Asymmetric Total Syntheses of Tuberostemonine, Didehydrotuberostemonine, and 13-Epituberostemonine
摘要:
Detailed experimental approaches toward the pentacyclic Stemona alkaloids tuberostemonine and didehydrotuberostemonine and the close analogue 13-epituberostemonine are described. The syntheses originate with a hydroindolinone derivative that can be obtained on a large scale in a single step from carbobenzoxy-protected L-tyrosine. Highlights of the conversion of this hydroindolinone to the target structures are the three-fold use of ruthenium catalysts, first in azepine ring-closing metathesis and then in alkene isomerization and cross-metathesis propenyl-vinyl exchange, as well as the stereoselective attachment of a y-butyrolactone ring to a tetracycle core structure by use of a lithiated asymmetric bicyclo[3.2.1]octane (ABO) ortho ester. Structural analysis by density functional theory (DFT) methods revealed that the ease of oxidation of the natural product is likely due to the conformational preferences of the pyrrolidine and the fused cyclohexane rings.
[EN] METHOD FOR THE PREPARATION OF 1-ARYL-1-ALKYL-2-ALKYL-3-DIALKYLAMINOPROPANE COMPOUNDS [FR] PROCÉDÉ DE PRÉPARATION DE COMPOSÉS 1-ARYL-1-ALKYL-2-ALKYL-3-DIALKYLAMINO-PROPANE
A new approach to prostanoid synthesis: a model study
作者:Jih Ru Hwu、Jeffrey A. Robl
DOI:10.1039/c39860000704
日期:——
The first successful intramolecular nitrone–alkene cycloaddition involving a C-alkenyl nitrone in which the reacting centres are separated by two carbon atoms was applied to the construction of the nuclei of prostaglandin H analogues.
N-dimethylbenzamide with phosphorus oxychloride. The cycloaddition reactions of these 2-trifluoromethyl-1,3-diazabutadienes with DMAD and phenylacetyl chloride provided 2-trifluoromethylpyrimidine derivatives in regular to moderate overall yield. A methodology to prepare 2-trifluoromethylpyrimidines has been developed on the basis of a cyclization reaction of 2-trifluoromethyl-1,3-diazabutadienes. These
作者:Luisruben P. Martinez、Shigenobu Umemiya、Sarah E. Wengryniuk、Phil S. Baran
DOI:10.1021/jacs.6b04816
日期:2016.6.22
The structurally intriguing terpenes pallambins C and D have been assembled in only 11 steps from a cheap commodity chemical: furfuryl alcohol. This synthesis, which features a redox-economic approach free of protecting-group manipulations, assembles all four-ring systems via a sequential cyclization strategy. Of these four-ring constructing operations, two are classical (Robinson annulation and Mukaiyama
Influence of the trimethylsilyl group on the diastereoselectivity of an adjacent Claisen amide-acetal rearrangement
作者:Eward H. Smith、Nicholas D. Tyrrell
DOI:10.1039/c39830000285
日期:——
In contrast to their reactions with other (E)-allylic alcohols, the amide-acetals (1a, b) react with (E)-1-trimethylsilylpent-3-en-2-ol to give mixtures of product amides in which the threo-diasteroisomers marginally predominate.
作者:Jack A. Maddison、Peter W. Seale、Edward P. Tiley、William K. Warburton
DOI:10.1039/p19740000081
日期:——
Some trans-phenylazoformamide oximes (4) have been prepared from trans-benzenediazocyanides (3) and hydroxylamine, and converted into trans-3-phenylazo-1,2,4-oxadiazoles (5) by reaction with amide acetals or trialkyl orthoformates. Some 5-unsubstituted 3-phenylazo-1,2,4-oxadiazoles have been reduced to 3-amino-1-aryl-1,2,4-triazoles (8), but di-imide reduced 3-p-chlorophenylazo-1,2,4-oxadiazole to