SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
[reaction: see text] The tetracyclic isogeissoschizoid skeleton has been prepared by a novel route that involves the ozonolysis and double reductive amination of a cyclopentene, a nickel-catalyzed cyclization, and a late-stage Fischer indole synthesis.
[reaction: see text] A double ring-closing metathesis reaction for the efficient construction of the fused bicyclic izidine alkaloid skeleton was developed. In this reaction, high selectivity was realized by tuning of electronic and steric effects of substituents in the N-containing tetraenes. It was observed that the reactivity of electron-rich carbon-carbon double bonds is higher than that of electron-deficient ones. A brief mechanistic study is also discussed.
[structure: see text] Azaspirene isolated from the fungus Neosartorya sp. is a novel angiogenesis inhibitor with a 1-oxa-7-azaspiro[4.4]non-2-ene-4,6-dione skeleton. Azaspirene inhibits the endothelial migration induced by vascular endothelial growth factor (ED100 = 27.1 microM).
The highly diastereoselective cascade sequence of three successive thermal pericyclic reactions of 1,2-divinylcyclohexanol allyl and propargyl ethers is described. This novel tandem process provides an efficient synthesis of sesqui- and diterpenoid skeletons having a quaternary carbon at C9. [reaction: see text]
[reaction: see text] The first total synthesis of (+/-)-mycoepoxydiene has been accomplished. A ring-closing olefin metathesis (RCM) approach was employed for the construction of the oxygen-bridged eight-membered bicyclic skeleton. The RCM product was converted to the target natural product featuring the oxidative rearrangement of a furfuryl alcohol introduced as the side chain and the stereoselective 1,2-reduction of a delta-keto-beta,gamma-unsaturated alpha-lactol intermediate.
[reaction: see text] A linear but concise synthetic approach toward the structurally related natural products myriaporone and tedanolide is reported. The route is highlighted by a stereoselective homoallenylboration and a regio- and chemoselective nitrile oxide cycloaddition. Installation of the (Z)-olefin completed the carbon skeleton of myriaporone 1.
[reaction: see text] A short synthesis of the tricyclic skeleton of pleuromutilin is reported, featuring an unusually efficient 8-endo-trig radical cyclization of a xanthate precursor. In the course of this study, a one-carbon ring expansion leading to cycloheptenes was uncovered.
[reaction: see text] An efficient and highly stereocontrolled approach to the 8,10-dimethyl anti-syn-anti-perhydrophenanthrene carbon skeleton starting with the Wieland-Miescher ketone is described. The approach centers on a Diels-Alder-angular methylation-deoxygenation sequence.
[reaction: see text] An efficient entry to the fully elaborated skeleton of vinigrol is described. The installation of the desired stereochemistry at C(12) and the construction of the eight-membered ring were achieved in one operation by a remarkably facile anionic oxy-Cope rearrangement of Z-isopropenyl isomer 24.
[structure: see text] Three novel diterpenes, called cyanthiwigins AB (1), AC (2), and AD (3), were isolated from the Jamaican sponge Myrmekioderma styx. Their structures were elucidated by means of 1D and 2D NMR spectroscopic methods. Cyanthiwigin AC (2) and AD (3) represent novel diterpene-type skeletons.
The hexacyclic himandrine skeleton 5, which is present in the most complex alkaloids of the tropical rain forest tree Galbulimima belgraveana, has been prepared for the first time. The synthesis begins from the known [3.2.1]benzobicyclooctene intermediate 10. Key steps include a Diels-Alder cycloaddition, Curtius rearrangement, Birch reduction, an intramolecular nucleophilic amination, and a palladium-mediated alkene amination. [reaction: see text]
[reaction: see text] The cripowellin ring skeleton, a macrocyclic [2.3.5]-bicyclic ketolactam, was smoothly generated via construction of a spiro(benzazepin-cyclohexane-1,3-dione) employing oxidative cyclization as a key step and a subsequent ring expansion reaction.
A variety of polycyclic ring skeletons (e.g., kigelinol, neoamphilectane, and kempene systems) can be prepared rapidly via intramolecular Diels-Alder cycloadditions (IMDA) of fulvenes. The length of the tethers and the diversity of the substituents on the fulvene core dictate the nature of the IMDA pathway. [reaction: see text]
Maoecrystal V (1), a novel C(19) diterpenoid possessing a unique 6,7-seco-6-nor-15(8-->9)-abeo-5,8-epoxy-ent-kaurane skeleton, was isolated from the leaves of a Chinese medicinal herb, Isodon eriocalyx. Its structure was determined by comprehensive NMR and MS spectroscopic analysis and confirmed by single-crystal X-ray diffraction study. Compound 1 showed remarkable inhibitory activity toward HeLa cells with IC(50) = 0.02 microg/mL (cis-platin: IC(50) = 0.99 microg/mL).
[reaction: see text] An 11-aryl steroid skeleton has been built in one step with a simultaneous introduction of the substituents at both C11 and C10 in 48% overall yield from a trans-allenediyne, whereas a formal Alder ene reaction leading to a bicyclic yne-trienic compound becomes the major process from the cis-allenediyne.
[reaction: see text] Quinovic acid glycosides were microbially deglycosylated by a Nocardia sp. to their aglycon quinovic acid and its biogenetic counterpart, cincholic acid (3), via an unprecedented carbon skeleton rearrangement involving a methyl group migration. The structures of the metabolites were established by ESI-LC/MS and 2D-NMR techniques.
[structure: see text] The first diamino Daphniphyllum alkaloid, daphnipaxinin (1), with an unprecedented hexacyclic fused skeleton, along with a known alkaloid, daphnicyclidin A (2), was isolated from the stem of Daphniphyllum paxianum Rosenth. The structure and absolute stereochemistry of 1 were established by spectral methods, especially two-dimensional NMR techniques and CD analysis.
An efficient, convergent synthesis of the core bicyclo[4.3.1]decane ring system of welwitindolinones is described. Key steps in the synthesis include an intramolecular palladium-catalyzed enolate arylation reaction to create the desired bicyclic skeleton and a Curtius rearrangement to install the bridgehead isocyanate unit. [reaction: see text]