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The structures of five new natural products (GB 27–GB 31, 1–5), isolated as minor components from the bark of Galbulimima baccata, have been determined by 2D NMR spectroscopy in combination with DFT calculations. Among the alkaloids, GB 31 (5) belongs to Class I, GB 27 (1) and 28 (2) belong to Class II, and GB 30 (4) belongs to Class III GB alkaloids. GB 31 is the first non-nitrogen-containing GB “alkaloid”, being a biosynthetic oxidation product of himbacine, himandravine, or himbeline. GB 29 (3) has an entirely new natural product scaffold but belongs to Class IV (miscellaneous alkaloids). The isolation of a new Galbulimimascaffold has revealed a new pathway in the biosynthesis of the GB alkaloids. The new molecules isolated have shed further light on the biogenetic relationship among these structurally unique and complex groups of alkaloids. We present, for the first time, a unified biogenesis for the GB alkaloids that were first isolated in the 1950s and now number over 40 examples. This work also brings full circle the story of Galbulimimaalkaloids. A life-long project of Wal Taylor involving one of his first students (Lew Mander) and one of his last students (Peter Karuso), a story stretching over six decades, has come to a final conclusion.

The tricyclic scaffold of the bacterial polyketide enterocin was recently shown to undergo stereodiversification through a series of abiotic isomerizations, described metaphorically as a “ballet of isomers”. However, some confusion remains regarding the exact nature of these interconversions, with two independent reports proposing different reaction mechanisms and intermediates. Herein, we have rechoreographed enterocin’s ballet of isomers to provide a unified mechanism and revised the structures reported for enterocins C, D, and F.

Cultivation and extraction of the fungus Talaromyces stipitatusled to the isolation of five new oxyphenalenone–amino acid hybrids, which were named talauxins E, Q, V, L, and I based on the corresponding one-letter amino acid codes, along with their putative biosynthetic precursor, duclauxin. The rapid reaction of duclauxin with amino acids to produce talauxins was demonstrated in vitro and exploited to generate a small library of natural and unnatural talauxins. Talauxin V was shown to undergo spontaneous elimination of methyl acetate to yield the corresponding neoclauxin scaffold. This process was modeled using density functional theory calculations, revealing a dramatic change in conformation resulting from the synelimination of methyl acetate.

A structurally locked green fluorescent protein (GFP) chromophore with a phenyl group at C(2) of the imidazolone has been synthesized. Rotation around the exocyclic double bond is hindered, resulting in room-temperature fluorescence. The quantum yield in water is 500 times greater than that of unlocked analogues. Unlike the methyl-substituted analogue, the phenyl analogue exhibits a dual emission (cyan and red) that can be used for ultrasensitive ratiometric measurements and fluorescence microscopy. To explain this dual emission, DFT calculations were carried out along with fluorescence upconversion experiments. The Z-isomer was found to be emissive, while the origin of the dual emission was dependent on the phenyl group in the Z-isomer, which stabilizes the Franck–Condon state, resulting in a cyan fluorescence, while the zwitterionic tautomer fluoresces red. These results bring important new insights into the photophysics of the GFP chromophore and provide a new scaffold capable of dual emission with utility in biotechnology.

Artemisinins are the most potent and safe antimalarials available. Despite their clinical potential, no human target for the artemisinins is known. The unbiased interrogation of several human cDNA libraries, displayed on bacteriophage T7, revealed a single human target of artesunate; the intrinsically disordered Bcl-2 antagonist of cell death promoter (BAD). We show that artesunate inhibits the phosphorylation of BAD, thereby promoting the formation of the proapoptotic BAD/Bcl-xL complex and the subsequent intrinsic apoptotic cascade involving cytochrome c release, PARP cleavage, caspase activation, and ultimately cell death. This unanticipated role of BAD as a possible drug target of artesunate points to direct clinical exploitation of artemisinins in the Bcl-xL life/death switch and that artesunate’s anticancer activity is, at least in part, independent of reactive oxygen species.

Chemical investigation of an Australian fungus, Aspergillus banksianus, led to the isolation of the major metabolite banksialactone A (1), eight new isochromanones, banksialactones B–I (2–9), two new isocoumarins, banksiamarins A and B (10and 11), and the reported compounds, clearanol I (12), dothideomynone A (13), questin (14), and endocrocin (15). The structures of 1–11were established by NMR spectroscopic data analysis, and the absolute configurations were determined from optical rotations and ECD spectra in conjunction with TD-DFT calculations. The secondary metabolite profile of A. banksianusis unusual, with the 11 most abundant metabolites belonging to a single isochromanone class. Conjugation of 1with endocrocin, 5-methylorsellinic acid, 3,5-dimethylorsellinic acid, mercaptolactic acid, and an unknown methylthio source gave rise to five unprecedented biosynthetic hybrids, 5–9. The isolated compounds were tested for cytotoxicity, antibacterial, and antifungal activities, with hybrid metabolites 7–9displaying weak cytotoxic and antibiotic activities.

