Fuscinic acid dimethyl ether

The cyclopentapyrazoles (45 R = H, Me) are obtained in 67% and 54% yields, respectively, by benzilic acid rearrangement of the corresponding indazolediones (44). This ring contraction has many analogs in the next section, and may occur during alkaline permanganate oxidations of suitable substrates. For example, oxidation of fuscinic acid dimethyl ether (46) affords (48) and (49), implicating the a-diketone (47) as a common intermediate. ... 

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