
%0 Journal Article
%A Rozek, Tomas 
%A Janowski, Wit 
%A Hevko, John M. 
%A Tiekink, Edward R. T. 
%A Dua, Suresh 
%A Stone, David J. M. 
%A Bowie, John H. 
%T Syntheses of Angucyclinones Related to Ochromycinone
%J Australian Journal of Chemistry
%D 1998/06/03
%V 51
%N 6
%P 515-524
%K 
%R https://doi.org/10.1071/C97151
%U https://www.publish.csiro.au/paper/C97151 
%X Two synthetic approaches have been investigated for the syntheses of model angucyclinones related to ochromycinone. The first involves a Diels&#8211;Alder/Friedel&#8211;Crafts strategy in which the Diels&#8211;Alder adduct formed between dimethyl acetylenedicarboxylate and 3-ethenyl-5,5-dimethylcyclohex-2-en-1- one was converted into 6,6-dimethyl-8-oxo-5,6,7,8-tetrahydronaphthalene-1,2-dicarboxylic anhydride, which was then reacted with benzene in a Friedel&#8211;Crafts reaction. Acid-catalysed cyclization of the Friedel&#8211;Crafts products gave 3,3-dimethyl-3,4-dihydrobenz&#91;a&#93;anthracene-1,7,12(2H)-trione (3) in poor yield. Angucyclinones related to (3) are formed (in 40&#8211;50% overall yield) by aromatization of the adduct formed between the appropriate 1,4-naphthoquinone and 3-&#91;(E)-2-methoxyethenyl&#93;- 5,5-dimethylcyclohex-2-en-1-one (this dienone reacts with itself by a Diels&#8211;Alder process to yield an adduct which decomposes to 3,3,8,8-tetramethyl-3,4,7,8-tetrahydroanthracene-1,6(2H,5H)-dione). When the substituted 1,4-naphthoquinone is unsymmetrical, a boron triacetate assisted Diels&#8211;Alder reaction gives a single regioisomer (e.g. X-ray investigations indicate that 8-hydroxy-3,3-dimethyl-3,4-dihydrobenz&#91;a&#93;anthracene-1,7,12(2H)-trione is the product from 5-hydroxy-1,4-naphthoquinone). An X-ray structural study of the Diels&#8211;Alder adduct in the above reaction confirms the operation of an endo cyclization. 
