Synthesis of the bicyclic dienone core of the antitumor agent ottelione B
作者:Derrick L. J. Clive、Stephen P. Fletcher
DOI:10.1039/b205753k
日期:2002.8.21
The intramolecular Diels-Alder adduct 12 was converted via dimesylate 20 into dienone 7, which represents the unusual, and apparently quite stable, core of the antitumoragent ottelione B (1).
yield. The bromine atom-transfer radical addition in benzene was not satisfactory. The addition proceeded smoothly in polar solvents such as DMF and DMSO, protic solvents such as 2,2,2-trifluoroethanol and 1,1,1,3,3,3-hexafluoro-2-propanol, and aqueous media. Ab initio calculations were conducted to reveal the origin of the solvent effect of water in the addition reaction. The polar effect of solvents
diastereoselective method was developed for the [2,3]-sigmatropic rearrangement of N-allyl ammonium ylides, affording products in up to 95% isolated yields and up to 97:3 dr; most of the desired products were formed within 1 minute. For the asymmetric reaction, a chiral auxiliary was introduced to the starting compound, affording the rearrangement product with high diastereoselectivities. A rapid and diastereoselective
A short approach to the bicyclo[4.3.0]nonane fragment of stawamycin
作者:Luiz C. Dias、Gliseida Z. Melgar、Luciana S.A. Jardim
DOI:10.1016/j.tetlet.2005.05.004
日期:2005.6
The bicyclo[4.3.0]nonane (C11–C21) fragment of stawamycin has been prepared by a sequence involving 11 steps (10% overall yield) from methyl (R)-(−)-3-hydroxy-2-methylpropionate. Key steps are a Pd-catalysed Stille coupling reaction between a vinyl iodide and a vinyl stannane followed by an intramolecular Diels–Alder cycloaddition reaction to give the desired adduct as the major isomer in 21% overall
Lewis Acid-Promoted Kharasch−Curran Additions: A Competition Kinetics Study of Bromine Atom Transfer Addition of <i>N</i>-α-Bromoacetyl-oxazolidinone to 1-Hexene
作者:Hao Feng、Ivanka K. Kavrakova、Derek A. Pratt、Joel Tellinghuisen、Ned A. Porter
DOI:10.1021/jo0201676
日期:2002.8.1
experiments were carried out in both solvent systems with added carbontetrachloride to study how Lewis acid affected the product distribution. In the presence of carbontetrachloride, chloride 7 is formed in addition to 6 and the ratio of these two products depends on the amount of Lewis acid present. In the presence of ytterbium triflate, in the cosolvent system, the reaction rate of bromine atom transfer