A short synthesis of deoxyfrenolicin

Abstract

Oxidative rearrangement of furo[3, 2-b]naphtho[2, 1-d]furan 8 using CAN provided an efficient route to the hemiacetal 9 which has a three-ring system in common with that in the natural products frenolicin A 1, frenolicin B 2 and deoxyfrenolicin 3. Attempted reduction of the hemiacetal 9 to the cis-lactone 11 using triethylsilane and trifluoroacetic acid was unsuccessful, however, hydrogenation of the hemiacetal 9 not only effected reduction of the hemiacetal group to a cyclic ether but also hydrogenolysis of the γ-lactone to the ring-opened carboxylic acid which was conveniently characterised as its methyl ester 13. Deprotection of the methyl ether 13 to the naphthol 15 using boron tribromide also effected cis-trans epimerisation at C-1 thus completing a synthesis of deoxyfrenolicin 3 upon hydrolysis of the methyl ester to the carboxylic acid.