TOTAL SYNTHESIS OF NOVEL XANTHONE ANTIBIOTICS (+ -)-CERVINOMYCINS A(1) AND A(2)/

A total synthesis of novel heptacyclic antibiotics cervinomycin A(1) ( $) under bar 1 and A(2) ($) under bar 2 following a convergent approac h is reported. The cornerstone of our strategy was the construction of the central ring D through photochemical electrocyclization. The oxaz olo-isoquinolinane fragment (ABC rings) ($) under bar 7 and the xantho ne fragment (EFG rings) ($) under bar 8 were assembled through relativ ely straightforward synthetic protocols and coupled through a Wittig r eaction to give ($) under bar 6 and set upthe key photocyclization. Ou r successful approach to ($) under bar 1 and ($) under bar 2 can be re adily adapted to the synthesis of analogues of these interesting antib iotics.