Note pubs.acs.org/jnp
Biologically Active Acetylenic Amino Alcohol and N‑Hydroxylated 1,2,3,4-Tetrahydro-β-carboline Constituents of the New Zealand Ascidian Pseudodistoma opacum Jiayi Wang,† A. Norrie Pearce,† Susanna T. S. Chan,†,‡ Richard B. Taylor,§ Michael J. Page,⊥ Alexis Valentin,∥ Marie-Lise Bourguet-Kondracki,∇ James P. Dalton,□, # Siouxsie Wiles,□, # and Brent R. Copp*,†, # †
School of Chemical Sciences, □Bioluminescent Superbugs Lab, Department of Molecular Medicine and Pathology, and #Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand § Leigh Marine Laboratory, Institute of Marine Science, University of Auckland, PO Box 349, Warkworth 0941, New Zealand ⊥ National Institute of Water & Atmospheric Research (NIWA) Ltd, PO Box 893, Nelson 7010, New Zealand ∥ Université Paul Sabatier, PHARMA-DEV, UMR 152 IRD-UPS, Université de Toulouse, 118 Route de Narbonne, F-31062 Toulouse Cedex 9, France ∇ Laboratoire Molécules de Communication et Adaptation des Micro-organismes, UMR 7245 CNRS, Muséum National d’Histoire Naturelle, 57 Rue Cuvier (C.P. 54), 75005 Paris, France S Supporting Information *
ABSTRACT: The first occurrence of an acetylenic 1-amino-2-alcohol, distaminolyne A (1), isolated from the New Zealand ascidian Pseudodistoma opacum, is reported. The isolation and structure elucidation of 1 and assignment of absolute configuration using the exciton coupled circular dichroism technique are described. In addition, a new N-9 hydroxy analogue (2) of the known P. opacum metabolite 7-bromohomotrypargine is also reported. Antimicrobial screening identified modest activity of 1 toward Escherichia coli, Staphylococcus aureus, and Mycobacterim tuberculosis, while 2 exhibited a moderate antimalarial activity (IC50 3.82 μM) toward a chloroquine-resistant strain (FcB1) of Plasmodium falciparum.
A
reported to contain an alkyne functionality. Our previous studies on Pseudodistoma species ascidians collected from New Zealand waters have led to the characterization of purines and tetracyclic 6-hydroxyquinoline alkaloids from P. aureum9 and, more recently, 1,2,3,4-tetrahydro- and fully oxidized β-carbolines from P. opacum.10 As a continuation of our studies of the chemistry of New Zealand ascidians, we now describe a diynecontaining 1-amino-2-alcohol lipid, distaminolyne A (1), and a moderately antimalarial N-hydroxy analogue of 7-bromohomotrypargine, 2, from P. opacum specimens collected at a different site from our previous material. Assignment of the absolute configuration of 1 was made using the exciton coupled circular dichroism (ECCD) technique, and antibacterial activities are reported. Specimens of the ascidian were collected from shallow water at Ti Pt., Northland, New Zealand, and identified by one of us (M.J.P.) as Pseudodistoma opacum. A MeOH extract of a freezedried sample was initially fractionated by C18 reversed-phase flash column chromatography. The 75% MeOH/H2O (TFA)
