Stereodivergent and Reiterative Synthesis of Bistetrahydrofuran Ring Cores of Annonaceous Acetogenins

Eight diastereoisomers of the bistetrahydrofuran ring cores of annonaceous acetogenins have been synthesized by asymmetric alkynylation of α‐tetrahydrofuranic aldehydes and stereodivergent one‐pot tetrahydrofuran (THF) ring formation. In all cases, the asymmetric alkynylation proceeded with very high diastereoselectivity to give eight kinds of optically pure THF cores. We also describe a comparison of the 1H and 13C NMR spectral data of the eight isomers and give full details of the THF ring construction. Bistetrahydrofuran ring cores of annonaceous acetogenins have been synthesized by utilizing asymmetric alkynylation of α‐tetrahydrofuranic aldehydes and stereodivergent one‐pot tetrahydrofuran ring formation (see scheme). In all cases, the asymmetric alkynylation proceeded with very high diastereoselectivity to give eight optically pure THF cores.