A C-glycosidation approach to the central core of amphidinol 3: synthesis of the c39-c52 fragment.

[reaction: see text] A concise route to an advance precursor (3) of the central core of amphidinol 3, a natural occurring polyketide, has been developed by applying a reductive lithiation as key step. The origin of the diastereoselectivity of this reaction was comprehensively studied for nucleophilic C-glycoside donor 5 and differently protected analogues.