Of the crystalline constituents of the mycelium of Oospora sulphurea-ochracea described in the previous communication, ⁽¹⁾ sulochrin (substance B) was proved by further experiments to be methyl ester of 2: 6: 4'-trihydroxy-4-methyl-6'-methoxybenzophenone-2'-carboxylic acid, the structural discussion having been advanced in detail in a separate paper.⁽²⁾
Of the three hydroxyl groups which are present in the sulochrin molecule two could be readily methylated by means of diazomethane ; one of the two hydroxyl groups in the p-orsellinic moiety situated at ortho-position to the central carbonyl resisted this means of methylation.
The fully methylated derivative has now been prepared by repeated application of dimethylsulphate on sulochrin. Trimethylsulochrin thus obtained can be split neatly into two halves by means of conc. sulphuric acid followed by the addition of water, just as in the case of sulochrin and dimethylsulochrin, resulting fragments being, as is anticipated, dimethyl-p-orsellinic acid and methyl dimethyl-α-resorcylate and thus giving an additional evidence of the structure of sulochrin. A more drastic measure of hydrolysis, however, is required in this case. While in the case of solochrin and dimethylsulochrin extreme decomposition had to be controlled by ice-cooling the mixture, for the complete hydrolysis of trimethylsulochrin it was necessary to warm the sulphuric acid solution for some time on a water-bath.
Action of methyl alcoholic potash on trimethylsulochrin yields monomethyltetramethoxy-benzophenonecarboxylic acid which is isomeric with dimethylsulochrin, one methoxyl of ester-form having been lost.

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