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Agarwal, V, Blanton JM, Podell S, Taton A, Schorn MA, Busch J, Lin Z, Schmidt EW, Jensen PR, Paul VJ, Biggs JS, Golden JW, Allen EE, Moore BS.  2017.  Metagenomic discovery of polybrominated diphenyl ether biosynthesis by marine sponges. Nat Chem Biol. advance online publication: Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.   10.1038/nchembio.2330   Abstract

Naturally produced polybrominated diphenyl ethers (PBDEs) pervade the marine environment and structurally resemble toxic man-made brominated flame retardants. PBDEs bioaccumulate in marine animals and are likely transferred to the human food chain. However, the biogenic basis for PBDE production in one of their most prolific sources, marine sponges of the order Dysideidae, remains unidentified. Here, we report the discovery of PBDE biosynthetic gene clusters within sponge-microbiome-associated cyanobacterial endosymbionts through the use of an unbiased metagenome-mining approach. Using expression of PBDE biosynthetic genes in heterologous cyanobacterial hosts, we correlate the structural diversity of naturally produced PBDEs to modifications within PBDE biosynthetic gene clusters in multiple sponge holobionts. Our results establish the genetic and molecular foundation for the production of PBDEs in one of the most abundant natural sources of these molecules, further setting the stage for a metagenomic-based inventory of other PBDE sources in the marine environment.

Ahmed, L, Jensen PR, Freel KC, Brown R, Jones AL, Kim BY, Goodfellow M.  2013.  Salinispora pacifica sp nov., an actinomycete from marine sediments. Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology. 103:1069-1078.   10.1007/s10482-013-9886-4   AbstractWebsite

A polyphasic analysis was carried out to clarify the taxonomic status of four marine actinomycete strains that share a phylogenetic relationship and phenotypic characteristics with the genus Salinispora. These strains formed a distinct lineage within the Salinispora 16S rRNA and gyrB trees and were found to possess a range of phenotypic properties and DNA: DNA hybridization values that distinguished them from the type strains of the two validly named species in this genus, Salinispora tropica (CNB-440(T), ATCC BAA-916(T)) and Salinispora arenicola (CNH-643(T), ATCC BAA-917(T)). The combined genotypic and phenotypic data support this conclusion. It is proposed that the strains be designated as Salinispora pacifica sp. nov., the type strain of which is CNR-114(T) (DSMZ YYYYT = KACC 17160(T)).

Alvarez-Mico, X, Jensen PR, Fenical W, Hughes CC.  2013.  Chlorizidine, a Cytotoxic 5H-Pyrrolo 2,1-a isoindol-5-one-Containing Alkaloid from a Marine Streptomyces sp. Organic Letters. 15:988-991.   10.1021/ol303374e   AbstractWebsite

Cultivation of an obligate marine Streptomyces strain has provided the cytotoxic natural product chlorizidine A. X-ray crystallographic analysis revealed that the metabolite is composed of a chlorinated 2,3-dihydropyrrolizine ring attached to a chlorinated 5H-pyrrolo[2,1-a]isoindol-5-one. The carbon stereocenter in the dihydropyrrolizine is S-configured. Remarkably, the 5H-pyrrolo[2,1-a]isoindol-5-one moiety has no precedence in the field of natural products. The presence of this ring system, which was demonstrated to undergo facile nucleophilic substitution reactions at the activated carbonyl group, is essential to the molecule's cytotoxicity against HCT-116 human colon cancer cells.

Amos, GCA, Awakawa T, Tuttle RN, Letzel AC, Kim MC, Kudo Y, Fenical W, Moore BS, Jensen PR.  2017.  Comparative transcriptomics as a guide to natural product discovery and biosynthetic gene cluster functionality. Proceedings of the National Academy of Sciences of the United States of America. 114:E11121-E11130.   10.1073/pnas.1714381115   AbstractWebsite

