Concise synthesis of complicated polypropionates through one-pot dissymmetrical two-directional chain elongation.

Herein, a major breakthrough in a sulfur dioxide-mediated oxyallylation cascade reaction is reported that allows the preparation of complex long-chain polyketide fragments with more than ten stereogenic centers through a carefully designed desymmetrization process. An allylbissilane is combined, under the appropriate reaction conditions, with two different 1,3-dioxy-1,3-dienes permitting the construction of a 13-membered polypropionate precursor in one pot. Four stereocenters are selectively created during this process. The so-obtained pseudo-C(2)- or -C(S)-symmetric products are desymmetrized through selective deprotection and can be selectively elongated in both directions using aldol chemistry.