Isolation and structure elucidation of ovalicin

The structure of ovalicin, a metabolite of the fungus Pseudeurotium ovalis with immunosuppressive activity, has been determined to be 11 .     

Isolation and structure elucidation of 11-desacetoxywortmannin

The structure of 11-desacetoxy-wortmannin ( 3 ), a new antiinflammatory metabolite of the fungus Penicillium funiculosum THOM, has been elucidated by physico-chemical methods and chemical correlation with wortmannin ( 1 ).     

Isolation and structure elucidation of ishwarol B

Ishwarol B was isolated from the bark oil of Cedrelopsis grevei and its structure elucidated by 1D and 2D NMR spectroscopy.     

Isolation and elucidation of the structure of homocryptolepinone

The structure of a new indolobenzazepine alkaloid, homocryptolepinone, isolated from extracts of the roots of the indigenous Ghanaian medicinal plant Cryptolepis sanguinolenta, is reported. The structure was determined using mass spectrometric, one-dimensional nOe difference nmr, and inverse-detected two-dimensional nmr experiments which included HMQC, IDR-(Inverted Direct Response)-HMQC-TOCSY, and HMBC experiments. The structure of homocryptolepinone is significant in that it may provide insight into the biogenesis of the benzpyrrolizinobenzazepine portion of the structure of the complex spiro nona-cyclic alkaloid cryptospirolepine previously isolated in these laboratories from C. sanguinolenta, and which has no precedent in alkaloid chemistry.     

Isolation and structure elucidation of genuine oat phytoalexin,avenalumin I

The major phytoalexin from oat leaves has been identified as 2-[2-(4-hydroxyphenyDethenyl] -6-hydroxy-4H-3,1-benzoxazin-4-one ($\text{A}$).     

2,4,5-三氧-1,3,2,4-二氮二磷杂环戊烷衍生物的合成和结构

本文报道了七个新的2,4,5-三氧-1,3,2,4-二氮二磷杂环戊烷衍生物的制备, 产物的结构经IR, ^1H和^31P NMR, MS以及元素分析证实, 并利用^31P NMR和GC-MS区分了化合物的顺式和反式异构体。     

Total synthesis of lyngbyatoxin A (teleocidin A-1) and teleocidin A-2

An eleven-step synthesis of tumor promoters, lyngbyatoxin A (=teleocidin A-1) (1) and teleocidin A-2 (2) was achieved from 1-tosylpyrrole (4) using a novel reaction forming 7-alkyl-4-aminoindoles (11).     

Isolation, structure elucidation, and biological activity of a new alkaloid from Zanthoxylum rhetsa

Several biologically active alkaloids (1-4, 6), including a new quinazoline-6-carboxylic acid (1), were isolated from the medicinal plant Zanthoxylum rhetsa, an evergreen tree, native to subtropical areas. Whereas the pharmacological properties of the plant extract and single constituents have been widely tested, we now show that all of the metabolites have antialgal activities, all but 6 are antibacterial, and 6 and the reduction product 5 (derived from 4) are also antifungal.     

Isolation and structure elucidation of gymnemic acids, antisweet principles of Gymnema sylvestre.

The structure of gymnemagenin (3 beta,16 beta,21 beta,22 alpha,23,28-hexahydroxy-olean-12-ene), the sapogenin of the antisweet principles of Gymnema sylvestre, was established by X-ray analysis of the 3 beta,23;21 beta,22 alpha-di-O-isopropylidene derivative. On the basis of this result, the structure of deacylgymnemic acid was elucidated as the 3-O-beta-glucuronide from the carbon-13 nuclear magnetic resonance spectra. Five antisweet principles, gymnemic acid-III, -IV, -V, -VIII, and -IX, were isolated in pure states from the hot water extract of leaves of Gymnema sylvestre. Of these, three (GA-III, -IV, and -V) were known, while two (GA-VIII and -IX) were new compounds. The structures of GA-VIII and -IX were elucidated as 3'-O-beta-D-arabino-2-hexulopyranosyl gymnemic acid-III and -IV, respectively.     

