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.
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0358, USA.
Brandon I
BI
Morinaka
Joseph R
JR
Pawlik
Tadeusz F
TF
Molinski
D000818:Animals; D002942:Circular Dichroism; D007093:Imidazoles / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D011161:Porifera / Q000737:chemistry* / Q000378:metabolism*; D013256:Steroids / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*
D007093:Imidazoles; D013256:Steroids