Total synthesis, structure revision, and absolute configuration of (+)-yatakemycin

The total synthesis of the reported structure 2 for yatakemycin, an exceptionally potent, naturally occurring antitumor agent disclosed in 2003, and its lack of correlation with the natural product are detailed. On the basis of spectroscopic distinctions between 2 and yatakemycin, the natural product structure was reformulated as 3, now bearing a thiomethyl ester versus thioacetate in the left-hand subunit. Total synthesis of 3 provided a compound nearly identical to but still subtly distinct from the natural product. A second reformulation of the yatakemycin structure as 1, incorporating the alternatively substituted right-hand subunit as well as the initial thiomethyl ester reformulation, was confirmed by total synthesis of both (+)- and ent-(-)-1 in studies that also unambiguously established the absolute configuration of the natural product.     

Calophyline A, a new rearranged monoterpenoid indole alkaloid from Winchia calophylla

Calophyline A (1), a novel unprecedented rearranged monoterpenoid indole alkaloid, along with a new natural product N-methyl aspidodasycarpine (2) and six known analogues, was isolated from the trunk barks of Winchia calophylla. The structure of compound 1 was elucidated on the basis of spectroscopic data and then confirmed by a single-crystal X-ray crystallographic analysis. A hypothetical biogenetic pathway for compound 1 was proposed. All isolated compounds were evaluated for their in vitro cytotoxicity against a small panel of human cancer cell lines.     

Chemical constituents of Caryopteris tangutica

A new compound (1), along with 18 known compounds, was isolated from Caryopteris tangutica. On the basis of spectroscopic methods, with special emphasis on 1D- and 2D-NMR techniques, the structure of the new compound was characterised as 6-hydroxy-6-methylcyclohex-2-en-1-one (1).     

Structure elucidation and complete NMR spectral assignments of a novel sesquiterpene glycoside from Ixeris sonchifolia

A novel sesquiterpene glycoside was isolated from the whole plant of Ixeris sonchifolia. The structure was established as 1(10)E-4Z-3alpha-hydroxy-germacra-1(10),4,11(13)-trien-6, 12-olide-14-O-beta-D-glucopyranoside (1) on the basis of spectroscopic techniques and chemical analysis.     

WYE‐120318, a ring contraction product of methylnaltrexone,and structure revision of coniothyrione

A contracted ring degradation product, WYE‐120318 (compound 2), was discovered during the development phase for methylnaltrexone bromide (compound 1) drug substance. The compound was isolated by high‐performance liquid chromatography fractionation, and its structure was determined by spectroscopic data analyses. WYE‐120318 is formed from methylnaltrexone through a benzyl‐benzilic acid type rearrangement reaction to yield an α‐hydroxy‐cyclopentanecarboxylic acid substructure. The proposed structure and the formation mechanism are confirmed by the synthesis of WYE‐120318 from methylnaltrexone (compound 1). A similar benzyl‐benzilic acid type rearrangement reaction can be envisioned as the biological origin of remisporine A (compound 3), a naturally occurring cyclopentadienyl compound that autocatalytically dimerizes to remisporine B (compound 4). The structure of remisporine A was deduced from its dimer 4. Coniothyione (compound 5) can be considered as the first example of a stable natural product bearing the remisporine A skeleton. However, the regiochemistry of the chlorosubstitution in the coniothyrione structure needs to be revised to compound 6 on the basis of the nuclear magnetic resonance data and biogenesis analysis. Copyright © 2012 John Wiley & Sons, Ltd.     

New clerodane diterpenoid from the bulbils of Dioscorea bulbifera

A new clerodane diterpenoid has been isolated from the acetone extract of bulbils of Dioscorea bulbifera. The structure of compound 1 was established as 15,16-epoxy-6alpha-O-acety1-8beta-hydroxy- 9-nor-clero-13(16),14-diene-17,12;18,2-diolide on the basis of comprehensive spectroscopic techniques.     

