Diels-Alder Approaches to Model Compounds Related to Fredericamycin A

Article abstract of DOI:10.1021/jo00258a022

A series of model compounds related to the antitumor and antibiotic compound fredericamycin A has been prepared.Spiro<3-cyclopentene-1,1'-indan>-2,5-dione (2) has been prepared and established as a novel spiro dienophile in the Diels-Alder reaction with 1,3-butadiene, Danishefsky's diene, a triacetoxy-substituted o-quinodimethane, and two isobenzofuran intermediates.Thus, the cycloaddition of 3-cyano-4,5,7-trimethoxy-1(3H)-isobenzofuranone (35) and 2 afforded 4,9-dihydroxy-5,6,8-trimethoxyspiro<2H-benzindene-2,1'-indan>-1,3-dione (38) in 62percent yield.This methodology provides a viable synthetic route to the quinone portion of fredericamycin A that contains the seven requisite oxygens.