Bacterial natural products remain an important source of new medicines. DNA sequencing has revealed that a majority of natural product biosynthetic gene clusters (BGCs) maintained in bacterial genomes have yet to be linked to the small molecules whose biosynthesis they encode. Efforts to discover the products of these orphan BGCs are driving the development of genome mining techniques based on the premise that many are transcriptionally silent during normal laboratory cultivation. Here, we employ comparative transcriptomics to assess BGC expression among four closely related strains of marine bacteria belonging to the genus Salinispora. The results reveal that slightly more than half of the BGCs are expressed at levels that should facilitate product detection. By comparing the expression profiles of similar gene clusters in different strains, we identified regulatory genes whose inactivation appears linked to cluster silencing. The significance of these subtle differences between expressed and silent BGCs could not have been predicted a priori and was only revealed by comparative transcriptomics. Evidence for the conservation of silent clusters among a larger number of strains for which genome sequences are available suggests they may be under different regulatory control from the expressed forms or that silencing may represent an underappreciated mechanism of gene cluster evolution. Coupling gene expression and metabolomics data established a bioinformatic link between the salinipostins and their associated BGC, while genetic manipulation established the genetic basis for this series of compounds, which were previously unknown from Salinispora pacifica.

Asolkar, RN, Singh A, Jensen PR, Aalbersberg W, Carte BK, Feussner KD, Subramani R, DiPasquale A, Rheingold AL, Fenical W.  2017.  Marinocyanins, cytotoxic bromo-phenazinone meroterpenoids from a marine bacterium from the streptomycete Glade MAR4. Tetrahedron. 73:2234-2241.   10.1016/j.tet.2017.03.003   AbstractWebsite

Six cytotoxic and antimicrobial metabolites of a new bromo-phenazinone class, the marinocyanins A-F (1-6), were isolated together with the known bacterial metabolites 2-bromo-1-hydroxyphenazine (7), lavanducyanin (8, WS-9659A) and its chlorinated analog WS-9659B (9). These metabolites were purified by bioassay-guided fractionation of the extracts of our MAR4 marine actinomycete strains CNS-284 and CNY-960. The structures of the new compounds were determined by detailed spectroscopic methods and marinocyanin A (1) was confirmed by crystallographic methods. The marinocyanins represent the first bromo-phenazinones with an N-isoprenoid substituent in the skeleton. Marinocyanins A-F show strong to weak cytotoxicity against HCT-116 human colon carcinoma and possess modest antimicrobial activities against Staphylococcus aureus and amphotericin-resistant Candida albicans. (C) 2017 Elsevier Ltd. All rights reserved.

Asolkar, RN, Jensen PR, Asolkar RN, Fenical W.  2006.  Daryamides A-C, weakly cytotoxic polyketides from a marine-derived actinomycete of the genus Streptomyces strain CNQ-085. Journal of Natural Products. 69:1756-1759.   10.1021/np0603828   AbstractWebsite

In the course of our continuing search for new antitumor-antibiotics from marine-derived actinomycete bacteria, four new cytotoxic compounds, designated as daryamides A (1), B ( 2), and C ( 3) and (2E, 4E)-7- methylocta- 2,4-dienoic acid amide (4), were isolated from the culture broth of a marine-derived Streptomyces strain CNQ-085. The structures of these new compounds were assigned by detailed interpretation of spectroscopic data. The relative configuration of 1 was determined by comprehensive NMR analysis, while the absolute configuration of 1 was determined as 4S,5R using the modified Mosher method. The daryamides show weak to moderate cytotoxic activity against the human colon carcinoma cell line HCT-116 and very weak antifungal activities against Candida albicans.

Asolkar, RN, Freel KC, Jensen PR, Fenical W, Kondratyuk TP, Park EJ, Pezzuto JM.  2009.  Arenamides A-C, Cytotoxic NF kappa B Inhibitors from the Marine Actinomycete Salinispora arenicola. Journal of Natural Products. 72:396-402.   10.1021/np800617a   AbstractWebsite

Three new cyclohexadepsipeptides, arenamides A-C (1-3), were isolated from the fermentation broth of a marine bacterial strain identified as Salinispora arenicola. The planar structures of these compounds were assigned by detailed interpretation of NMR and MS/MS spectroscopic data. The absolute configurations of the amino acids, and those of the chiral centers on the side chain, were established by application of the Marfey and modified Mosher methods. The effect of arenamides A and B on NF kappa B activity was studied with stably transfected 293/NF kappa B-Luc human embryonic kidney cells induced by treatment with tumor necrosis factor (TNF). Arenamides A (1) and B (2) blocked TNF-induced activation in a dose- and time-dependent manner with IC(50) values of 3.7 and 1.7 mu M, respectively. In addition, the compounds inhibited nitric oxide (NO) and prostaglandin E(2) (PGE(2)) production with lipopolysaccharide (LPS)-induced RAW 264.7 macrophages. Moderate cytotoxicity was observed with the human colon carcinoma cell line HCT-116, but no cytotoxic effect was noted with cultured RAW cells. Taken together, these data suggest that the chemoprevention and anti-inflammatory characteristics of arenamides A and B warrant further investigation.

