De Novo Synthesis of Benzosceptrin C and Nagelamide H from 7-15N-Oroidin: Implications for Pyrrole–Aminoimidazole Alkaloid Biosynthesis

E. Paige Stout†, Brandon I. Morinaka†, Yong-Gang Wang§, Daniel Romo§, and Tadeusz F. Molinski*†
†Department of Chemistry and Biochemistry and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0358, United States
§ Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, United States
J. Nat. Prod., Article ASAP
DOI: 10.1021/np300051k
Publication Date (Web): March 28, 2012

De novo synthesis of the natural products benzosceptrin C (7) and nagelamide H (8) was achieved using cell-free enzyme preparations from the marine sponges Agelas sceptrum and Stylissa caribica employing synthetic 7-¹⁵N-oroidin. These studies provide direct experimental evidence to support the long-standing, but untested, hypothesis that oroidin is a precursor to more complex pyrrole–aminoimidazole alkaloids, such as the sceptrins, benzosceptrins, and nagelamides. In addition, a new nagelamide, didebromonagelamide A (5b), was isolated from S. caribica, representing the first report of a nagelamide-like compound from the Caribbean.

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