Characterization of inthomycin biosynthetic gene cluster revealing new insights into carboxamide formation.

Inthomycins are polyketide antibiotics which contain a terminal carboxamide group and a triene chain. Inthomycin B (1) and its two new analogues 2 and 3 were isolated from the crude extract of Streptomyces pactum L8. Identification of the gene cluster for inthomycin biosynthesis as well as the 15N-labeled glycine incorporation into inthomycins are described. Combined with the gene deletion of the rare P450 domain in the NRPS module, a formation mechanism of carboxamide moiety in inthomycins was proposed via an oxidative release of the assembly chain assisted by the P450 domain.

Cangumycins A-F, six new angucyclinone analogues with immunosuppressive activity from Streptomyces.

Cangumycins A-F (1-6), six new angucyclinone analogues, together with two known ones (7 and 8), were isolated from the fermentation broth of a soil-derived Streptomyces sp. KIB-M10. Structures of these compounds were elucidated via a joint use of spectroscopic analyses and single-crystal X-ray diffractions. Among them, cangumycins E (5) and F (6) share a C-ring cleaved backbone, and cangumycins B (2) and E (5) exhibit potent immunosuppressive activity (IC50 8.1 and 2.7 µmol·L-1, respectively) against human T cell proliferation at a non-cytotoxic concentration.

A new actinomycin Z analogue with an additional oxygen bridge between chromophore and ß-depsipentapeptide from Streptomyces sp. KIB-H714.

Actinomycin Z6 (1), a new member of the actinomycin family, along with three congeners of the Z-type (Z1, Z3, Z5) actinomycins, are produced from Streptomyces sp. KIB-H714. Their structures were authenticated by comprehensive spectroscopic data interpretation. Different from all the reported Z-type actinomycins, the ß-ring of the new compound actinomycin Z6 includes an additional ring linked between the actinoyl chromophore and ß-peptidolactone. In Z3 and Z5, the L-threonine in ß-depsipeptide is replaced by the unusual 4-chlorothreonine, an amino acid rarely found in actinomycin family. All isolates were evaluated for cytotoxicity against five human tumor cell lines and for inhibitory activity against Candida albicans and Staphylococcus aureus.

Glycosylated piericidins from an endophytic streptomyces with cytotoxicity and antimicrobial activity.

Two new glycosylated piericidins, glucopiericidinol A3 (1) and 7-demethyl-glucopiericidin A (2), along with four known analogs were isolated from the culture broth of Streptomyces sp. KIB-H1083. The chemical structures of new compounds were elucidated by spectroscopic analyses. Their cytotoxicity on HL-60, SMMC-772, A-549, MCF-7, and SW480 cell lines, as well as antimicrobial activities was evaluated. The results showed that glucopiericidin A (4) has potent cytotoxicity against HL-60, SMMC-772, A-549, and MCF-7 cell lines with IC50 values of 0.34, 0.65, 0.60, and 0.50 µM, respectively. For the antimicrobial activity, piericidin A (6) showed most powerful inhibitory activities against Xanthomonas oryzae pv. oryzicola, and Penicillium decumbens.

Non-enzymatic pyridine ring formation in the biosynthesis of the rubrolone tropolone alkaloids.

The pyridine ring is a potent pharmacophore in alkaloid natural products. Nonetheless, its biosynthetic pathways are poorly understood. Rubrolones A and B are tropolone alkaloid natural products possessing a unique tetra-substituted pyridine moiety. Here, we report the gene cluster and propose a biosynthetic pathway for rubrolones, identifying a key intermediate that accumulates upon inactivation of sugar biosynthetic genes. Critically, this intermediate was converted to the aglycones of rubrolones by non-enzymatic condensation and cyclization with either ammonia or anthranilic acid to generate the respective pyridine rings. We propose that this non-enzymatic reaction occurs via hydrolysis of the key intermediate, which possesses a 1,5-dione moiety as an amine acceptor capable of cyclization. This study suggests that 1,5-dione moieties may represent a general strategy for pyridine ring biosynthesis, and more broadly highlights the utility of non-enzymatic diversification for exploring and expanding natural product chemical space.

Tropolone Ring Construction in the Biosynthesis of Rubrolone B, a Cationic Tropolone Alkaloid from Endophytic Streptomyces.

Rubrolones are tropolonoid natural products with a unique carbon skeleton. Extensive secondary metabolite analysis of the endophytic Streptomyces sp. KIB-H033 revealed a new class of rubrolone analogue possessing a rare benzoic acid-pyridine inner salt moiety. Precursor feeding with [(13)C]-acetate revealed a labeling pattern consistent with tropolone moiety construction via type-II PKS chemistry followed by complex oxidative rearrangements. This bacterial biosynthetic route represents a surprising departure from fungal tropolone assembly during stipitatic acid biosynthesis.

New duclauxamide from Penicillium manginii YIM PH30375 and structure revision of the duclauxin family.

Duclauxamide A1 (1), a new polyketide-derived heptacyclic oligophenalenone dimer with a N-2-hydroxyethyl moiety, was isolated from Penicillium manginii YIM PH30375. Spectroscopic analysis, X-ray single crystal diffraction, and (13)C NMR DFT calculations confirmed that compound 1 and other duclauxin analogues possess the unified S configuration at C-9', which corrects a long-standing misrepresentation of duclauxins as C-9'R epimers. A plausible biosynthetic pathway for duclauxins is proposed on the basis of previous acetate labeling results for duclauxin and sclerodin.

2-Chloro-N-methyl-N-[2-(methyl-amino)-phen-yl]acetamide.

The title compound, C(10)H(13)ClN(2)O, was obtained as a by-product in the reaction of 2-chloro-methyl-1H-benzimidazole, dimethyl sulfate and toluene to synthesise 2-chloro-methyl-1-methyl-benzimidazole. The dihedral angle between the benzene ring and the acetamide group is 89.72  (6)° while that between the aromatic ring and the chloracetyl group is 84.40 (4)°. In the crystal, adjacent mol-ecules are linked by pairs of N-H⋯O hydrogen bonds into inversion dimers.

Natural products as sources of new fungicides (I): synthesis and antifungal activity of acetophenone derivatives against phytopathogenic fungi.

Several series of 45 acetophenone derivatives bearing various alkyl or benzyl substituents were conveniently synthesized and their structures characterized by (1)H and (13)C NMR spectroscopy, HRMS and single-crystal X-ray analysis. Their in vitro antifungal activities against a panel of phytopathogenic fungi were evaluated by mycelial growth rate assay. Of them, 12 derivatives (e.g., 3a-c, 4c and 4e) exhibited more potent antifungal effects on some phytopathogens than a commercial fungicide hymexazol as positive control. In particular, compound 3b with IC50 values of 10-19 µg/mL was found to be the most active in this series and might be a potential lead structure for further optimization. The preliminary structure-activity relationship (SAR) studies of a series of acetophenones are also discussed.

1-(4-Benz-yloxy-2-hy-droxy-phen-yl)ethanone.

The title compound, C(15)H(14)O(3), has been obtained from the reaction of 2,4-dihy-droxy-acetophenone, potassium carbonate and benzyl bromide. The remaining hy-droxy group is involved in an intra-molecular O-H⋯O hydrogen bond. In the crystal, inter-molecular C-H⋯O contacts occur.

4-Allyl-2-meth-oxy-phenyl 3,4-dichloro-benzene-sulfonate.

The title compound, C(16)H(14)Cl(2)O(4)S, was obtained by the reaction of eugenol (4-allyl-2-meth-oxy-phenol) and 3,4-dichloro-benzene-sulfonyl chloride. The dihedral angle between the benzene rings in the mol-ecule is 40.53 (4)°. No significantly short inter-molecular contacts are observed in the crystal structure.

Structure and absolute configuration of toxic polyketide pigments from the fruiting bodies of the fungus Cortinarius rufo-olivaceus.

Two new polyketide-derived pigments, named rufoolivacins B (), and D (), with a 4',10-coupled aryl linkage between polysubstituted 1-naphthol and 1,4- or 1,2-anthraquinone, together with nine known metabolites including rufoolivacins A () and C (), have been isolated from the fruiting bodies of the Chinese toadstool Cortinarius rufo-olivaceus (basidiomycetes). Their structures were characterized on the basis of spectroscopic methods, including 2D-NMR experiments (COSY, NOESY, HSQC, and HMBC). The axial chirality of and was assigned through analysis of their CD spectra and ZINDO and TDDFT calculations. Compounds and were found to be unusual natural products incorporating an ortho-anthraquinone chromophore. All the metabolites were shown to be toxic toward the brine shrimp.

Pecipamide, a new sphingosine derivative from the cultures of Polyporus picipes (Basidiomycetes).

A new C(18)-ceramide congener named pecipamide (1), together with the known ergosta-4,6,8(14),22-tetraen-3-one (2), was isolated from the solid fermentations of the basidiomycetous fungus Polyporus picipes. The structure of the new metabolite was established as (2'R,2S,3R)-N-2'-hydroxyheptadecanoyl-2-amino-octadecane-1,3-diol on the basis of spectroscopic data, including 1D- and 2D- nuclear magnetic resonance spectroscopy (NMR) experiments, as well as by means of mass spectrometric measurements (MS).

1-[2-(3,5-Difluoro-benz-yloxy)phen-yl]ethanone.

