Total Syntheses of the Structures Assigned to Denigrins A, B, C, F, and G, 3,4-Diaryl-Pyrrole and -Pyrrolidinone Alkaloids, and the Conversion of Congener B into the Co-metabolite Spirodactylone.

The title marine natural products have been prepared by total synthesis and in the case of congeners 3 , 6 , and 7 for the first time. Each of these was obtained by manipulation of readily prepared denigrin B ( 2 ). The structure, 3 , assigned to denigrin C is shown to be incorrect. Reaction of compound 2 with DDQ has led, in high yield, to the related natural product spirodactylone ( 16 ), while treating the corresponding permethyl ether 15 with PIFA/BF 3 ·Et 2 O provides compound 20 , embodying an isomeric framework.