large number of bioactive acetylenic lipids have been isolated from natural sources, spanning micro-organisms, fungi, higher plants, and marine organisms.1 The dominant marine sources, sponges and algae, have yielded acetylenic alcohols or carboxylic acids, many of which exhibit biological activities including cytotoxicity and antimicrobial properties.2 Biogenesis of plant/bacterial3-derived acetylenic lipids proceeds via the action of desaturases (alkene formation) or acetylenases (alkyne formation) on full-length fatty acids.4 To date only one publication describes the isolation of acetylenic lipids from marine organisms of the class Ascidiacea (ascidians), with four C21 linear acetylenic alcohols being reported from an unidentifiable specimen.5 Our ongoing reversed-phase HPLC-DAD screening of extracts of New Zealand ascidians has repeatedly identified the presence of relatively long retention time, lipid metabolites that exhibit UV spectra [λmax 240, 253, 267, and 283 nm] diagnostic of the presence of acetylenic groups.6 The ascidians in question are typically of the genus Pseudodistoma, a group of organisms well recognized for their propensity to biosynthesize 2-amino, 1-amino-2-alcohol, and 2-amino-3-alcohol lipids.7 In many examples, the lipid chain, which is presumed to be derived from fatty acid biosynthesis,8 contains varying degrees of unsaturation in the form of E- and/or Z-alkenes. Prior to this current work, no examples of lipid amino alcohols have been © XXXX American Chemical Society and American Society of Pharmacognosy
Special Issue: Special Issue in Honor of John Blunt and Murray Munro Received: August 27, 2015
A
DOI: 10.1021/acs.jnatprod.5b00770 J. Nat. Prod. XXXX, XXX, XXX−XXX
Journal of Natural Products
Note
resonances, at δC 78.0, 77.1, 66.7, and 66.3, suggestive of the presence of two alkyne groups, the conjugated nature of which was confirmed by the observation of characteristic UV absorbances at 226, 240, 253, 267, and 283 nm.6 With all degrees of unsaturation accounted for, the remaining issue was the location of the diyne moiety in 1. Analysis of HSQCTOCSY data established partial structures of an alkyl 1-amino2-alcohol (C-1 to C-5/6) and CH2CH−CH2−CH2− (C-14 to C-17). HMBC correlations observed between olefinic methine H-16 (δH 5.85) and 13C resonances at δC 33.7 (C15) and 19.6 (C-14) supported the presence of this latter substructure, while correlations observed from δH 2.33 (H2-14) to resonances at δC 77.1 (C-13) and 66.7 (C-12) identified connectivity to the diyne fragment. HMBC correlations linking the diyne to the remaining alkyl 1-amino-2-alcohol structural fragment [δH 1.50 (H2-8) to δC 78.0 (C-10); δH 2.25 (H2-9) to δC 78.0 and 66.3 (C-11)] then helped secure the structure as 1aminoheptadeca-16-en-10,12-diyn-2-ol, which we have named distaminolyne A (1). Assignment of absolute configuration was achieved using the dibenzoate exciton coupled circular dichroism method.11 Reaction of 1 with benzoyl chloride in pyridine with N,N-dimethylaminopyridine (DMAP) gave, after repeated chromatography, N-benzoyl 3 and N,O-dibenzoyl derivative 4 in low yields. The ECD spectrum of 4 (Figure S11) exhibited a bisignate curve with a positive first Cotton effect (Δε −6.6, 222 nm; 0, 231; +6.1, 239), which according to literature precedent corresponds to the 2S configuration.11,12 The H2O (TFA) and 10% MeOH/H2O (TFA) fractions were judged by NMR to contain predominantly a single 1,2,3,4tetrahydro-β-carboline alkaloid, which was purified by repeated C2 flash column chromatography to give 2 as an optically inactive yellow oil. Mass spectrometric analysis of 2 ((+)-HRESIMS m/z 380.1059 and 382.1050 [M + H]+) determined a free base molecular formula for the alkaloid of C15H22BrN5O, being 16 mass units (one oxygen