Determination of the Absolute Configuration of the Pseudo-Symmetric Natural Product Elatenyne by the Crystalline Sponge Method

Elatenyne is a marine natural product that was isolated in 1986. Despite its simple 2,2′‐bifuranyl backbone, its relative structure was only recently determined. The absolute configuration of elatenyne has still not been unequivocally confirmed because of its pseudo‐meso core structure, which results in a specific rotation, [α]D , of almost zero. In this work, the structure of natural elatenyne was determined by the crystalline sponge method and the use of a porous coordination network (a crystalline sponge) capable of absorbing organic guests; in the sponge, the absorbed guests are ordered and crystallographically observable. The crystalline sponge could differentiate between the two very similar alkyl side chains, and the absolute structure of elatenyne was thus reliably determined. The total amount required for the experiments was only approximately 100 μg, and the majority (95 μg) could be recovered after the experiments. The structure of natural elatenyne, which was first isolated 30 years ago, was determined by the use of a porous coordination network (a crystalline sponge) capable of absorbing organic guests. The crystalline sponge differentiates between the two very similar alkyl side chains, and the absolute structure of elatenyne was thus reliably determined.