Molecular Objects DOI: 10.1002/anie.201005164 The Largest Synthetic Structure with Molecular Precision: Towards a Molecular Object** Baozhong Zhang, Roger Wepf, Karl Fischer, Manfred Schmidt, SØbastien Besse, Peter Lindner, Benjamin T. King, Reinhard Sigel, Peter Schurtenberger, Yeshayahu Talmon, Yi Ding, Martin Kröger, Avraham Halperin, and A. Dieter Schlüter* Since the advent of their discipline, organic chemists have sought to imitate biology through synthesis. This challenge combines four themes: chemical structure, [1] function, [2] size, [3] and molecular shape. [4] While structure and function are better understood, size and shape remain challenging. So far, chemists have not succeeded at making well-defined mole- cules as large as those found in biology—the highest- molecular-weight structurally precise synthetic polymer, a polystyrene, has a mass of only 40  10 6 Da, [5] a tiny fraction of the size of the largest DNA molecules. The control of shape in large synthetic molecules is even less advanced. This feat is routine for biology—even the simplest organisms have well- defined shapes, as exemplified by the rodlike tobacco mosaic virus (TMV). Indeed, to the chemist, the TMV is a paragon : a massive supramolecule with perfect control of chemical structure, function, size, and molecular shape. We report herein a dendronized polymer [6] that approximates the size and cylindrical shape of the TMV, thus advancing these chemical frontiers. Our synthesis relies on standard polymer- ization methods followed by radial expansion by using methods pioneered by Vögtle [7] and Tomalia. [8] First-gener- ation dendrons were affixed to peripheral amino groups of the fourth-generation dendronized polymer, PG4 long , [9] by using Scheme 1. Synthesis of PG5. Chemical structure of the starting poly- mers PG4 short and PG4 long and their conversion to the fifth generation by deprotection and reaction with the active ester dendron 1. [*] Dr. B. Zhang, Prof. A. D. Schlüter Department of Materials, Institute of Polymers Swiss Federal Institute of Technology, ETH Zürich HCI J 541, 8093 Zürich (Switzerland) Fax: (+ 41) 44-633-1395 E-mail: ads@mat.ethz.ch Dr. R. Wepf EMEZ (Electron Microscopy), ETH Zurich (Switzerland) Dr. K. Fischer, Prof. M. Schmidt Institut für Physikalische Chemie, Universität Mainz (Germany) Dr. S. Besse Agroscope Changins-Wädenswil Research Station ACW, Nyon (Switzerland) Dr. P. Lindner Institute Laue Langevin, Grenoble (France) Prof. B. T. King Department of Chemistry, University of Nevada, Reno(USA) Dr. R. Sigel, Prof. P. Schurtenberger [+] University of Fribourg, Adolphe Merkle Institute and Fribourg Center for Nanomaterials, Marly (Switzerland) Prof. Y. Talmon Department of Chemical Engineering Technion-Israel Institute of Technology, Haifa (Israel) Dr. Y. Ding, Prof. M. Kröger Department of Materials, Polymer Physics ETH Zurich (Switzerland) Prof. A. Halperin Laboratoire de SpectromØtrie Physique (LSP) CNRS UniversitØ Joseph Fourier, Saint Martin d’Hres (France) [ + ] Current address: Physical Chemistry, Department of Chemistry Lund University (Sweden) [**] We thank the ETH Zürich, and the Swiss National Science Foundation (NRP 62 “Smart Materials” and SCOPES IZ73Z0- 128169) for financial support. Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/anie.201005164. 737 Angew. Chem. Int. Ed. 2011, 50, 737 –740  2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim