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Dipyrrinone analogs of xanthobilirubic acid, 5‐[1,5‐didehydro‐3‐ethyl‐4‐methyl‐5‐oxo‐2H‐pyrrol‐2‐ylidene)‐methyl]‐2,4‐dimethyl‐1H‐pyrrol‐3‐propanoic acid, with alkanoic acid chain lengths varying from formic to caproic have been synthesized as their methyl esters and characterized spectroscopically. All of the dipyrrinones studied exhibit intermolecular hydrogen bonding in chloroform, as detected by 1H‐nmr, and the influence of the carboxyl group on the uv‐visible spectrum decreases with increasing chain length.

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