Clickable chemical tools are essential for studying the localization and role of biomolecules in living cells. For this purpose, alkyne-based close analogs of the respective biomolecules are of outstanding interest. Here, in the field of phytosterols, we present the first alkyne derivative of sitosterol, which fulfills the crucial requirements for such a chemical tool as follows: very similar in size and lipophilicity to the plant phytosterols, and correct absolute configuration at C-24. The alkyne sitosterol FB-DJ-1 was synthesized, starting from stigmasterol, which comprised nine steps, utilizing a novel alkyne activation method, a Johnson-Claisen rearrangement for the stereoselective construction of a branched sterol side chain, and a Bestmann-Ohira reaction for the generation of the alkyne moiety.
Keywords: Johnson–Claisen rearrangement; alkyne; click chemistry; imaging; phytosterols; sitosterol.