Alkoxide precoordination to rhodium enables stereodirected catalytic hydrogenation of a dihydrofuranol precursor of the C29-40 F/G sector of pectenotoxin-2

An enantioselective synthesis of the stereochemically fully endowed C(29-40) fragment of pectenotoxin-2 is detailed. The highlight of the synthesis is an alkoxide-directed hydrogenation in which ionic complexation of the deprotonated substrate to [Rh(NBD)(DIPHOS-4)]BF4, accomplished by the co-addition of an equivalent of sodium hydride in THF, completely deters a kinetic tendency for dehydration and properly sets the critical stereochemistry at C-35. The dual objectives made possible by this catalytic technology are expected to have far-ranging applications.