In the title compound, C(15)H(12)F(2)O(2), the dihedral angle between the aromatic rings is 70.43 (4)°. The crystal packing exhibits no significantly short inter-molecular contacts.

1-[4-(3,5-Difluoro-benz-yloxy)-2-hy-droxy-phen-yl]ethanone.

The title compound, C(15)H(12)F(2)O(3), has been obtained by the reaction of 2,4-dihy-droxy-lacetonephenone, potassium carbonate and 3,5-difluoro-benzyl bromide. The hy-droxy group is involved in an intra-molecular O-H⋯O hydrogen bond in each of the two independent mol-ecules in the asymmetric unit. The dihedral angle between the aromatic rings is 0.5 (2)° in one molecule and 1.9 (2)° in the other. In the crystal, weak C-H⋯O inter-actions link the mol-ecules into tetra-meric units aligned perpendicular to b.

2,4-Dichloro-6-[2-meth-oxy-4-(prop-2-en-1-yl)phen-oxy]-1,3,5-triazine.

The title compound, C(13)H(11)Cl(2)N(3)O(2), was obtained by the reaction of eugenol and cyanuric chloride. The dihedral angle between the benzene and triazine rings is 87.56 (4)°. Two C atoms of the allyl group are disordered over two sites in a 0.72 (2):0.28 (2) ratio.

Cytotoxic metabolites produced by Alternaria no.28, an endophytic fungus isolated from Ginkgo biloba.

From the medicinal plant Ginkgo biloba the fungal endophyte Alternaria no.28 was isolated. Extract of the fungus grown in liquid culture media exhibited marked cytotoxic activity when tested in vitro against brine shrimp (Artemia salina). Eight compounds were isolated from the extract of cultures of this endophytic fungus and were elucidated as alterperylenol (1), altertoxin I (2), alternariol (3), alternariol monomethyl ether (4), tenuazonic acid (5) and its derivative (6), together with ergosterol and ergosta-4, 6, 8, 22-tetraen-3-one by means of spectroscopic analysis. Among them, both 5 and 6 showed significant cytotoxic effects in the brine shrimp bioassy, with mortality rates of 73.6% and 68.9%, respectively, at a concentration of 10 microg x mL(-1), and they were first isolated from endophytic fungi.

Antifungal activity of alkaloids from the seeds of Chimonanthus praecox.

Two alkaloids, D-calycanthine (1) and L-folicanthine (2), were isolated from the active MeOH extract of the seeds of Chimonanthus praecox LINK. The structures of the two compounds were established by (1)H- and (13)C-NMR, and MS (FAB, ESI) analyses. In the in vitro tests, compounds 1 and 2 showed significant inhibitory activities against five plant pathogenic fungi Exserohilum turcicum, Bipolaris maydis, Alternaria solani, Sclerotinia sderotiorum, and Fusarium oxysportium, among which B. maydis was found to be the most susceptible to 1 with an EC(50) value of 29.3 microg/ml, followed by S. sderotiorum to 2 with an EC(50) value of 61.2 microg/ml. To our knowledge, this is the first report of isolation and LC/MS/MS identification as well as of antifungal properties of these alkaloids from the seeds of this plant.

Polyhydroxylated steroids from an endophytic fungus, Chaetomium globosum ZY-22 isolated from Ginkgo biloba.

A novel polyhydroxylated C(29)-sterol, 25xi-methyl-22-homo-5alpha-cholest-7,22-diene-3beta,6beta,9alpha-triol, designated globosterol (1), together with one known tetrahydroxylated ergosterol (22E, 24R)-ergosta-7,22-diene-3beta,5alpha,6beta,9alpha-tetraol (2) has been isolated from the cultures of an endophytic fungus, Chaetomium globosum ZY-22 originated from the plant Ginkgo biloba. The structures and relative configurations of 1 and 2 were established on the basis of extensive spectroscopic analyses including 1D and 2D NMR ((1)H-(1)H COSY, HSQC, HMBC, and NOESY) experiments and comparison with the literature. Globosterol (1) possesses an unprecedented 25-methyl Delta(22)-C(10)-side chain and Delta(7)-3beta,6beta,9alpha-hydroxy-steroid nucleus, which represents the first example for C(29)-steroids of the group.

1-[4-(3-Chloro-prop-oxy)-2-hydroxy-phen-yl]ethanone.

The title compound, C(11)H(13)ClO(3), has been obtained in the reaction of 2, 4-dihydroxy-lacetonephenone, potassium carbonate and 1-bromo-3-chloro-hexane. The hydr-oxy group is involved in an intra-molecular O-H⋯O hydrogen bond. The crystal packing exhibits no significantly short inter-molecular contacts.