The synthesis of a new class of multisubstrate adduct inhibitors of polyamine biosynthesis has been investigated. The first target compound, designed to inhibit spermidine synthase, was obtained and proved to be a very potent inhibitor of that enzyme. Two synthetic routes to effect the coupling of the polyamine spermidine to the nucleoside adenosine were studied. The first route involved a proposed Wittig or Julia olefination reaction to form the critical 5'- ...