Synthesis of the ABCD fragment of gymnocin-B

[Display omitted] •Synthetic study of naturally occurred pentadecacyclic ether gymnocin-B.•Convergent synthesis of the ABCD fragment of gymnocin-B is accomplished using the oxiranyl anion strategy.•The five-membered A ring is constructed via a stereoselective radical cyclization of a neopentyl-type iodide. A convergent synthesis of the ABCD fragment of gymnocin-B was accomplished. The tetracyclic ether ring system was synthesized by the construction of the BC ring system via the oxiranyl anion alkylation and ring expansion reaction, followed by the formation of the five-membered A-ring via a stereoselective radical cyclization reaction of a neopentyl-type iodide.