The isolation of bromotyrosine alkaloids, some of which are enantiomers of previously isolated compounds, has highlighted a possible enantiodivergence in their biosynthesis. Two new (1, 2) and six known bromotyrosine alkaloids (4–9), and the enantiomer (10) of a known compound, have been isolated from a Western Australian marine sponge, Pseudoceratinacf. verrucosa. The compounds inhibited the growth of multidrug-resistant and methicillin-resistant Staphylococcus aureuswith comparable activity to vancomycin. In addition, one possible artifact of extraction (3) containing an ethoxy group was isolated. From analysis of the known bromotyrosine alkaloids, a biogenesis is proposed that explains the formation of antipodal natural products within this family of sponges.

Epicocconone is a heterocyclic natural product from the fungus Epicoccum nigrumthat fluoresces weakly in the green (520 nm). However, cells exposed to epicocconone rapidly absorb the dye and become bright orange fluorescent because the natural product reacts reversibly with proteins. The orange fluorescence is enhanced in lipophilic environments, allowing the visualization of membranous organelles and lipid rafts but does not stain oligonucleotides. As the unconjugated dye has no orange fluorescence, there is no need to wash out the excess fluorophore. Epicocconone is a neutral, non-toxic, small molecule that appears to diffuse readily into live of fixed cells without the need for permeabilization. These features enable the real-time imaging of live cells and the study of organelle movements. Cells stained with epicocconone are excitable by common lasers (UV, 405, 488, and 532 nm) and its long Stokes' shift allows multiplexing applications with more common short Stokes' fluorophores using a single light source.Epicocconone is a heterocyclic natural product from the fungus Epicoccum nigrumthat fluoresces weakly in the green (520 nm). However, cells exposed to epicocconone rapidly absorb the dye and become bright orange fluorescent because the natural product reacts reversibly with proteins. The orange fluorescence is enhanced in lipophilic environments, allowing the visualization of membranous organelles and lipid rafts but does not stain oligonucleotides. As the unconjugated dye has no orange fluorescence, there is no need to wash out the excess fluorophore. Epicocconone is a neutral, non-toxic, small molecule that appears to diffuse readily into live of fixed cells without the need for permeabilization. These features enable the real-time imaging of live cells and the study of organelle movements. Cells stained with epicocconone are excitable by common lasers (UV, 405, 488, and 532 nm) and its long Stokes' shift allows multiplexing applications with more common short Stokes' fluorophores using a single light source.

Epicocconone is the active ingredient in Deep Purple Total Protein Stain and responsible for the apparent noncovalent staining of proteins in polyacrylamide gel and electroblots. Reaction of epicocconone with amines has shown that epicocconone reacts reversibly with primary amines to produce a highly fluorescent enamine that is readily hydrolyzed by base or strong acid such as in conditions used in post-electrophoretic analysis such as peptide mass fingerprinting or Edman degradation.

Chemical genetics and reverse chemical genetics parallel classical genetics but target genes at the protein level and have proven useful in recent years for screening combinatorial libraries for compounds of biological interest. However, the performance of combinatorial chemistry in filling pharmaceutical pipelines has been lower than anticipated and the tide may be turning back to Nature in the search for new drug candidates. Even though diversity oriented synthesis is now producing molecules that are natural product-like in terms of size and complexity, these molecules have not evolved to interact with biomolecules. Natural products, on the other hand, have evolved to interact with biomolecules, which is why so many can be found in pharmacopoeias. However, the cellular targets and modes of action of these fascinating compounds are seldom known, hindering the drug development process. This review focuses on the emergence of chemical proteomics and reverse chemical proteomics as tools for the discovery of cellular receptors for natural products, thereby generating protein / ligand pairs that will prove useful in identifying new drug targets and new biologically active small molecule scaffolds. Such a system-wide approach to identifying new drugable targets and their small molecule ligands will help unblock the pharmaceutical product pipelines by speeding the process of target and lead identification.