atom) more than that observed for 7-bromohomotrypargine (5).10 Analysis of 1H and 13C NMR chemical shifts, 1H−1H spin systems determined by COSY, and 1H−13C connectivities determined by multiplicity-edited HSQC and HMBC NMR experiments rapidly established that 2 embodied the same skeleton as 5, but with minor differences (0.11/0.13 ppm more deshielded) observed in the 1H chemical shifts for H2-10. Differences in 13C chemical shifts between 5 and 2 were also observed, being centered upon the pyrrole ring with Δδ values (δC 2 − δC 5) of −3.7 (C-4a), −4.5 (C-4b), −2.8 (C-8), −1.6 (C-8a), and −0.7 (C-9a). Similar trends in the differences between the corresponding resonances for the β-carboline opacaline A and its N-9 hydroxy analogue opacaline B were observed,10 leading us to conclude that 2 was the N-9 hydroxy analogue of 7bromohomotrypargine, or alternatively it could be thought of as the 1,2,3,4-tetrahydro analogue of opacaline B. While 7bromohomotrypargine (5) was found to be levorotatory (with implied 1S configuration),10 2 exhibited no chiroptical properties (ECD and specific rotation), leading us to the somewhat surprising conclusion that the metabolite was isolated as a racemate. Compound 2 was tested against a chloroquine-resistant strain (FcB1-Colombia) of Plasmodium falciparum and found to exhibit an IC50 value of 3.8 μM (±0.2, n = 3). This value is similar to that reported for the structurally related sponge metabolite (+)-7-bromotrypargine (IC50 5.4 μM, Dd2 chloroquine-resistant)13 and to other fully oxidized β-carboline analogues previously reported by us from P. opacum.10 In
fraction obtained from the original C18 chromatography column was found to be rich in lipids. Repeated C18 chromatography on this fraction using acidified solvents led to the purification of the trifluoroacetate salt of distaminolyne A (1) as a weakly optically active yellow oil. A molecular formula of C17H27NO for 1, requiring five degrees of unsaturation, was established by (+)-HRESIMS. 1H NMR data acquired in CD3OD accounted for 24 nonexchangeable protons, composed of a terminal alkene [δH 5.85 (1H, ddt, J = 17.1, 10.5, 6.5 Hz), 5.08 (1H, ddt, J = 17.1, 1.5, 1.5 Hz), 5.03 (1H, ddt, J = 10.5, 1.5, 1.5 Hz)], three allylic/propargylic methylenes [δH 2.33 (2H), 2.25 (4H)], an oxymethine [δH 3.74 (1H, m)], an aminomethylene [δH 3.01 (1H, dd, J = 12.8, 3.1 Hz), 2.75 (1H, dd, J = 12.8, 9.5 Hz)], and a methylene envelope [δH 1.50 (6H), 1.37 (6H)] (Table 1). Combined analysis of 13C, multiplicity-edited HSQC, and COSY spectra accounted for all 17 carbon resonances and identified the presence of terminal alkene (δC 137.8, δH 5.85; δC 116.3, δH 5.08, 5.03) and 1,2-amino alcohol (δC 46.1, δH 3.01, 2.75; δC 68.8, δH 3.74) moieties in addition to nine alkyl methylenes. Also identified from the 13C NMR data were four quaternary Table 1. NMR Data (CD3OD) for Distaminolyne A (1)a position
δC, type
1
46.1, CH2
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
68.8, CH 36.0, CH2 26.3, CH2 30.5,c CH2 30.1c, CH2 29.8c, CH2 29.5c, CH2 19.6, CH2 78.0, C 66.3,d C 66.7,d C 77.1, C 19.6, CH2 33.7, CH2 137.8, CH 116.3, CH2
δH, mult (J in Hz)
HMBCb
3.01, 2.75, 3.74, 1.50, 1.50, 1.37, 1.37, 1.37, 1.50, 2.25,
dd (12.8, 3.1) dd (12.8, 9.5) m m m m m m m m
7 or 8, 10, 11
2.33, 2.25, 5.85, 5.03, 5.08,
m m ddt (17.1, 10.5, 6.5) ddt (10.5, 1.5, 1.5) ddt (17.1, 1.5, 1.5)
