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Two pyrrololactams, likely degradation products of more complex known guanidines, were isolated from several marine sponges. 5-Bromo- and 4,5-dibromopyrrole-1-carboxylic acid methyl esters were also isolated. A complex guanidine metabolite, poorly soluble in DMSO, was found to give sharp, reproducible nmr spectra in acid media.
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Schmitz et al. (1985) studied this question.
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