Cationic and Fluorescent “Janus” Dendrimers Sabine Fuchs, † Anna Pla-Quintana, † Serge Maze `res, ‡ Anne-Marie Caminade,* ,† and Jean-Pierre Majoral* ,† Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse Cedex 4, France, and Institut de Pharmacologie et de Biologie Structurale, 205 route de Narbonne, 31077 Toulouse Cedex 4, France caminade@lcc-toulouse.fr; majoral@lcc-toulouse.fr Received July 25, 2008 ABSTRACT Two synthetic routes to “Janus”-type dendrimers possessing ammonium groups on one side and fluorescent dansyl derivatives on the other side are described. These surface-block dendrimers are obtained by the coupling of two different dendrons, built from the hexafunctional cyclotriphosphazene core. Their characterization and their photophysical behavior are reported. The largest compound possesses 10 ammonium groups and 5 dansyl groups; it is potentially useful as a fluorescent label in materials science and biology. The art of designing dendritic macromolecules progresses toward the synthesis of more and more sophisticated com- pounds, 1 including those having several types of terminal groups, precisely placed in different areas of the surface. Such compounds can be called “Janus” or surface-block dendrim- ers. Examples of the synthesis of some of these compounds have already been described, 2 often for using them for self- assembly 3 or as liquid crystals. 4 However, to the best of our knowledge, there is no example to date of surface-block dendrimers bearing fluorescent entities on one side and water- solubilizing functions on the other, which should be useful for labeling materials or biological entities. The key point for the synthesis of such dendrimers is the coupling of two different dendrons by their core. This strategy is relatively difficult to apply when dealing with reactive terminal groups, due to problems of compatibility with the core functionality. Another problem is the relatively small number of terminal groups for low-generation den- drons: one arm is for future coupling and not for growing, thus it is necessary to build relatively high generations to † Laboratoire de Chimie de Coordination du CNRS. ‡ Institut de Pharmacologie et de Biologie Structurale. (1) Newkome, G. R.; Shreiner, C. D. Polymer 2008, 49, 1–173. (2) (a) Feng, Y.; He, Y. M.; Zhao, L. W.; Fan, Q. H. Org. Lett. 2007, 9, 2261–2264. (b) Grayson, S. M.; Fre ´chet, J. M. J. J. Am. Chem. Soc. 2000, 122, 10335–10344. (c) Maraval, V.; Laurent, R.; Donnadieu, B.; Mauzac, M.; Caminade, A. M.; Majoral, J. P. J. Am. Chem. Soc. 2000, 122, 2499–2511. (3) (a) Bury, I.; Donnio, B.; Gallani, J. L.; Guillon, D. Langmuir 2007, 23, 619–625. (b) Maraval, V.; Maraval, A.; Spataro, G.; Caminade, A. M.; Majoral, J. P.; Kim, D. H.; Knoll, W. New J. Chem. 2006, 30, 1731–1736. (c) Percec, V.; Imam, M. R.; Bera, T. K.; Balagurusamy, V. S. K.; Peterca, M.; Heiney, P. A. Angew. Chem., Int. Ed. 2005, 44, 4739–4745. (d) Luman, N. R.; Grinstaff, M. W. Org. Lett. 2005, 7, 4863–4866. (4) (a) Bury, I.; Heinrich, B.; Bourgogne, C.; Guillon, D.; Donnio, B. Chem.-Eur. J. 2006, 12, 8396–8413. (b) Saez, I. M.; Goodby, J. W. Chem.-Eur. J. 2003, 9, 4869–4877. ORGANIC LETTERS 2008 Vol. 10, No. 21 4751-4754 10.1021/ol801698k CCC: $40.75  2008 American Chemical Society Published on Web 09/25/2008