ABSTRACT
A platinum(II)-catalyzed asymmetric ring opening of oxabenzonorbornadienes with phenols was developed, which afforded the corresponding cis-2-(un)substituted phenoxy-1,2-dihydronaphthalen-1-ol products rather than the trans ones in excellent yields (up to 99%) with moderate to good enantioselectivities (up to 87% ee) under mild conditions. In addition, the cis-configuration of product 2b was confirmed by X-ray diffraction analysis. Based on the results, a potential mechanism for the present catalytic reaction was proposed.
ABSTRACT
A novel asymmetric ring-opening reaction of N-substituted azabenzonorbornadienes with a wide variety of substituted benzyl alcohols and the addition reaction of N-substituted azabenzonorbornadienes with thiols are reported, affording the corresponding 1,2-trans-alkoxyamino products in moderate yields with excellent enantioselectivities (up to 94% ee) and the corresponding thiol addition products in high yields with lower enantiomeric excesses (ee) in the presence of iridium catalyst, respectively. The effects of ligands, catalyst loading, solvents and additives, and temperature were also investigated. The anti-configuration of the product 3c was confirmed by X-ray crystal structure analysis. A possible mechanism for the present catalytic reaction is proposed.
Subject(s)
Alcohols/chemistry , Alkenes/chemistry , Amines/chemical synthesis , Aza Compounds/chemistry , Bridged Bicyclo Compounds/chemistry , Iridium/chemistry , Organometallic Compounds/chemistry , Amines/chemistry , Catalysis , Models, Molecular , Molecular StructureABSTRACT
A new hTopo I isomerase inhibitor, (+)-3,3',7,7',8,8'-hexahydroxy-5,5'-dimethylbianthraquinone (2240A), was isolated from the mangrove endophytic fungus no. 2240 collected from an estuarine mangrove at the South China Sea coast. Its structure was elucidated by spectral analyses including two-dimensional NMR, HR-EI-MS, IR, and UV. The hTopo I isomerase inhibition experiment showed that 2240A (1) possessed strong inhibiting activity. When its inhibition concentration was 4.65 micromol/l, its percent inhibition rate was 59.1%, while the lowest inhibition concentration of the positive control camptothecin was 1.00 x 10(3) micromol/l.
Subject(s)
Anthraquinones/chemistry , Anthraquinones/pharmacology , Fungi/chemistry , Topoisomerase I Inhibitors , Humans , Molecular StructureABSTRACT
Two new metabolites, named no. 2106 A (1) and cyclo-(N-MeVal-N-MeAla) (2), have been produced by the endophytic fungus no. 2106 isolated from the seeds of the mangrove Avicennia marina in Hong Kong. The structures were elucidated by 2D NMR, HR-MS, and X-ray diffraction analyses.
Subject(s)
Avicennia/microbiology , Fungi/chemistry , Heterocyclic Compounds, 2-Ring/chemistry , Peptides, Cyclic/chemistry , Models, Molecular , Molecular StructureABSTRACT
Four new aromatic allenic ethers, (7E)-3-(4-buta-2,3-dienyloxy-3-methoxy-phenyl)-acrylic acid methyl ester (1), (7E)-3-[4-(4-buta-2,3-dienyloxy-benzyloxy)-phenyl]-acrylic acid methyl ester (2), 4-(4-buta-2,3-dienyloxy-benzyloxy)-benzoic acid methyl ester (3), (7E)-3-[4-(4-buta-2,3- dienyloxy-benzyloxy)-3-methoxy-phenyl]-acrylic acid methyl ester (4) were isolated from the fungus Xylaria sp. No. 2508. The structures of those compounds were determined by analysis of spectroscopic data, mainly 2D NMR experiments.
Subject(s)
Ethers/isolation & purification , Xylariales/chemistry , Ethers/chemistry , Molecular StructureABSTRACT
Twelve allenic aromatic ethers, some of them are natural products isolated from the mangrove fungus Xylaria sp. 2508 in the South China Sea, were synthesized. Their antitumor activities against KB and KBv200 cells were determined. All these compounds demonstrated cytotoxic potential, ranging from weak to strong activity. The analysis of structure-activity relationships suggested that the introduction of allenic moiety could generate or enhance cytotoxicity of these phenol compounds.
