Total synthesis of novel xanthone antibiotics (±)-cervinomycins A₁, and A₂

Abstract

A total synthesis of novel heptacyclic antibiotics cervinomycin A₁ 1 and A₂ 2 following a convergent approach is reported. The cornerstone of our strategy was the construction of the central ring D through photochemical electrocyclization. The oxazolo-isoquinolinone fragment (ABC rings) 7 and the xanthone fragment (EFG rings) 8 were assembled through relatively straightforward synthetic protocols and coupled through a Wittig reaction to give 6 and set up the key photocyclization. Our successful approach to 1 and 2 can be readily adapted to the synthesis of analogues of these interesting antibiotics.