Four Hydrogen Bonds − DDAA, DADA, DAAD and ADDA Hydrogen Bond Motifs

Receptor molecules containing four hydrogen‐bond acceptor or donor sites based on aminopyridines, aminonaphthyridines and urea subunits have been synthesized and their association has been investigated. DDAA ( 13a − c ) and DADA ( 18a − b ) arrays may form homodimers, while DAAD ( 24a − d ) with ADDA ( 25a − b ) may form heterodimers. While most parent heterocycles were only slightly soluble in standard organic solvents, substitution was able to enhance the solubility in most cases. The naphthyridine 24d , bearing a substituent derived from lysine, possesses potential anchor groups for a covalent connection. Binding studies were carried out in chloroform and monitored by 1 H NMR, and the binding constants K ass for the heterodimers DAAD·ADDA ( 24·25 ) were compared to the binding of smaller (ADD, 26 ) or mismatching (DADD, 27 ) counterparts, showing that the matching heterodimer is formed with a selectivity of > 50. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2002)