The self-association of the DNA metalloprobe Δ-cis-α-[Ru(R,R-picchxnMe₂)(phi)]2+ (α-phi) in aqueous solution has been investigated using 1H NMR spectroscopy and molecular modelling. The concentration dependence of proton chemical shifts of the complex gave initial indications of a self-associated species, while its structural isomer Δ-cis-β-[Ru(R,R-picchxnMe₂)(phi)]2+ (β-phi) showed no such dependence. 2D-COSY and 2D-ROESY experiments were used for the complete assignment of the proton resonances of both isomers and allowed a qualitative determination of the self-association of the α isomer through the detection of intermolecular ROEs. NMR spectroscopy can also be effectively used to differentiate Δ- and Λ-diastereomers. In addition, we show, by pulsed field gradient longitudinal eddy-current delay (PFGLED) NMR spectroscopy, that α-phi self-associates at higher concentrations with an effective molecular weight at 25 mM three times that at 2.5 mM. This apparent oligomerisation was not observed for the β-isomer.

The medicinal plant Bulbine narcissifolia is used by the Basotho, Griqua, and whites of southern Africa for wound healing and as a mild purgative. Extraction of the powdered root has yielded acetosyringone, chrysophanol, knipholone, isoknipholone, 10,7‘-bichrysophanol, and chrysalodin in addition to two new anthraquinone glycosides, knipholone-8-O-β-d-gentiobioside (1) and chrysalodin-10-β-d-gentiobioside (2). NMR spectroscopy was used to elucidate the structures of 1 and 2 and to show that 1 binds weakly to DNA.

A decreased level of fucosylation on certain spore coat proteins of Dictyostelium discoideumalters the permeability of the spore coat. Here the post-translational modifications of a major spore coat protein, SP96, are studied in a wild type strain (X22) and a fucosylation-defective mutant (HU2470). A novel phosphoglycan structure on SP96 of the wild type strain, consisting of Fuc(α1–3)GlcNAc-α-1-P-Ser,was identified by electrospray ionization mass spectrometry and NMR. It was shown using monosaccharide and gas chromatography mass spectrometry analysis that SP96 in the mutant HU2470 contained approximately 20% of wild type levels of fucose, as a result of a missing terminal fucose on the novel glycan structure. The results support previous predictions, based on inhibition studies on different fucose-deficient strains, about the nature of monoclonal antibody epitopes identified by monoclonal antibodies MUD62 and MUD166, which are known to identifyO-linked glycans (Champion, A., Griffiths, K., Gooley, A. A., Gonzalez, B. Y., Gritzali, M., West, C. M., and Williams, K. L. (1995) Microbiology141, 785–797). Quantitative studies on wild type SP96 indicated that there were approximately 60 sites with phosphodiester-linkedN-acetylglucosamine-fucose disaccharide units and a further approximately 20 sites with fucose directly linked to the protein. Over 70% of the serine sites are modified, with less than 1% of these sites as phosphoserine. Threonine and tyrosine residues were not found to be modified.

A decreased level of fucosylation on certain spore coat proteins of Dictyostelium discoideum alters the permeability of the spore coat. Here the post-translational modifications of a major spore coat protein, SP96, are studied in a wild type strain (X22) and a fucosylation-defective mutant (HU2470). A novel phosphoglycan structure on SP96 of the wild type strain, consisting of Fuc(alpha1-3)GlcNAc-alpha-1-P-Ser(,) was identified by electrospray ionization mass spectrometry and NMR. It was shown using monosaccharide and gas chromatography mass spectrometry analysis that SP96 in the mutant HU2470 contained approximately 20% of wild type levels of fucose, as a result of a missing terminal fucose on the novel glycan structure. The results support previous predictions, based on inhibition studies on different fucose-deficient strains, about the nature of monoclonal antibody epitopes identified by monoclonal antibodies MUD62 and MUD166, which are known to identify O-linked glycans (Champion, A., Griffiths, K., Gooley, A. A., Gonzalez, B. Y., Gritzali, M., West, C. M., and Williams, K. L. (1995) Microbiology 141, 785-797). Quantitative studies on wild type SP96 indicated that there were approximately 60 sites with phosphodiester-linked N-acetylglucosamine-fucose disaccharide units and a further approximately 20 sites with fucose directly linked to the protein. Over 70% of the serine sites are modified, with less than 1% of these sites as phosphoserine. Threonine and tyrosine residues were not found to be modified.

The sponge Darwinella sp, contains the known compounds ambliofuran (4) and aplysulphurin (3), and the new compound tetrahydroaplysulphurin-1 (5). Darwinella oxeata collected from various locations around New Zealand, contains aplysulphurin (3) and the new compounds tetrahydroaplysulphurins-1 (5), -2 (6), and -3 (7). Dendrilla rosea which is morphologically similar to the Darwinella sp. above, contains the known compounds ambliofuran (4), aplyroseols-1 (8),-2 (9),-3 (10),-5(11),-6 (12), and -7(15), as well as the new compounds dendrillol-1 (13), dendrillol-2 (14), dendrillol-3 (17) and dendrillol-4 (18). The structure of dendrillol-1 (13) has been confirmed by a single-crystal X-ray determination.