12, 13, 15 13, 14, 16, 17 15 15 15
2, 3
a1
H (400 MHz), 13C (100 MHz). bHMBC correlations, optimized for 8.3 Hz, reported from the proton resonance to the indicated carbon resonance(s). c,dAssignments are interchangeable. B
DOI: 10.1021/acs.jnatprod.5b00770 J. Nat. Prod. XXXX, XXX, XXX−XXX
Journal of Natural Products
Note
(3.39), 226 (3.01), 240 (2.98), 253 (2.95), 267 (2.93), 283 (2.83) nm; IR νmax (ATR) 3406, 2934, 2857, 1681, 1201, 1178, 1136, 801, 722 cm−1; 1H and 13C NMR data, see Table 1; (+)-HRESIMS m/z 284.1987 [M + Na]+ (calcd for C17H27NNaO, 284.1985). 7-Bromo-N-hydroxyhomotrypargine (2): yellow oil; [α]22D 0, [α]22633 0 (c 0.55, MeOH), [α]22436 +1 (c 0.28, MeOH); UV (MeOH) λmax (log ε) 236 (4.68), 295 (4.02) nm; ECD (c = 3.84 × 10−4 M, MeOH, λ [nm] (Δε)) no Cotton effects were observed over the range λ = 200−400 nm; 1H NMR (CD3OD, 500 MHz) δ 7.55 (1H, d, J = 1.8 Hz, H-8), 7.42 (1H, d, J = 8.6 Hz, H-5), 7.20 (1H, dd, J = 8.6, 1.8 Hz, H-6), 4.78 (1H, dd, J = 8.2, 3.6 Hz, H-1), 3.65 (1H, dt, J = 12.8, 6.3 Hz, H-3a), 3.51 (1H, dt, J = 12.8, 6.0 Hz, H-3b), 3.24 (2H, br t, J = 6.6 Hz, H2-13), 3.06 (2H, dd, J = 6.3, 6.0 Hz, H2-4), 2.37 (1H, m, H10a), 2.13 (1H, m, H-10b), 1.78−1.62 (4H, m, H2-11 and H2-12); 13C NMR (CD3OD, 125 MHz) δ 158.7 (C-15), 137.5 (C-8a), 130.3 (C9a), 124.2 (C-6), 122.0 (C-4b), 120.9 (C-5), 117.5 (C-7), 112.5 (C8), 104.1 (C-4a), 53.0 (C-1), 42.1 (C-13), 41.2 (C-3), 32.4 (C-10), 29.6 (C-12), 23.6 (C-11), 19.1 (C-4); (+)-HRESIMS m/z 380.1059 [M + H]+ (calcd for C16H2379BrN5O, 380.1080), 382.1050 [M + H]+ (calcd for C16H2381BrN5O, 382.1066). Benzoylated Analogues 3 and 4. To a solution of distaminolyne A (4.6 mg, 0.018 mmol) and DMAP (0.2 mg, 0.0018 mmol) in pyridine (0.4 mL) was added benzoyl chloride (27 μL, 0.23 mmol). The reaction was stirred at 50 °C for 64 h, concentrated, and purified by silica gel column chromatography (hexane to hexane/EtOAc, 7:3) to afford 3 (1.0 mg, 16% yield) and 4 (0.7 mg, 8% yield), both as colorless oils. N-(2-Hydroxyheptadeca-16-en-10,12-diyn-1-yl)benzamide (3): [α]17D −4 (c 0.17, CHCl3); Rf (hexanes/EtOAc, 4:1) 0.10; IR νmax (ATR) 3356, 2923, 2853, 1725, 1633, 1274, 1120, 1073, 705 cm−1; 1H NMR (CDCl3, 500 MHz) δ 7.79 (2H, m, H-4′), 7.51 (1H, m, H-6′), 7.44 (2H, m, H-5′), 6.56 (1H, br s, NH-1′), 5.84 (1H, m, H-16), 5.06 (2H, m, H2-17), 3.83 (1H, br s, H-2), 3.72 (1H, ddd, J = 14.0, 6.3, 3.0 Hz, H-1a), 3.32 (1H, ddd, J = 14.0, 7.8, 5.2 Hz, H-1b), 2.34 (2H, m, H2-14), 2.30−2.22 (4H, m, H2-9 and H2-15), 1.53−1.24 (12H, m, H23 to H2-8); (+)-HRESIMS m/z 388.2261 [M + Na]+ (calcd for C24H31NNaO2, 388.2247). 1-Benzamidoheptadeca-16-en-10,12-diyn-2-yl benzoate (4): [α]17D −12 (c 0.13, CHCl3); Rf (hexanes/EtOAc, 4:1) 0.19; UV (MeOH) λmax (log ε) 229 (3.89), 252 (3.28), 267 (3.19), 283 (3.03) nm; ECD (c = 1.49 × 10−4 M, MeOH, λ [nm] (Δε)) 222 (−6.6), 231 (0), 239 (+6.1); IR νmax (ATR) 3359, 3182, 2922, 2852, 1659, 1632, 1425, 1262, 701 cm−1; 1H NMR (CDCl3, 500 MHz) δ 8.06 (2H, m, H-4′), 7.74 (2H, m, H-3″), 7.58 (1H, m, H-6′), 7.50−7.38 (5H, m, H5″, H-4″, H-5′), 6.70 (1H, br s, NH-1′), 5.84 (1H, m, H-16), 5.30 (1H, m, H-2), 5.06 (2H, m, H2-17), 3.81 (1H, ddd, J = 14.4, 5.4, 3.0 Hz, H-1a), 3.73 (1H, ddd, J = 14.4, 8.4, 5.4 Hz, H-1b), 2.34 (2H, td, J = 7.0, 1.3 Hz, H2-14), 2.27 (2H, t, J = 6.5 Hz, H2-15), 2.22 (2H, t, J = 7.0 Hz, H2-9), 