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Becerril-Espinosa, A, Freel KC, Jensen PR, Soria-Mercado IE.  2013.  Marine Actinobacteria from the Gulf of California: diversity, abundance and secondary metabolite biosynthetic potential. Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology. 103:809-819.   10.1007/s10482-012-9863-3   AbstractWebsite

The Gulf of California is a coastal marine ecosystem characterized as having abundant biological resources and a high level of endemism. In this work we report the isolation and characterization of Actinobacteria from different sites in the western Gulf of California. We collected 126 sediment samples and isolated on average 3.1-38.3 Actinobacterial strains from each sample. Phylogenetic analysis of 136 strains identified them as members of the genera Actinomadura, Micromonospora, Nocardiopsis, Nonomuraea, Saccharomonospora, Salinispora, Streptomyces and Verrucosispora. These strains were grouped into 26-56 operational taxonomic units (OTUs) based on 16S rRNA gene sequence identities of 98-100 %. At 98 % sequence identity, three OTUs appear to represent new taxa while nine (35 %) have only been reported from marine environments. Sixty-three strains required seawater for growth. These fell into two OTUs at the 98 % identity level and include one that failed to produce aerial hyphae and was only distantly related (a parts per thousand currency sign95.5 % 16S identity) to any previously cultured Streptomyces sp. Phylogenetic analyses of ketosynthase domains associated with polyketide synthase genes revealed sequences that ranged from 55 to 99 % nucleotide identity to experimentally characterized biosynthetic pathways suggesting that some may be associated with the production of new secondary metabolites. These results indicate that marine sediments from the Gulf of California harbor diverse Actinobacterial taxa with the potential to produce new secondary metabolites.

Belofsky, GN, Anguera M, Jensen PR, Fenical W, Kock M.  2000.  Oxepinamides A-C and fumiquinazolines H-I: Bioactive metabolites from a marine isolate of a fungus of the genus Acremonium. Chemistry-a European Journal. 6:1355-1360.   10.1002/(sici)1521-3765(20000417)6:8<1355::aid-chem1355>3.3.co;2-j   AbstractWebsite

Three new oxepin-containing natural products (1-3) and two new fumiquinazoline metabolites (4-5) have been isolated from organic extracts of the culture broth and mycelia of an Acremonium sp., a fungus obtained from the surface of the Caribbean tunicate Ectcinascidia turbinata. The structures of the five compounds were determined through extensive analysis of 1D- and 2D-NMR data, and mass spectrometry. Compound 1 exhibited good anti-inflammatory activity in a topical RTX-induced mouse ear edema assay. Compounds 4 and 5 exhibited weak antifungal activity toward Candida albicans in a broth microdilution assay.

Belofsky, GN, Jensen PR, Fenical W.  1999.  Sansalvamide: A new cytotoxic cyclic depsipeptide produced by a marine fungus of the genus Fusarium. Tetrahedron Letters. 40:2913-2916.   10.1016/s0040-4039(99)00393-7   AbstractWebsite

A new cyclic pentadepsipeptide, sansalvamide (1), has been isolated from organic extracts of the mycelium of a fungus of the genus Fusarium collected from the surface of the seagrass Halodule wrightii. The structure of 1 was determined through extensive analysis of 1D and 2D NMR data. Sansalvamide exhibited selective in vitro cytotoxicity toward COLO 205 colon and SK-MEL-2 melanoma cancer cell lines. (C) 1999 Elsevier Science Ltd. All rights reserved.

Belofsky, GN, Jensen PR, Renner MK, Fenical W.  1998.  New cytotoxic sesquiterpenoid nitrobenzoyl esters from a marine isolate of the fungus Aspergillus versicolor. Tetrahedron. 54:1715-1724.   10.1016/s0040-4020(97)10396-9   AbstractWebsite

Four new sesquiterpenoid nitrobenzoyl esters (1-4) have been isolated from organic extracts of the culture broth and mycelia of Aspergillus versicolor, a fungus isolated from the surface of the Caribbean green alga Penicillus capitatus. The structures of the four compounds were determined through extensive analysis of H-1 NMR, C-13 NMR, HMQC, and HMBC data. 9 alpha,14-Dihydroxy-6 beta-p-nitrobenzoylcinnamolide (1) displayed significant cytoxicity against HCT-116 human colon carcinoma cells in vitro and exhibited moderately selective cytotoxicity toward a panel of renal tumor cell lines. (C) 1998 Elsevier Science Ltd. Ali rights reserved.

