Synthesis of Obyanamide, a Marine Cytotoxic Cyclic Depsipeptide

Obyanamide 1 is a cyclic depsipeptide that was recently isolated from the marine cyanobacterium Lyngbya confervoides by Moore and co-workers1. This compound displayed a potent inhibitory effect on both KB and LoVo cells in vitro. Several structural analog…     

Toward the Total Synthesis of Onchidin,a Cytotoxic Cyclic Depsipeptide from a Mollusc

The total synthesis of onchidin ( 1 ), a cytotoxic, C₂‐symmetric cyclic decadepsipeptide from a marine mollusc, according to the published structure, is described. A novel β‐amino acid, (2S,3S)‐3‐amino‐2‐methyl‐7‐octynoic acid (AMO), was efficiently prepared in high yield with high diastereo‐ and enantioselectivity based on a catalytic asymmetric three‐component Mannich‐type reaction with a chiral zirconium catalyst. The formation of sterically unfavorable N‐methyl amide and hindered ester bonds were successfully demonstrated, and final macrocyclization was achieved at a secondary‐amide site. Completion of the synthesis of 1 suggested that a revision of the structure of the natural product is required. Two diastereomers were also synthesized as candidates for the actual structure of onchidin. Furthermore, efficient solid‐phase methods were employed for the combinatorial synthesis of other derivatives to clarify the real structure of onchidin. The solid‐phase assembly of a pentadepsipeptide containing all the building blocks was established followed by dimeric cyclization in solution.     

天然海洋环酯肽Stereocalpin A中间体的合成

以D-苯丙氨酸为原料,经过硼氢化钠/碘还原后与三光气在碱性条件下环合得到Evans手性助剂(R)-4-苄基-2-噁唑烷酮(2),然后将其与丙酰氯缩合,经过LDA偶联、反式Aldol等反应,合成了天然环酯肽StereocalpinA中含有的独特结构片段,该片段对3种人实体瘤细胞系(HT-29,B16/F10,HepG2)具有中等细胞毒性,总收率为30.6%。结果表明,合成路线简便可行,反应产率高,立体选择性好。是制备该化合物的有效途径。     

New cytotoxic salinosporamides from the marine Actinomycete Salinispora tropica

An extensive study of the secondary metabolites produced by the obligate marine actinomycete Salinispora tropica (strain CNB-392), the producing microbe of the potent proteasome inhibitor salinosporamide A (1), has led to the isolation of seven related gamma-lactams. The most important of these compounds were salinosporamide B (3), which is the deschloro-analogue of 1, and salinosporamide C (4), which is a decarboxylated pyrrole analogue. New SAR data for all eight compounds, derived from extensive testing against the human colon carcinoma HCT-116 and the 60-cell-line panel at the NCI, indicate that the chloroethyl moiety plays a major role in the enhanced activity of 1.     

Aspochalasin H1: A New Cyclic Aspochalasin from Hawaiian Plant-Associated Endophytic Fungus Aspergillus sp. FT1307

Aspergillus is one of the most diverse genera, and it is chemically profound and known to produce many biologically active secondary metabolites. In the present study, a new aspochalasin H1 (1), together with nine known compounds (2–10), were isolated from a Hawaiian plant-associated endophytic fungus Aspergillus sp. FT1307. The structures were elucidated using nuclear magnetic resonance (NMR) (¹H, ¹H-¹H COSY, HSQC, HMBC, ROESY and 1D NOE), high-resolution electrospray ionization mass spectroscopy (HRESIMS), and comparisons with the reported literature. The absolute configuration of the new compound was established by electronic circular dichroism (ECD) in combination with NMR calculations. The new compound contains an epoxide moiety and an adjacent trans-diol, which has not been reported before in the aspochalasin family. The antibacterial screening of the isolated compounds was carried out against pathogenic bacteria (Staphylococcus aureus, Methicillin-resistant S. aureus and Bacillus subtilis). The antiproliferative activity of compounds 1–10 was evaluated against human breast cancer cell lines (MCF-7 and T46D) and ovarian cancer cell lines (A2780).     

Two New Antibacterial Anthraquinones from Cultures of an Endophytic Fungus Phomopsis sp.

Chemistry of Natural Compounds - Two new anthraquinones, 3-hydroxy-6-hydroxymethyl-2,5-dimethylanthraquinone (1) and 6-hydroxymethyl-3-methoxy-2,5-dimethylanthraquinone (2), were isolated from the...     