1.83 (1H, m, H-3a), 1.76 (1H, m, H-3b), 1.59−1.24 (10H, m, H2-4 to H2-8); (+)-HRESIMS m/z 492.2524 [M + Na]+ (calcd for C31H35NNaO3, 492.2509). Antiplasmodial Activity Determination. Methods have been previously described.18 Chloroquine was used as the positive control, exhibiting an IC50 of 0.16 ± 0.06 μM (n = 3). Bacterial Growth and MIC/MBC Determination. Escherichia coli 25922 and Staphylococcus aureus XEN36 were grown overnight, at 37 °C with shaking at 200 rpm, in Muller Hinton broth. To determine MIC and MBC the standard microbroth dilution assay was used19 with minor adjustments. Overnight broths were adjusted to give a final concentration of approximately 5 × 105 cfu/mL (confirmed by retrospective plating) in Muller Hinton broth in a 96-well microtiter plate. Mycobacterium tuberculosis BSG001 (M. tuberculosis H37Rv transformed with the bacterial luciferase-encoding vector pMV306hsp + LuxAB + G13 + CDE)20 was grown for 2 weeks at 37 °C with gentle shaking (100 rpm) in Middlebrook 7H9 broth supplemented with Middlebrook ADC enrichment media and glycerol. When needed, kanamycin was used at a concentration of 25 mg/L. During drug testing assays Middlebrook 7H9 medium was prepared without Tween or kanamycin. Test compounds were dissolved in DMSO and added to the bacterial broths in a concentration gradient (64 μg/mL to 1 μg/
microbroth-dilution assays, N-hydroxy metabolite 2 exhibited modest activity toward Staphylococcus aureus XEN36 [MIC (minimum inhibitory concentration) and MBC (minimum bactericidal concentration) values of 32 μg/mL (53 μM)] but was poorly active toward Escherichia coli 25922 (MIC 64 μg/ mL, MBC > 64 μg/mL [106 μM]) and inactive toward Mycobacterium tuberculosis BSG001 (MIC and MBC > 64 μg/ mL [106 μM]). Distaminolyne A (1) exhibited an MIC of 32 μg/mL (85 μM) toward both S. aureus and M. tuberculosis and 64 μg/mL (170 μM) toward E. coli, with corresponding MBC values of 32, 64, and >128 μg/mL, respectively. No effect on bacterial growth or viability was observed for dibenzoyl derivative 4. With regard to the antibacterial activity observed for distaminolyne A, it should be noted that slightly more potent levels (MIC 33−65 μM) of activity were observed for a shorter chain length saturated 2-amino-3-alcohol lipid (3-epixestoaminol C) recently reported from a New Zealand brown alga,14 while shorter chain 2-amino-3-alcohol lipids (crucigasterins B and E) isolated from Pseudodistoma crucigaster exhibited similar levels of activity against E. coli (MIC 50 μg/ mL [196 μM] and 100 μg/mL [360 μM], respectively).7c The biosynthetic precursors of sphingolipids are fatty acid CoA esters and (S)-serine;8 by analogy biosynthesis of 1 would require palmitic acid (C16) and glycine.11,15 The location and extent of unsaturation in 1 would require the actions of fatty acid Δ9, Δ11, and Δ15 desaturases and Δ9 and Δ11 acetylenases (fatty acid numbering), the existence of which in nature are supported by either the structures of unsaturated natural products, isotopic feeding experiments,4 and/or genetic studies.3,16 In summary, our investigation of the chemistry of a New Zealand collection of the ascidian Pseudodistoma sp. has led to the isolation and structural characterization of a new Nhydroxy-1,2,3,4-tetrahydro-β-carboline as well as the first example of an acetylenic 1-amino-2-alcohol lipid.
