We are deeply grateful to Professor William Fenical (Scripps Institution of Oceanography) for his invaluable advice and support, and for generously providing samples of the crude extracts of Aspergillus sp. (CNC358). We are indebted to Professor Axel Zeeck, Dr. Jennifer Qian-Cutrone of BMS, and Pfizer for authentic samples of avrainvillamide, stephacidin B, and CJ-17,665, respectively. Ms. Sarah Siegel of the Kelly group is acknowledged for expertise in obtaining CD spectra. We thank Dr. D.-H. Huang and Dr. L. Pasternak for assistance with NMR spectroscopic studies, and Dr. G. Suizdak for assistance with mass spectrometry measurements. We thank Biotage for a generous donation of process vials that were used extensively during these studies. Financial support for this work was provided by The Scripps Research Institute, Eli Lilly & Co, GlaxoSmithKline, the Searle Scholarship fund, and the NIH (predoctoral fellowship to C.A.G.). CJ-17,665 is the name given to avrainvillamide isolated independently from a soil sample collected in Venezuela.