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Synthesis of Highly Substituted Cryptophane Derivatives

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posted on 21.06.2013 by Thierry Brotin, Dominique Cavagnat, Erwann Jeanneau, Thierry Buffeteau
We report the synthesis of new cryptophane derivatives 14 bearing nine (1, 2) and twelve (3, 4) methoxy substituents. These compounds represent the first examples of cryptophane derivatives bearing more than six substituents attached on the benzene rings. The preparation of these highly substituted cryptophanes was achieved due to the synthesis of a new cyclo­trisyringyl derivative obtained from the reaction of a protected syringyl alcohol in the presence of a catalytic amount of scandium triflate Sc­(OTf)3. This reaction also provides the protected cyclotetra­syringyl derivative in low yield (7%), which was fully characterized by 1H NMR, IR, and X-ray crystallography. In contrast to what is observed for the crypto­phane-A congener, the synthesis of these highly substituted cryptophanes gives rise to the two anti- and syn-diastereomers. These compounds have been fully characterized, and their X-ray structures have been obtained to ascertain the stereochemistry of these new cryptophane derivatives.