Novel Isomerically Pure Tetrasubstituted Allylboronates: Stereocontrolled Synthesis of α-Exomethylene γ-Lactones as Aldol-Like Adducts with a Stereogenic Quaternary Carbon Center
作者:Jason W. J. Kennedy、Dennis G. Hall
DOI:10.1021/ja016391e
日期:2002.2.1
1-alkoxycarbonyl vinylcopper(I) intermediates from the conjugate addition of organocuprates onto acetylenic esters were trapped with very high cis-addition selectivity with iodomethylboronic esters in the presence of HMPA. The resulting isomerically pure 3,3-disubstituted allylboronates react with aldehydes in a highly diastereo- and enantioselective manner, providing α-exomethylene γ-lactones with a stereogenic
Lewis Acid Catalyzed Allylboration: Discovery, Optimization, and Application to the Formation of Stereogenic Quaternary Carbon Centers
作者:Jason W. J. Kennedy、Dennis G. Hall
DOI:10.1021/jo049773m
日期:2004.6.1
A full account of the development of the first catalytic manifold for the additions of allylboronates to aldehydes is described. The thermal additions (both diastereospecific and enantioselective) of 2-carboxyester 3,3-disubstituted allylboronates 1 to both aromatic and aliphatic aldehydes give biologically and synthetically important exo-methylene butyrolactones 2 containing a β-quaternary carbon
2-Methylene-4-butyrolactones were conveniently synthesized by treatment of an aldehyde with 2-carboethoxyallyl(-ic) bromide and metallic tin (and aluminum) in good yields. Protolichesterinic acid was synthesized by employing the method.
[reaction; see text] A general and practical procedure for the highly diastereoselective preparation of either the cis- or trans-beta,gamma-disubstituted-gamma-butyrolactones by appropriate choice of Lewis or Bronsted acid catalysts during crotylboration or lactonization is reported. The cis-stereochemistry of the Z-crotylboration product can be inverted with strong acids during lactonization. A carbocation
Synthesis and cytotoxic activity of γ-aryl substituted α-alkylidene-γ-lactones and α-alkylidene-γ-lactams
作者:Anna Albrecht、Jacek F. Koszuk、Jakub Modranka、Marek Różalski、Urszula Krajewska、Anna Janecka、Kazimierz Studzian、Tomasz Janecki
DOI:10.1016/j.bmc.2008.03.035
日期:2008.5
A series of 5-aryl-3-alkylidenedihydrofuran-2(3H)-ones 6a-g'' and 11a,b as well as 5-aryl-3-methylidenepyrrolidin-2-ones 10a-c and 12 were synthesized starting from 4-aryl-2-diethoxyphosphoryl-4-oxobutanoates 3a-g. Reaction sequence includes reduction or reductiveamination of the carbonyl group, lactonization or lactamization step and finally the Horner-Wadsworth-Emmons olefination of aldehydes using