Boehler, M, Jensen PR, Fenical W.  1997.  Bahamamide, an unusual cyclic bis-amide produced by an undescribed marine bacterium. Natural Product Letters. 10:75-78.   10.1080/10575639708043699   AbstractWebsite

An unusual 12-membered ring bis-amide, bahamamide (1), has been isolated from the culture broth of an undescribed gram-negative marine bacterial strain, CNE-852, isolated from a sediment sample collected in the Bahama Islands. The structure of bahamamide was assigned by interpretation of combined spectral data.

Boonlarppradab, C, Kauffman CA, Jensen PR, Fenical W.  2008.  Marineosins A and B, Cytotoxic Spiroaminals from a Marine-Derived Actinomycete. Organic Letters. 10:5505-5508.   10.1021/ol8020644   AbstractWebsite

Two novel spiroaminals, marineosins A and B (1, 2), containing two pyrrole functionalities, were isolated from cultures of a marine sediment-derived actinomycete related to the genus Streptomyces. The marineosins, which appear to be derived from unknown modifications of prodigiosin-like pigment pathways, showed significant inhibition of human colon carcinoma (HCT-116) in an in vitro assay (IC(50) = 0.5 mu M for marineosin A) and selective activities in diverse cancer cell types.

Bruns, H, Crusemann M, Letzel AC, Alanjary M, McInerney JO, Jensen PR, Schulz S, Moore BS, Ziemert N.  2018.  Function-related replacement of bacterial siderophore pathways. Isme Journal. 12:320-329.   10.1038/ismej.2017.137   AbstractWebsite

Bacterial genomes are rife with orphan biosynthetic gene clusters (BGCs) associated with secondary metabolism of unrealized natural product molecules. Often up to a tenth of the genome is predicted to code for the biosynthesis of diverse metabolites with mostly unknown structures and functions. This phenomenal diversity of BGCs coupled with their high rates of horizontal transfer raise questions about whether they are really active and beneficial, whether they are neutral and confer no advantage, or whether they are carried in genomes because they are parasitic or addictive. We previously reported that Salinispora bacteria broadly use the desferrioxamine family of siderophores for iron acquisition. Herein we describe a new and unrelated group of peptidic siderophores called salinichelins from a restricted number of Salinispora strains in which the desferrioxamine biosynthesis genes have been lost. We have reconstructed the evolutionary history of these two different siderophore families and show that the acquisition and retention of the new salinichelin siderophores co- occurs with the loss of the more ancient desferrioxamine pathway. This identical event occurred at least three times independently during the evolution of the genus. We surmise that certain BGCs may be extraneous because of their functional redundancy and demonstrate that the relative evolutionary pace of natural pathway replacement shows high selective pressure against retention of functionally superfluous gene clusters.

Bucarey, SA, Penn K, Paul L, Fenical W, Jensen PR.  2012.  Genetic Complementation of the Obligate Marine Actinobacterium Salinispora tropica with the Large Mechanosensitive Channel Gene mscL Rescues Cells from Osmotic Downshock. Applied and Environmental Microbiology. 78:4175-4182.   10.1128/aem.00577-12   AbstractWebsite

Marine actinomycetes in the genus Salinispora fail to grow when seawater is replaced with deionized (DI) water in complex growth media. While bioinformatic analyses have led to the identification of a number of candidate marine adaptation genes, there is currently no experimental evidence to support the genetic basis for the osmotic requirements associated with this taxon. One hypothesis is that the lineage-specific loss of mscL is responsible for the failure of strains to grow in media prepared with DI water. The mscL gene encodes a conserved transmembrane protein that reduces turgor pressure under conditions of acute osmotic downshock. In the present study, the mscL gene from a Micromonospora strain capable of growth on media prepared with DI water was transformed into S. tropica strain CNB-440. The single-copy, chromosomal genetic complementation yielded a recombinant Salinispora mscL(+) strain that demonstrated an increased capacity to survive osmotic downshock. The enhanced survival of the S. tropica transformant provides experimental evidence that the loss of mscL is associated with the failure of Salinispora spp. to grow in low-osmotic-strength media.

