812 Wisconsin Academy of Sciences, Arts, and Letters. 
II. A. 1. a.) Trihydroxy derivatives of diphenyl methanone. 
Cotoin,—Dihydroxy-1, 5-methoxy-3-diphenyl methanone. 
CH COH 
Cotoin is a trihydroxy derivative of diphenyl ketone, referable 
to a penthydroxide of the underlying hydrocarbon. It occurs 
in the bark of coto 1 and para coto, obtained from Brazil. 
Cotoin 2 forms colorless or only slightly yellow crystals 
which melt at 130°. With caustic alkalies it forms a yellow 
solution. In 1894 Ciamician and Silber 3 partially determined 
the constitution of cotoin. Pollock, 4 in 1901, completed this 
by determining the position of the hydroxy groups. 
In the bark of para coto cotoin is accompanied by a series of 
closely related compounds, hydrocotoin, methyl hydrocotoin, 
protocotoin and methyl protocotoin. These compounds, all of 
which closely resemble cotoin, were first studied by Jobst and 
Hesse 5 in 1879. In 1891-1892 Ciamician and Silber 6 made a 
further investigation of this series of pigments and determined 
their relation to cotoin and to each other. This relationship is 
best illustrated by the following series of partly analyzed for¬ 
mulae : 
C fi H s 
■o ch 3 
rO CH 3 r 
OH 
o CH, 
' OH 
c 6 H 2 - 
3 p TT 
0 H • 
coc 6 h 5 
coc 6 h 5 
Cotoin. 
Hydrocotoin 
0 CH 3 
0 CH 3 
0 CH 3 
COC 6 H 5 
Methyl hydrocotoin 
1 Neues. Kept. f. Pharrn., 25, p. 23. 
2 Ann., 199, p. 17. 
3 Ber., 27, p. 1497. 
4 Monats., 18, p. 738; 22, p. 996. 
6 Ann., 199, p. 17. 
6 Ber., 24, p. 299, 2977; 25, p. 1119. 
