Mycalamides C and D, Cytotoxic Compounds from the Marine Sponge Stylinos n. Species Jamie S. Simpson, † Mary J. Garson, † John W. Blunt, ‡ Murray H. G. Munro,* ,‡ and John N. A. Hooper § Department of Chemistry, The University of Queensland, Brisbane, Queensland 4072, Australia, Department of Chemistry, The University of Canterbury, Christchurch, New Zealand, and Queensland Museum, P.O. Box 3300, South Brisbane, Queensland 4101, Australia Received September 3, 1999 The new cytotoxic compounds, mycalamides C (3) and D (4), have been isolated from the marine sponge Stylinos n. sp., along with the known theopederin E (1) and mycalamide A (2). Since the isolation of mycalamide A, a potent antiviral and cytotoxic compound from a sponge of the genus Mycale, a number of related metabolites have been isolated. 1 Mycalamide B was described a short time later from the same New Zealand sponge. 2 The isolation of the water- soluble onnamide A from a Japanese specimen of a The- onella sp. occurred at the same time as the isolation of mycalamide A 3 and was followed by the isolation of several other examples of onnamides, also from the genus Theon- ella. 4,5 More recently Fusetani et al. reported the isolation of a related series, named the theopederins, from a Japanese specimen of the genus Theonella. 6 These com- pounds all share common features with the terrestrial natural product pederin, the principal component of the blister beetle. 7 Extracts of a soft-textured, yellow-orange sponge from Heron Island, later identified as Stylinos n. sp. (family Mycalidae, order Poecilosclerida, class Demospongiae), were highly active in P-388 assays (IC 50 ) 16.5 ng/mL). Fractionation of a small quantity of extract on Si gel, followed by bioassay of the resulting fractions, indicated the active components were polar. Extraction of a larger recollection of the sponge (1.12 kg) resulted in a (DCM) extract that had potent bioactivity [P-388; (IC 50 ) 22 ng/ mL)]. Reversed-phase flash chromatography 8 resulted in a series of fractions that were combined on the basis of TLC, NMR, and bioassay results. The major bioactive fraction was partitioned further on a DIOL flash column, giving the known theopederin E (1) and mycalamide A (2), both having spectral data identical with those reported in the literature. 1,2,6 Reversed-phase HPLC of a more polar fraction eluting with 30% acetonitrile-water resulted in the isolation of mycalamide C (3) and mycalamide D (4). The 1 H NMR spectrum of mycalamide C (3) was similar to that of theopederin E (1), although it had one less methoxy signal and no dioxolane methylene signals. LR- FABMS mass spectral measurement of 3 gave a molecular ion at 418 mass units [MH + ] for which high-resolution analysis gave the molecular formula C 20 H 36 NO 8 , in agree- ment with the missing NMR signals. Analysis of the DQF- COSY spectrum showed correlations from the NH signal at δ 7.07 to the methylene signal at δ 3.70 (H10), and then to δ 4.15, showing that C10 was not oxygenated. Detailed analysis of the DQF-COSY and HMBC spectra showed the remainder of the carbon skeleton was identical to that of theopederin E. The methoxy signal at δ 3.29 showed an HMBC correlation to C6, establishing its position. The 1 H NMR spectrum of mycalamide D (4) showed marked similarities to that of mycalamide A (2), but also contained one less methoxy signal. LRFABMS measure- ment gave a molecular ion at 512 mass units [MNa + ], 14 mass units less than mycalamide A (2). High-resolution analysis corresponded to the molecular formula C 23 H 39 - NO 10 Na. Analysis of DQF-COSY and HMBC spectra showed that the carbon skeleton was identical to that of mycalamide A (2). The methoxy signal at δ 3.29 showed an HMBC correlation to C6, establishing its position and confirming that the methyl group was missing from the C13 oxygen. 1 H and 13 C NMR data for 1-4 are compared in Tables 1 and 2. The optical rotations measured for theopederin E (1) (+110°) and mycalamide A (2)(+84°) agreed with literature * To whom correspondence should be addressed. Tel.: (+64) 3-364-2434. Fax: (+64) 3-364-2110. E-mail: m.munro@chem.canterbury.ac.nz. † University of Queensland. ‡ University of Canterbury. § Queensland Museum. 704 J. Nat. Prod. 2000, 63, 704-706 10.1021/np990431z CCC: $19.00 © 2000 American Chemical Society and American Society of Pharmacognosy Published on Web 04/20/2000