Solution Phase Combinatorial Chemistry. Discovery of Novel Polyazapyridinophanes with Potent Antibacterial Activity by a Solution Phase Simultaneous Addition of Functionalities Approach

Chemical modification of pre-formed asymmetric polyazaphane scaffolds by simultaneous addition of functionality (letters) in solution has been developed for the preparation of tertiary nitrogen-based combinatorial chemistry libraries. This approach has some significant advantages over the more commonly employed solid phase bead splitting/reaction/mixing procedures for the preparation of libraries. Three novel, asymmetric polyazaphanes 32, 33, and 37 have been synthesized in high yields by an efficient cyclization of 2,6-bis(bromomethyl)pyridine (31) with new orthogonally protected triamines 29, 30, and 35, respectively. Selective deprotection of 32, 33, and 37 provided mono-t-Boc-protected scaffolds 1−3 suitable for solution phase, simultaneous addition of functionalities. Model studies of small libraries of scaffold 2 using CZE analyses indicated that simultaneous addition of 10 benzylic bromide alkylating functionalities would result in libraries containing approximately equimolar amounts of all possible compounds. Sixteen purified tertiary amine libraries 4−19 (total complexity of 1600 compounds) were generated by this procedure from scaffold 2. A “fix-last” combinatorial method was devised to minimize chemical reactions. Several first-round sublibraries of scaffold 2, containing a mixture of 100 compounds, exhibited potent antimicrobial activities. Twenty single compounds 63−82 with uniform functionalities at the combinatorialized sites were synthesized. Some of these pure compounds were more active, while others were less active, compared with the parent mixtures 5 and 10.