Buchanan, GO, Williams PG, Feling RH, Kauffman CA, Jensen PR, Fenical W.  2005.  Sporolides A and B: Structurally unprecedented halogenated macrolides from the marine actinomycete Salinispora tropica. Organic Letters. 7:2731-2734.   10.1021/ol050901i   AbstractWebsite

Analysis of the fermentation broth of a strain of the marine actinomycete Salinispora tropica has led to the isolation of two unprecedented macrolides, sporolides A (1) and B (2). The structures and absolute stereochemistries of both metabolites were elucidated using a combination of NMR spectroscopy and X-ray crystallography.

Bugni, TS, Woolery M, Kauffman CA, Jensen PR, Fenical W.  2006.  Bohemamines from a marine-derived Streptomyces sp. Journal of Natural Products. 69:1626-1628.   10.1021/np0602721   AbstractWebsite

Investigation of the culture extracts of a marine-derived Streptomyces sp. led to the isolation of three new bohemamine-type pyrrolizidine alkaloids, bohemamine B (1), bohemamine C (2), and 5-chlorobohemamine C (3). The structures were elucidated using NMR methods, and the relative stereochemistry was determined using double-pulsed-field-gradient spin echo (DPFGSE) NOE studies.

Busch, J, Agarwal V, Schorn M, Machado H, Moore BS, Rouse GW, Gram L, Jensen PR.  2019.  Diversity and distribution of the bmp gene cluster and its Polybrominated products in the genus Pseudoalteromonas. Environmental Microbiology. 21:1575-1585.   10.1111/1462-2920.14532   AbstractWebsite

The production of pentabromopseudilin and related brominated compounds by Pseudoalteromonas spp. has recently been linked to the bmp biosynthetic gene cluster. This study explored the distribution and evolutionary history of this gene cluster in the genus Pseudoalteromonas. A phylogeny of the genus revealed numerous clades that do not contain type strains, suggesting considerable species level diversity has yet to be described. Comparative genomics revealed four distinct versions of the gene cluster distributed among 19 of the 101 Pseudoalteromonas genomes examined. These were largely localized to the least inclusive clades containing the Pseudoalteromonas luteoviolacea and Pseudoalteromonas phenolica type strains and show clear evidence of gene and gene cluster loss in certain lineages. Bmp gene phylogeny is largely congruent with the Pseudoalteromonas species phylogeny, suggesting vertical inheritance within the genus. However, the gene cluster is found in three different genomic environments suggesting either chromosomal rearrangement or multiple acquisition events. Bmp conservation within certain lineages suggests the encoded products are highly relevant to the ecology of these bacteria.

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Castro-Falcon, G, Millan-Aguinaga N, Roullier C, Jensen PR, Hughes CC.  2018.  Nitrosopyridine probe to detect polyketide natural products with conjugated alkenes: Discovery of novodaryamide and nocarditriene. Acs Chemical Biology. 13:3097-3106.   10.1021/acschembio.8b00598   AbstractWebsite

An optimized nitroso-based probe that facilitates the discovery of conjugated alkene-containing natural products in unprocessed extracts was developed. It chemoselectively reacts with conjugated olefins via a nitroso-Diels-Alder cyclization to yield derivatives with a distinct chromophore and an isotopically unique bromine atom that can be rapidly identified using liquid chromatography/mass spectrometry and a bioinformatics tool called MeHaloCoA (Marine Halogenated Compound Analysis). The probe is ideally employed when genome-mining techniques identify strains containing polyketide gene clusters with two or more repeating KS-AT-DH-KR-ACP domain sequences, which are required for the biosynthesis of conjugated alkenes. Comparing the reactivity and spectral properties of five brominated arylnitroso reagents with model compounds spiramycin, bufalin, rapamycin, and rifampicin led to the identification of 5-bromo-2-nitrosopyridine as the most suitable probe structure. The utility of the dienophile probe was then demonstrated in bacterial extracts. Tylactone, novodaryamide and daryamide A, piperazimycin A, and the saccharamonopyrones A and B were cleanly labeled in extracts from their respective bacterial producers, in high regioselectivity but with varying degrees of diastereoselectivity. Further application of the method led to the discovery of a new natural product called nocarditriene, containing an unprecedented epoxy-2,3,4,5-tetrahydropyridine structure, from marine-derived Nocardiopsis strain CNY-503.

