Thus, it was proved that the sugar must have structure XIV. 

The bark of the North American shrub Hamamelis virginica contains in addition to other tannins, about 1 to 2% of crystalline hamameli-tannin (XVI) 97). The substance has the composition of a di-O-galloylhexose, and on acid or enzyme hydrolysis, it gives two moles of gallic acid and one mole of an unusual hexose, hamamelose (XVII), whose structure has been established as 2-C-(hydroxymethyl)-D-ribose (XVII) 101). 

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