Isolation and structure elucidation of parnafungins, antifungal natural products that inhibit mRNA polyadenylation

The Candida albicans Fitness Test, a whole-cell screening platform, was used to profile crude fermentation extracts for novel antifungal natural products with interesting mechanisms of action. An extract with intrinsic antifungal activity from the fungus Fusarium larvarum displayed a Fitness Test profile that strongly implicated mRNA processing as the molecular target responsible for inhibition of fungal growth. Isolation of the active components from this sample identified a novel class of isoxazolidinone-containing natural products, which we have named parnafungins. These natural products were isolated as an interconverting mixture of four structural- and stereoisomers. The isomerization of the parnafungins was due to a retro-Michael ring-opening and subsequent reformation of a xanthone ring system. This interconversion was blocked by methylation of an enol moiety. Structure elucidation of purified parnafungin derivatives was accomplished by X-ray crystallography and NMR analysis. The biochemical target of these natural products has been identified as the fungal polyadenosine polymerase. Parnafungins demonstrated broad spectrum antifungal activity with no observed activity against gram-positive or gram-negative bacteria. The intact isoxazolidinone ring was required for antifungal activity. In addition, the natural products were efficacious in a mouse model of disseminated candidiasis.     

Synthesis and structure elucidation of N-methyl-4-(2-benzo-γ-pyronyl)-1,2,3-triazoles

When diazomethane was reacted with 2-cyano chromones, three isomeric N-methyltriazoles were obtained. They were isolated by liquid chromatography with three different solvents for elution. Complete elucidation of the structures was performed both by pmr and cmr spectrography; X-ray analysis is in agreement with the proposed structures.     

Isolation and structure elucidation of ovatoxin-a, the major toxin produced by Ostreopsis ovata

Since 2005, the benthic dinoflagellate Ostreopsis cf. ovata has bloomed across the Mediterranean basin, provoking serious toxic outbreaks. LC/MS studies have identified a number of palytoxin-like compounds, termed ovatoxins, along with trace amounts of putative palytoxin as the causative agents of the O. cf. ovata -related human sufferings. So far, any risk assessment for ovatoxins as well as establishment of their allowance levels in seafood has been prevented by the lack of pure toxins. The present paper reports on the isolation, NMR-based structural determination, and preliminary mouse lethality evaluation of ovatoxin-a, the major toxic compound contained in O. cf. ovata extracts. Availability of pure ovatoxin-a will open the double prospect of fully evaluating its toxicity and preparing reference standards to be employed in LC/MS quantitative analyses. Elucidation of ovatoxin-a's complex structure will ultimately herald the understanding of the molecular bases of ovatoxins bioactivity.     

Synthesis and the molecular and crystal structure of 1, 4-dihydro-1-methyl-4-(2, 3, 3-tricyanoallylidene)quinoline

The reaction of 1, 4-dimethylquinolinium iodide with tetracyanoethylene in presence of triethylamine proceeds highly regioselectively with the formation of l, 4-dihydro-l-methyl-4-(2, 3, 3-tricyanoallylidene)quinoline. It was shown by an x-ray structural investigation that its crystal is built from two, not quite planar, symmetrically independent molecules (IIIa) and (IIIb): The dihedral angles in these between the dihydroquinoline nucleus and the tricyanoallylidene group are 8.6 and 10.8. An examination is made of the influence on the structure of the molecules of steric factors and effects of the conjugation of the donor and acceptor parts of the molecules, leading to considerable intramolecular transfer of charge. In the crystal the molecules form stacks of the type ...aabb... with the participation of both symmetrically independent molecules and with interplanar distances d of 3.341, 3.449, and 3.347 å, which may be conducive to intermolecular transfer of charge.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 690–696, March, 1991.     

两色乌头生物碱的分离和结构测定

从吉林省抚松县采集的两色乌头(Acomitum albouiolaceum Kom.)的根,分得九种C~10二萜生物碱,其中四种为新化合物:两色乌碱甲(alboviolaconitine A)(1),两色乌碱乙(alboviolaconitine B)(2),两色乌碱丙(alboviolaconitine C)(3)和两色乌碱丁(alboviolaconitine D)(4).其余五种成分鉴定为瑟佩定(septentriodine)(5),牛扁亭(lycaconitine)(6),东乌头定(avadharidine)(7),帕巴乌碱铵(ammoniumpuberaconitine)(8)和牛扁碱 (lycotonine)(9).经分析各种光谱数据及化学方法转为已知物,确定了1-4的结构.     

Isolation and structure elucidation of Chlorofusin, a novel p53-MDM2 antagonist from a Fusarium sp.

Wild-type p53 plays a crucial role in the prevention of cancer. Since dysfunction of p53 can be caused by increased levels of the protein MDM2, small molecules which antagonize the interaction between these two proteins have potential in cancer therapy. The discovery and structure determination of a fungal metabolite, chlorofusin, which antagonizes the p53/MDM2 interaction are reported.