Two New Octahydronaphthalene Derivatives from Trichoderma spirale,an Endophytic Fungus Derived from Aquilaria sinensis

Two new octahydronaphthalene derivatives, trichodermic acid A ( 1 ) and trichodermic acid B ( 2 ), along with a known analog, trichodermic acid ( 3 ), and a known modified dipeptide, trichodermamide A ( 4 ), were isolated from the extract of Trichoderma spirale, an endophytic fungus present in the medicinal plant Aquilaria sinensis. The structures of these compounds were established by extensive analysis of their spectroscopic data including 1D‐ and 2D‐NMR and MS data.     

A New Degraded Sesquiterpene from Marine Actinomycete Streptomyces sp. 0616208

A new degraded sesquiterpene was isolated from the marine actinomycete Streptomyces sp. 0616208. Its structure was elucidated as (1α,4aα,5α, 7β, 8aβ)-5, 8a-dimethyl-decahydronaphthalene -1, 4a, 7-triol on the basis of spectroscopic data.     

New Cyclic Diarylheptanoids from Platycarya strobilacea

Five new cyclic diarylheptanoids (platycary A–E, compounds 1–5) and three previously identified analogues (i.e., phttyearynol (compound 6), myricatomentogenin (compound 7), and juglanin D (compound 8)) were isolated from the stem bark of Platycarya strobilacea. The structures of these compounds were determined using NMR, HRESIMS, and electronic circular dichroism (ECD) data. The cytotoxicity of compounds 1–5 and their ability to inhibit nitric oxide (NO) production, as well as protect against the corticosterone-induced apoptosis of Pheochromocytoma (PC12) cells, were evaluated in vitro using the appropriate bioassays. Compounds 1 and 2 significantly inhibited the corticosterone-induced apoptosis of PC12 cells at a concentration of 20 μΜ.     

Three New Triterpenes from Xylarialean sp. A45, an Endophytic Fungus from Annona squamosa L.

From the fermentation extract of Xylarialean sp. A45, an endophytic fungus of Annona squamosa L., three new triterpenes, namely xylariacins A–C ( 1 – 3 , resp.) were obtained. Their structures were determined by spectroscopic analyses, including 1D‐ and 2D‐NMR experiments and HR‐ESI‐Q‐TOF mass spectrometry. The in vitro cytotoxic activities of compounds 1 – 3 were tested against human tumor cell line HepG2, and these compounds showed modest cytotoxic activity.     

Two New Cyclic Peptides from Psammosilene tunicoides

PsammosilenetunicoidesW.C.WuetC.YWu,amonotypegenusplantbelongingtoCaryophyllaceae,isafamousmedicinalherbinYunnanprovince.Itisusedasanodyneandhaemastaticagent1.Studiesonitssaponinshavebeenreported2-4.Asapartofourinvestigationonthenewbioactivecyclopeptidesfromhigherplants'-",thechromatographicpurificationoftheacetone-solublefractionofthedriedrootsofthetitleplant(25Kg)ledtotheisolationoftwonewcyclicoctapeptides,psammosileninsA(10mg)andB(6mg).Thispaperdealswiththeelucidationoftheirstructures.…     

A New Cyclic Peptide from Schnabelia tetradonta

A new cyclic octapeptide (schnabepeptide B) was isolated from the aerial part of Schnabelia tetradonta (Sun) C. Y. Wu et C. Chert (Lamiaceae). Its structure was elucidated as cyclo-(NH-Trp-Gly1-Leu1-Gly2-Pro1-Pro2-Leu2-Pr03-CO) on the basis of extensive 2D NMR and MS spectra.     

Asperphenyltones A and B: New Phenylfuropyridinone Skeleton from an Endophytic Aspergillus sp. GXNU-A1

Chemical investigation of the fermentation extract of the mangrove endophytic fungus Aspergillus sp. GXNU-A1, isolated from Acanthus ilicifolius L., discovered an undescribed pair of enantiomers (asperphenyltones A and B (±1)), together with four previously described metabolites: nodulisporol (2), isosclerone (3), 2,3,4-trihydroxy-6-(hydroxymethyl)-5-methylbenzyl alcohol (4), and 4,6-dihydroxy-5-methoxy-7-methyl-1,3-dihydroisobenzofuran (5). Analyses of the 1D and 2D NMR spectroscopic data of the compounds supported their structural assignments. The presence of the asperphenyltones A and B, which are a pair of enantiomers, was established by HR-ESI-MS, 1D and 2D NMR data and confirmed by single-crystal X-ray diffraction analysis. Metabolites 1–5 were evaluated for their anti-inflammatory effects on the production of nitric oxide (NO), and 1, 3, and 4 showed significant potential inhibitory activities against NO production in activated macrophages with IC₅₀ values of 26–40 μM, respectively.     

Antimicrobial Cytochalasan Alkaloids from an Endophytic Fungus Chaetomium globosum

Chemistry of Natural Compounds -