The rational design and synthesis of a biochemical probe of natural (+)-macrosphelide A, a potent cell–cell adhesion inhibitor, was completed to aid in the identification of its biological target. The key features of the synthesis include: (1) an efficient synthesis of the macrosphelide core structure using Yamaguchi–Hirao alkynylation, (2) a cross metathesis to connect a linker unit to the allyl-macrosphelide and (3) coupling of the linker-bound macrosphelide A with a chemical biotin tag.