From the red-pink encrusting marine sponge Aplysilla rosea Barrois eight spongian diterpenes were isolated. Aplyroseol-1 was shown by spectroscopic methods to be (5R*,7S*,8R*,9S*,10R*,13S*,14S*,15S*)-15,17-epoxy-17-hydroxy-16-oxospongian-7-yl butyrate (5) and aplyroseol -2 to -6 to be (6)-(10) respectively. Two lactones (11) and (12), ambliofuran and its hexahydro derivative were also identified. A steroid fraction was also isolated.

The sponge Chelonaplysilla violacea, collected from New Zealand coastal waters, contains as major constituents the diterpenoids aplyviolene (1a), norrisolide (2), dendrillolide A (3) aplyroseol-7 (4), spongian-16-one (5), chelonaplysin C (6), and a series of new compounds cheloviolene A-F and cheloviolin. Structures were assigned to cheloviolene A (7), [3aR-[3aα,4α(1R*,3aR*,8aS*),5β,6aα]]-5-hydroxy-4(1,4,4-trimethyl-8-methylenedecahydroazulen-1-yl) tetrahydrofuro [2,3- b] furan-2(3H)-one, cheloviolene B (8), [3aR-[3aα,4a(1R*,3aR*, 8aS*),5α,6aα]]-5-hydroxy-4-(1,4,4-trimethyl-8-methylenedecahydroazulen-1-yl) tetrahydrofuro [2,3-b]furan-2(3H)-one, cheloviolene C (9), [1'ξ(1R*,3aS*,7aS*),4ξ]-4-[1′-( acetyloxymethyl )-2′-(4,4,7a-trimethyloctahydro-1H-inden-1-yl)prop-2′-enyl] dihydrofuran -2(3H)-one, cheloviolene D (10), methyl [3α,4α(1R*,3aR*,8aS*)]-5-oxo-4-(1,4,4-trimethyl-8-methylenedecahydroazulen-1-yl)tetrahydrofuran-3-acetate, cheloviolene E (11), methyl [3α,4α-(1R*,3aS*,7aS*)]-5-oxo-4-[1′-(4,4,7a-trimethyloctahydro-1H-inden-1-yl) ethenyl ]tetrahydrofuran-3-acetate, and cheloviolene F (12), [4ξ,5ξ(1R*,3R*,8aS*)]-4-( acetyloxymethyl )-5-(1,4,4-trimethyl-8-methylenedecahydroazulen-1-yl) tetrahydro-2H-pyran-2-one, by using spectroscopic methods; the structure (13) was deduced for cheloviolin, [1S-[1α,5α,6α,8R*(1aS*,3aS*,7aS*,7b-R*)]]-6-acetyloxy-8-(4,4,7a-trimethyldecahydrocylopropa[a] naphthalen-la-yl )-2,7-dioxabicyclo- [3.2.1]octan-3-one.

Two syntheses of 6-methoxy-5-methylbenzo[h]pyrrolo[4,3,2-de]quinolin-4(5H)-one (eupolauramine) starting from 4-methoxynaphthylamine are described. One synthesis is highly efficient.

Extraction of the sponge Aplysilla sulphurea (Order, Dendroceratida) yielded two crystalline substances, aplysulphurin, C22H28O5, and aplysulphuride, C22H32O5 Chemical and spectroscopic evidence suggested that aplysulphurin, the title compound, had the structure (2). This was confirmed by a single-crystal X-ray determination.

A total synthesis of ageladine A has been achieved by exploiting a Pictet−Spengler-type condensation between 2-aminohistamine and 4,5-dibromo-2-formylpyrrole as the key step.

NMR studies show that the ternary octahedral Δ-cis-α- [Ru(RR-picchxnMe₂)(phen)]2+ cation binds with AT selectivity in the minor groove of [d(CGCGATCGCG)₂] and [d(ATATCGATAT)₂] duplexes through a non-intercalative interaction.

NMR studies show that the ternary octahedral Δ-cis-α- [Ru(RR-picchxnMe2)(phen)]2+ cation binds with AT selectivity in the minor groove of [d(CGCGATCGCG)2] and [d(ATATCGATAT)2] duplexes through a non-intercalative interaction.

The medicinal plant Bulbine capitatais used by the Basotho of southern Africa as a mild purgative and to cure gonorrhea infections. Organic extracts of the powdered root were found to be rich in anthraquinones, which may be responsible for the reported laxative effects. Examination of B. capitata led to the isolation of five known anthraquinones: chrysophanol, knipholone, isoknipholone, 10,7´-bichrysophanol and chrysalodin, and one new anthraquinone glycoside, M-4´-demethylknipholone-2´-O-‘-D-glucopyranoside.