FUNDAMENTAL PRINCIPLES OF BLOCK DESIGN AND ASSEMBLY IN THE PRODUCTIONOF LARGE, RIGID MOLECULES WITH FUNCTIONAL UNITS (EFFECTORS) PRECISELYLOCATED ON A CARBOCYCLIC FRAMEWORK

New cycloaddition reactions have been developed to regiospecifically c ouple together alicyclic reagents (BLOCKs)(2) containing the same or d ifferent functional units (effectors(3)). Dipolar cycloadditions (alke nes plus cyclobutene epoxides and the related aziridines), Diels-Alder cycloadditions (alkenes plus dienes formed from s-tetrazine, 1,2,4-tr iazine and 1,3,4-oxadiozole) and condensations of alpha-diones with vi c-diamines have been used as the coupling procedures. This new approac h is based on a building BLOCK strategy(2) where small BLOCKs already containing an attached effector are joined in a simple convergent step to produce large rigid structures (ribbon molecules(4)) containing on e or more effector groups precisely positioned both in distance and re lative orientation onto an inert carbocyclic frame (a molrac(5)). Thes e effector groups include, porphyrins, crown ethers, fluorophores, nuc leic acid bases, beta-lactams, redox-active components, bidentate liga nds of various type, amino acids, intercalators, and metal complexes. All these classes can be joined together either as homo or mixed pairs into rods, spacers or U-shaped cavity structures, whose shapes can be evaluated using molecular modelling (AM1, Syby1, PM3 etc.).