The preparation of a tetradeoxy anthracyclinone is described. The key reaction is the cyclization of the acetylenic coumarin 10 to anthraquinone 11. Interestingly, the related model system 12 failed to cyclize. The transformation of 11 into the desired compound 13 was effected by straightforward reactions. The key intramolecular cyclization reaction is also useful for the preparation of phthalide quinone 7.
Available at: http://works.bepress.com/george_kraus/104/