Stereoselective synthesis of 4-dehydroxydiversonol employing enantioselective palladium-catalysed domino reactions.

The stereoselective synthesis of 4-dehydroxydiversonol (4) employing enantioselective palladium-catalysed domino processes such as the domino Wacker-Heck and the domino Wacker-carbonylation reaction for the formation of the central chroman moiety is described. Thus, reaction of 8 with palladium(II) trifluoroacetate [Pd(OTFA)2] in the presence of carbon monoxide, methanol and the 2,2'- bis(oxazolin-2-yl)-1,1'-binaphthyl (BOXAX) ligand 17 led to 19 in 80% yield and 96% ee. Similarly, the chroman 7 was prepared using 8 and methyl acrylate (9) as starting material. Hydrogenation of the double bond, oxidation of the benzylic methylene group and intramolecular acylation of chromanone 6 provided the tetrahydroxanthenone core 5, from which the synthesis of 4 was completed. The relative configuration of 4 could be established by crystal structure analysis.