quinoline with an excess of tricarbomethoxygalloyl chloride for
twenty-four hours and precipitating the resulting product with methyl
alcohol; suitably purified, a light amorphous colourless substance was
obtained which proved to be penta-(tricarbomethoxygalloyl)
glucose. Careful saponification with excess alkali in acetone-aqueous
solution at room temperature yielded a tannin very closely resembling
tannin, identified as pentagalloyl glucose. It is doubtful, however,
whether this substance is homogeneous, and it is probably a mixture of
two stereoisomers.

Fischer and Freudenberg, therefore, further concluded that tannin is
mainly an ester compound of glucose and 5 molecules _m_-digallic
acid. Elucidation on this point offered itself advantageously in
Herzwig's methylotannin, [Footnote: _Ber._, 1905, 38, 989.] which is
obtained by the interaction of diazomethane and tannin. The first step
was then to prepare pentamethyl-_m_-digallic acid

CH_3.O_______ ______COOH
CH_3.O{_______}--CO.O--{______}
CH_3.O CH_3.O O.CH_3

from trimethylgalloyl chloride and the _m-p_-dimethyl ether of gallic
acid; the chloride of this substance, coupled with [Greek: a]- and
[Greek: b]-glucose, yields--

_CH.OR
| |
| CH.OR H_______O.CH_3
| | R=CO{_______}O.CH_3
O{ CH.OR H O