Sulfur-Substituted Dienes and the Silylene Protecting Group in Synthesis. Deoxypillaromycinone

Article abstract of DOI:10.1021/jo00167a020

A general approach directed toward the anthracycline antitumor compounds and the tetracycline antibiotics evolves from the sequential use of a 1-oxy- and 2-oxybuta-1,3-diene in regiocontrolled Diels-Alder reactions with juglone.By appropriately choosing the 1-(acyloxy)buta-1,3-diene, the absolute as well as relative stereochemistry of the final products is controlled. 2-Acetoxy-3-p-anisylthiobuta-1,3-diene controlls the orientation of the second cycloaddition and permits direct introduction of the enone functionality.The success of this second Diels-Alder reaction with a very sensitive cyclohexenone as a dienophile attests to its extraordinary reactivity and therefore utility in synthesis.The elaboration of the A ring functionality of pillaromycinone employs a cis hydroxylation and conversion of the cyclohexanone unit to a 1-acetylcyclohexene system via singlet oxygen oxidation of a homologated enol ether.Aromatization then completes the synthesis of deoxypillaromycinone.The virtues of the di-tert-butylsilyl protecting group for 1,2- and 1,3-diols are summarized.