NBS oxidation of 2-substituted furans 9 and 15 followed by further oxidation of the enals with NaClO2 afforded the acids II and 17 in good yields, which are the intermediates of(+)-patulolide A and (-)-pyrenophorin, respectively. Copyright (C) 1996 Elsevier Science Ltd
Efficient Conditions for Conversion of 2-Substituted Furans into 4-Oxygenated 2-Enoic Acids and Its Application to Synthesis of (+)-Aspicilin, (+)-Patulolide A, and (−)-Pyrenophorin
the ester 6. Stereocontrolled reduction of 6 followed by deprotection and the Yamaguchi macrocyclization furnished (+)-aspicilin. For the synthesis of (+)-patulolide (Scheme 3) and (-)-pyrenophorin (Scheme 4), the intermediates are the furans 38 and 44, which were prepared easily by the classical methods using furyllithium 33. The furan ring oxidations proceeded as well, furnishing acids 40 and 46 in