Cheng, XC, Jensen PR, Fenical W.  1999.  Arenaric acid, a new pentacyclic polyether produced by a marine bacterium (Actinomycetales). Journal of Natural Products. 62:605-607.   10.1021/np9801357   AbstractWebsite

Arenaric acid (Pa), a new pentacyclic polyether related to the antibiotics K-41A and oxolonomycin, was isolated as its sodium salt (Ib) from the culture broth of an estuarine bacterial isolate of the genus Streptomyces. The structure of arenaric acid was established by spectroscopic methods involving comprehensive 2D NMR measurements.

Cheng, XC, Jensen PR, Fenical W.  1999.  Luisols A and B, new aromatic tetraols produced by an estuarine marine bacterium of the genus Streptomyces (Actinomycetales). Journal of Natural Products. 62:608-610.   10.1021/np980415m   AbstractWebsite

Luisols A (1) and B (2), two new aromatic tetraols, have been isolated from the cultivation broth of an estuarine marine actinomycete of the genus Streptomyces (strain #CNH-370). The structures of luisols A and B were assigned by combined spectroscopic methods, including extensive 2D NMR experiments. Luisol A appears related to the anthraquinone antibiotics of the granaticin class, while the structure of luisol B contains the rare epoxynaphtho[2,3c]furan, a structural feature found in only one natural product, the fungal metabolite anthrinone.

Cheng, YB, Jensen PR, Fenical W.  2013.  Cytotoxic and antimicrobial napyradiomycins from two marine-derived streptomyces strains. European Journal of Organic Chemistry. :3751-3757.   10.1002/ejoc.201300349   AbstractWebsite

The cancer-cell-cytotoxicity-guided fractionation of the acetone extracts of two cultured marine-derived Streptomyces strains belonging to the MAR4 group yielded six new napyradiomycins, compounds A-F (1-6), together with three known compounds, napyradiomycins B2-B4 (7-9). Napyradiomycins 1-4 are new members of the napyradiomycin C-type meroterpenoids, which possess a linear monoterpene bridge between C-7 and C-10a. Compound 4 has an additional tetrahydropyran ring fused to the phenol moiety. Compounds 5-9 are related to the napyradiomycin B-type meroterpenoids. The structures of all new compounds were assigned by interpretation of 1D and 2D NMR, MS, and other spectroscopic data. The relative configurations were assigned based upon interpretation of ROESY 2D NMR experiments. The cytotoxicity of 1-9 against the human colon carcinoma cell line HCT-116 and their antibacterial activities against methicillin-resistant Staphylococcus aureus (MRSA) are presented.

Cho, JY, Kwon HC, Williams PG, Kauffman CA, Jensen PR, Fenical W.  2006.  Actinofuranones A and B, polyketides from a marine-derived bacterium related to the genus Streptomyces (Actinomycetales). Journal of Natural Products. 69:425-428.   10.1021/np050402q   AbstractWebsite

Two new polyketides, actinofuranones A (1) and B (2), were isolated from the culture extract of a marine-derived Streptomyces strain designated CNQ766. The structures of 1 and 2 were elucidated by interpretation of NMR and other spectroscopic data and by chemical derivatization. The relative stereochemistries of these new molecules were assigned on the basis of analysis of NOE data and vicinal H-1-H-1 coupling constants, while the absolute configurations of the asymmetric centers were determined using the modified Mosher's method.

Cho, JY, Kwon HC, Williams PG, Jensen PR, Fenical W.  2006.  Azamerone, a terpenoid phthalazinone from a marine-derived bacterium related to the genus Streptomyces (actinomycetales). Organic Letters. 8:2471-2474.   10.1021/ol060630r   AbstractWebsite

A novel meroterpenoid, azamerone, was isolated from the saline culture of a new marine-derived bacterium related to the genus Streptomyces. Azamerone is composed of an unprecedented chloropyranophthalazinone core with a 3-chloro-6-hydroxy-2,2,6-trimethylcyclohexylmethyl side chain. The structure was rigorously determined by NMR spectroscopy and X-ray crystallography. A possible biosynthetic origin of this unusual ring system is proposed.