Pentamethyl-_m_-digallic acid methyl ester, C_20H_22O_9.
Pentacetyl-_m_-digallic acid, C_24H_20O_14.
Pentamethyl-_m_-digallic acid, C_19H_20O_9.
Pentamethyl-_m_-digalloyl chloride, C_19H_19O_8Cl.
Pentamethyl-_p_-digallic acid, C_19H_20O_9.
Pentamethyl-_p_-digallic acid methyl ester, C_20H_22O_9.

Hydrolysis of digallic acid yields gallic acid; oxidation, on the other
hand, ellagic acid and luteic acid (Luteo Saure), which can be separated
by shaking with pyridine. The reduction of digallic acid yields, by
different methods, the same reduction compound, [Footnote: Nierenstein,
Abderhalden's "Handb. d. biochem. Arbeitsm.," vi. 154.] viz., the
racemic leucodigallic acid, which differs from digallic acid by being
devoid of any tannoid properties; the latter distinction may be ascribed
to the transformation of the tannophor group--CO.O--, to the
tannoid-inactive group CH(OH)--O--.

The successful resolving of racemic leucodigallic acid into both of its
optically active components can only be brought about through the _d_-
or _l_-hexacarbethoxyleucodigallic acid on introducing the latter into a
1 per cent. pyridine solution and heating to 45 -50 C., whereby the
_d_- or _l_-acid is formed accompanied by a strong evolution of carbon
dioxide.

Hydrolysis of leucogallic acid yields gallic acid and gallic aldehyde;
oxidation by means of hydrogen peroxide yields ellagic acid and luteic
acid, and oxidation with potassium persulphate and sulphuric acid, in
acetic acid solution, yields purpurotannin (see below) [Footnote:
Liebig's _Ann_., 1912, 386, 318.].