Chemical studies on the constituents of the chinese medicinal herb Euphorbia helioscopia L

Euphoheliosnoid D (1), a new jatrophone-type diterpenoid, was isolated together with 22 known metabolites from the Chinese medicinal herb Euphorbia helioscopia L. The structure and relative stereochemistry of 1 was elucidated on the basis of spectroscopic methods. Compounds 14-23 were obtained from the species for the first time while compound 14, 2alpha-hydroxy helioscopinolide B, was isolated as a new natural product.     

Xanthine oxidase inhibitors from the heartwood of Vietnamese Caesalpinia sappan

From the MeOH extract of Vietnamese Caesalpinia sappan, a novel biogenetically exclusive benzindenopyran, with a new carbon framework, neoprotosappanin (1), and a new compound, protosappanin A dimethyl acetal (3), were isolated together with protosappanin E-2 (2), neosappanone A (4), and 13 previously reported phenolic compounds (5-17). Their structures were elucidated on the basis of spectroscopic data. Compounds 1-4, 7, 13, and 15-17 showed significant xanthine oxidase inhibitory activity in a concentration-dependent manner, and sappanchalcone (17) showed the most potent activity with an IC50 value of 3.9 microM, comparable to that of positive control allopurinol (IC50, 2.5 microM). The kinetic study of these inhibitors indicated that they are competitive inhibitors, the same as allopurinol, except for 1 and 16 which are noncompetitive inhibitors.     

Lecythomycin, a new macrolactone glycoside from the endophytic fungus Lecythophora sp

A new macrolactone glycoside, lecythomycin (1), 23-methyl-3-(1-O-mannosyl)-oxacyclotetracosan-1-one, was isolated from the endophytic fungus Lecythophora sp. (code 30.1), an endopyte of the Indonesian plant Alyxia reinwardtii. The structure of 1 was elucidated on the basis of NMR spectroscopic and mass spectrometric data. The isolated compound displayed antifungal activity against strains of Aspergillus fumigatus and Candida kruzei at minimal inhibitory concentrations (MIC) of 62.5-125 microg/mL.     

Neoengleromycin,a Novel Compound from Engleromyces goetzii

A novel N‐containing compound, neoengleromycin ( 1 ) was isolated from the fruiting bodies of the ascomycete Engleromyces goetzii together with two known cytochalasins: cytochalasin D ( 2 ) and 19,20‐epoxycytochalasin D ( 3 ). Structures were established by spectroscopic (including 2D‐NMR) and chemical means. Neoengleromycin ( 1 ) possesses the rare structure of an N‐substituted hydroxamic acid and represents a new type of natural products.     

Ent-untenospongin A, a New C21 Furanoterpene from the Indian Marine Sponge Hippospongia sp

Many marine sponges of the family Spongiidae, in particular, the genus HiPPospongiafrequently afford terpenoids containing ZI carbons and displaying two Asubstitutedfuran moieties at the end of the molecule2. These unusual compounds are probablyderived from higher terpenoids from a biogenetic point of view. During our studies onbioactive substances from marine organisms, we investigated the extracts of the indiansponge HiPPospongia sp. and isolated a new C,, furanoterpene, named enluntenos…     

大萼香茶菜中的新二萜化合物

报道从大萼香茶菜叶的乙醇提取物中分离得到一种新的二萜类化合物, 并命名为大萼香茶菜癸素(1). 其药理活性实验结果证明, 该化合物对体外培养的Hela细胞有较强的抑制作用.     

Acremolin,a new 1H-azirine metabolite from the marine-derived fungus Acremonium strictum

Acremolin (1), a novel modified base, was isolated from the culture broth of the marine fungus Acremonium strictum. Based on combined spectroscopic analyses, the structure of this compound was that of a methyl guanine base containing an isoprene unit. In addition, the presence of a 1H-azirine moiety is unprecedented among natural products. This compound exhibited weak cytotoxicity against an A549 cell line.     

