Amaranzoles B-F, imidazole-2-carboxy steroids from the marine sponge Phorbas amaranthus. C24-N- and C24-O-analogues from a divergent oxidative biosynthesis.

Five new steroidal imidazoles, amaranzoles B-F, were isolated from extracts of the marine sponge Phorbas amaranthus along with the known amaranzole A. The C24-N-(4-p-hydroxyphenyl)imidazol-5-yl constitution found in amaranzoles A, C, and D is replaced by a C24-O-(4-p-hydroxyphenyl)imidazole-2-carboxylate motif in amaranzoles B, E, and F. The structures were elucidated by interpretation of spectroscopic data. The C24 side chain configuration was assigned by synthesis of a model ester followed by chiroptical comparisons of its CD spectrum with that of an amaranzole B derivative.

Citation

Brandon I Morinaka, Joseph R Pawlik, Tadeusz F Molinski. Amaranzoles B-F, imidazole-2-carboxy steroids from the marine sponge Phorbas amaranthus. C24-N- and C24-O-analogues from a divergent oxidative biosynthesis. The Journal of organic chemistry. 2010 Apr 16;75(8):2453-60

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PMID: 20235564

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