P. Vogel
2007
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0
Influential Citations
4
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Journal
Journal name not available for this finding
Abstract
Double exocyclic 1,3-dienes such as 2,3,5,6-tetramethylidene-7-oxabicyclo[2.2.1]heptane and its 1-substitutedderivatives undergo two successive Diels–Alder additions with large reactivity difference betweenthe addition of the first equivalent (k 1) andthe second equivalent (k 2) of dienophile. Thisallows one to prepare, through parallel synthesis, a large number of linearly condensed polycyclicsystems containing three annulated six-membered rings, including naphthacenyl systems and anthracyclinones.The large k 1/k 2rate constant ratio is a consequence of the Dimroth principle, the first cycloaddition being significantlymore exothermic then the second one. Control of regio- and stereoselectivity of the two successive cycloadditionsis possible by 1-substitution of the 2,3,5,6-tetramethylidene-7-oxabicyclo[2.2.1]heptane, for instance bya 1-(dimethoxymethyl) group, or by stereoselective disubstitution of the double diene by arenesulfenylsubstituents. Enantiomerically pure anthracyclinones and analogues are obtained using enantiomericallypure dienophiles such as 3-oxo-but-2-en-2-yl esters. The chemistry so-developed has allowed the preparationof enantiomerically pure 6-((aminoalkoxy)oxy)methyl-6,7-dideoxyidarubicinones that are DNA intercalatorsand inhibitors of topoisomerase II-induced DNA strained religation.