Benhamycin, novel alkaloid from terrestrial Streptomyces sp

During our screening for bioactive natural compounds from microorganisms, a novel alkaloid has been isolated from a terrestrial Streptomyces sp. isolate NR12, and named as benhamycin (1). This was along with the known metabolites, uracil, thymine, p-hydroxybenzoic acid, 2'-deoxyuridin, tryptophol, indolyl-3-carboxylic acid, and indolyl-3-carbaldehyde. Chemical structure of the novel compound was determined by detailed analysis of its spectroscopic data (extensive NMR experiments, 1 & 2D, MS spectroscopy, and MS high resolution). Structurally, Benhamycin (1) is a pentacyclic aromatic compound bearing an acridine moiety lactamized with benzene. Biological studies showed that the strain extract was moderately active against Gram-positive, Gram-negative bacteria and fungi.     

Revised structure of kasarin, an antibacterial pyrazinone compound from the marine microorganism Hyphomycetes sp.

Kasarin is an antibacterial marine alkaloid that was isolated from the microorganism Hyphomycetes sp. Its structure was previously reported to be an azetinone compound 1. However, detailed spectroscopic analysis of the natural compound and its related synthetic analogs revealed that the structure of kasarin should be revised to be a novel 5-malonyloxy-1-methoxy-pyrazin-2(1H)-one derivative 2.     

Acerolide, a new cytotoxic cembranolide from the soft coral Pseudopterogorgia acerosa

A new cembranolide, acerolide (1) together with the known compound pseudopterolide (2) were isolated from the 2-propanol extract of the soft coral Pseudopterogorgia acerosa. The structure of 1 was determined on the basis of detailed spectroscopic analysis. Compound 1 showed moderate in vitro cytotoxicity against a panel of 14 tumor cell lines.     

Avenic acid,a new amino acid possessing an iron chelating activity

A new amino acid derivative possessing an iron chelating activity was isolated from root washings of water cultured $\text{Avena sativa}$ under iron deficient conditions. The structure of this compound, avenic acid A has been determined as 2(S),3′(S),3″(S)-N-[3-(3-hydroxy-3-carboxypropylamino)-3-carboxypropyl]-homoserine (1) on the basis of chemical and spectroscopic evidence.     

Stolonilactone, a novel terpenoid-related compound, isolated from the Okinawan soft coral Clavularia koellikeri

A novel terpenoid-related compound, stolonilactone (1), was isolated from the Okinawan soft coral Clavularia koellikeri. The structure of 1 was elucidated on the basis of spectroscopic analysis. A possible biogenesis of 1 through the [4 + 2]-cycloaddition of a trisnorsesquiterpenoid-type diene and a cembranolide-type dienophile is proposed.     

Iridoid,phenylethanoid and flavonoid glycosides from Forsythia suspensa

Abstract

As part of our continuing efforts to explore bioactive compounds from natural resources, a new iridoid glycoside, adoxosidic acid-6′-oleuroperic ester (1), together with one known phenylethanoid glycoside (2) and two known flavonoid glycosides (3–4) were isolated from the fruit of Forsythia suspensa. The structure of the new compound (1) was elucidated through 1D and 2D NMR spectroscopic data and HR-ESIMS. Interestingly, compound 1 was a monoterpene ester of one iridoid glycoside. Compounds 2–4 were identified as calceolarioside A (2), kaempferol-3-O-rutinoside (3), kampferol-3-O-robinobioside (4) on the basis of NMR spectroscopic data analyses and comparison with the data reported in the literature. The antiviral activity aganisist influenza A (H5N1) virus of compound 1 was studied as well.     

A novel sesquiterpene alcohol from Fimetariella rabenhorstii, an endophytic fungus of Aquilaria sinensis

A novel sesquiterpene alcohol, named frabenol (1), was isolated from liquid cultures of Fimetariella rabenhorstii A20, an endophytic fungus of the agarwood-forming plant Aquilaria sinensis (Lour.) Gilg. The structure of the new compound was elucidated on the basis of spectroscopic methods. The finding of a sesquiterpenoid compound in F. rabenhorstii A20 implied that endophytic fungi of agarwood-producing plants could also contribute to the generation of fragrant chemicals during the agarwood formation processes.