AN EFFICIENT SYNTHESIS OF THE NAPHTHALENE SUBUNITS OF THE PROTEIN-KINASE-C INHIBITOR CALPHOSTIN-C

An efficient synthesis of bromonaphthalenes 5b-c, which represent suitably functionalized precursors to the perylenequinone ring system characteristic of the protein kinase C inhibitor calphostin C (1), is described and was based on the Diels-Alder reaction of omicron-quinol acetate 7 with 1,1,3-trioxygenated butadienes 6a-c, followed by selective, acid-promoted elimination of R3SiOH and AcOH to directly afford naphthalenes 11a-c.