■
EXPERIMENTAL SECTION
General Experimental Procedures. The majority of the experimental details have been reported elsewhere.17 NMR referencing used proto-deutero solvent signals (CD3OD: δH 3.31, δC 49.00) or tetramethylsilane. ECD spectra were recorded on an Applied Photophysics Pi star spectrophotometer, while optical rotations were recorded on an Autopol IV polarimeter using a 1 dm cell. Animal Material. The ascidian was collected on September 7, 2012, by scuba at a depth of 10 m off Ti Pt., Northland, New Zealand, and kept frozen until used. A voucher specimen of the white/pale yellow-colored ascidian Pseudodistoma opacum is held at the National Institute for Water and Atmospheric Research, Private Bag 14901, Wellington, New Zealand, as NIWA 99203. A color in situ photograph is included in the Supporting Information. Isolation and Purification. The freeze-dried ascidian specimens (dry weight 99.7 g) were extracted repeatedly with MeOH (6 × 200 mL), filtered, and concentrated in vacuo. The combined green solid (11.28 g) was subjected to initial C18 reversed-phase column chromatography using a step gradient of acidified (0.05% TFA) H2O to MeOH. The H2O/TFA and 10% MeOH/H2O/TFA fractions were combined and subjected to C2 chromatography (100% H2O/ TFA) to give a brown gum (196 mg). A fraction of the brown gum (30 mg) was subjected to a second round of C2 column chromatography to give 7-bromo-N-hydroxyhomotrypargine (2) (8.2 mg, 0.054% dry weight). The 75% MeOH/H2O fraction from the initial C18 column was subjected to repeated C18 column chromatography (60% MeOH/ H2O (TFA)) to afford distaminolyne A (1) (4.5 mg, 5 × 10−5% dry weight). Distaminolyne A (1): yellow oil; [α]20D −1 (c 0.44, MeOH); Rf (EtOAc/MeOH, 1:1) 0.04; UV (MeOH) λmax (log ε) 205 (3.37), 215 C
DOI: 10.1021/acs.jnatprod.5b00770 J. Nat. Prod. XXXX, XXX, XXX−XXX
Journal of Natural Products
Note
mL) using doubling dilutions. Untreated controls and DMSO diluent controls were included for each. Plates were incubated overnight at 37 °C. Triplicates of each concentration were tested, and experiments were carried out on three separate occasions. MBC was determined by transferring 5 μL of broth from the MIC wells into 195 μL of fresh media, incubating overnight at 37 °C, and observing growth. No growth indicated there were no viable cells present. Dilutions of cells were also plated out to determine bacterial presence. A reduction of bacterial numbers of a minimum of 3 logs from initial inoculum indicated the MBC value. Rifampicin was used as a positive control, exhibiting MIC/MBC values of 8/8 μg/mL (E. coli), 4/8 ng/mL (S. aureus), and 161/161 ng/mL (M. tuberculosis), respectively.
