Porphyrin Urea-functionalized

Isocyanate and isothiocyanate precursors have been extensively used in the preparation of peptide analogues and other bioactive compounds. There are a few isolated examples of urea-functionalized porphyrins. No general method has been reported for the construction of urea-linked superstructured porphyrins. 

The twisted conformation inevitably adopted by meso-meso finked porphyrins has provided the basis for defined helical structures from dimeric and trimeric fcis-porphyrins 15 appropriately substituted with carboxylic acid functionalities, in the presence of an ancillary cyclic urea 16 [28]. The helical porphyrin arrays 17 that result in solution from complementary H-bonding exhibit chirality amplification and enhanced two-photon absorption properties. 

Additional saccharide receptors based on the picket-fence porphyrin were developed by the Bonar-Law group, but these were found to bind saccharides strongly only in nonpolar media. The starting material, the a,a,a,a-atropisomer of 5,10,15,20-me5O-tetrakis(o-aminophen-yl)porphyrin, 1 (cf. Figure 3), was functionalized with four different amino acid esters that were linked to the porphyrin scaffold by urea groups this yielded receptors 18a-d... 

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