Expedient synthesis of ialibinones A and B by manganese(III)-mediated oxidative free radical cyclisation

The tricyclic natural products ialibinone A and ialibinone B were prepared as a 41:59 mixture in four steps starting from phloroglucinol. The synthetic sequence involved (i) acylation of phloroglucinol under Friedel–Crafts conditions, (ii) double prenylation using phase-transfer methodology, (iii) dearomatising methylation, and (iv) oxidative free radical cyclisation using manganese(III) acetate.