■
(9) Pearce, A. N.; Appleton, D. R.; Babcock, R. C.; Copp, B. R. Tetrahedron Lett. 2003, 44, 3897−3899. (10) Chan, S. T. S.; Pearce, A. N.; Page, M. J.; Kaiser, M.; Copp, B. R. J. Nat. Prod. 2011, 74, 1972−1979. (11) Searle, P. A.; Molinski, T. F. J. Org. Chem. 1993, 58, 7578−7580. (12) Kawai, M.; Nagai, U.; Katsumi, M. Tetrahedron Lett. 1975, 16, 3165−3166. (13) Davis, R. A.; Duffy, S.; Avery, V. M.; Camp, D.; Hooper, J. N. A.; Quinn, R. J. Tetrahedron Lett. 2010, 51, 583−585. (14) Dasyam, N.; Munkacsi, A. B.; Fadzilah, N. H.; Senanayake, D. S.; O’Toole, R. F.; Keyzers, R. A. J. Nat. Prod. 2014, 77, 1519−1523. (15) Gulavita, N. K.; Scheuer, P. J. J. Org. Chem. 1989, 54, 366−369. (16) Haritos, V. S.; Horne, I.; Damcevski, K.; Glover, K.; Gibb, N.; Okada, S.; Hamberg, M. Nat. Commun. 2012, 3, 1150. (17) Khalil, I. M.; Barker, D.; Copp, B. R. J. Nat. Prod. 2012, 75, 2256−2260. (18) Longeon, A.; Copp, B. R.; Roué, M.; Dubois, J.; Valentin, A.; Petek, S.; Debitus, C.; Bourguet-Kondracki, M.-L. Bioorg. Med. Chem. 2010, 18, 6006−6011. (19) Wiegand, I.; Hilpert, K.; Hancock, R. E. W. Nat. Protoc. 2008, 3, 163−175. (20) Andreu, N.; Zelmer, A.; Fletcher, T.; Elkington, P. T.; Ward, T. H.; Ripoll, J.; Parish, T.; Bancroft, G. J.; Schaible, U.; Robertson, B. D.; Wiles, S. PLoS One 2010, 5, e10777.
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jnatprod.5b00770. Figures S1−S16; color in situ photo of Pseudodistoma opacum, UV−vis, 1H, 13C, COSY, HSQC, HMBC, and HSQC-TOCSY NMR spectra for 1, 1H spectra of derivatives 3 and 4, ECD spectrum of 4, and 1H, 13C, COSY, HSQC, and HMBC NMR spectra for 2 (PDF)
■
AUTHOR INFORMATION
Corresponding Author
*Tel: +64 9 373 7599, ext 88284. E-mail:
[email protected]. nz. Present Address ‡
Molecular Targets Laboratory, Center for Cancer Research, National Cancer Institute, Building 562, Frederick, Maryland 21702, United States. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS We acknowledge funding from the University of Auckland. We thank Prof. T. Brittain for assistance with ECD spectra acquisition, Dr. M. Schmitz for assistance with NMR data acquisition, and Dr. N. Lloyd for MS data.
■
DEDICATION Dedicated to Professors John Blunt and Murray Munro, of the University of Canterbury, for their pioneering work on bioactive marine natural products.
■
REFERENCES
(1) Dembitsky, V. M. Lipids 2006, 41, 883−924. (2) Zhou, Z.-F.; Menna, M.; Cai, Y.-S.; Guo, Y.-W. Chem. Rev. 2015, 115, 1543−1596. (3) Ross, C.; Scherlach, K.; Kloss, F.; Hertweck, C. Angew. Chem., Int. Ed. 2014, 53, 7794−7798. (4) Minto, R. E.; Blacklock, B. J. Prog. Lipid Res. 2008, 47, 233−306. (5) Gavagnin, M.; Castelluccio, F.; Antonelli, A.; Templado, J.; Cimino, G. Lipids 2004, 39, 681−685. (6) Tsukamoto, S.; Kato, H.; Hirota, H.; Fusetani, N. J. Nat. Prod. 1997, 60, 126−130. (7) (a) Perry, N. B.; Blunt, J. W.; Munro, M. H. G. Aust. J. Chem. 1991, 44, 627−633. (b) Hooper, G. J.; Davies-Coleman, M. T.; Coetzee, P. S. Nat. Prod. Lett. 1995, 6, 31−35. (c) Ciavatta, M. L.; Manzo, E.; Nuzzo, G.; Villani, G.; Varcamonti, M.; Gavagnin, M. Tetrahedron 2010, 66, 7533−7538. (8) Stoffel, W. Annu. Rev. Biochem. 1971, 40, 57−82. D
DOI: 10.1021/acs.jnatprod.5b00770 J. Nat. Prod. XXXX, XXX, XXX−XXX
