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

A total synthesis of novel heptacyclic antibiotics cervinomycin A(1) ($) under bar 1 and A(2) ($) under bar 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-isoquinolinane fragment (ABC rings) ($) under bar 7 and the xanthone fragment (EFG rings) ($) under bar 8 were assembled through relatively straightforward synthetic protocols and coupled through a Wittig reaction to give ($) under bar 6 and set upthe key photocyclization. Our successful approach to ($) under bar 1 and ($) under bar 2 can be readily adapted to the synthesis of analogues of these interesting antibiotics.