Receptors tritopic

Subsequent to the preparation of 8, a number of other sapphyrin-nucleobase conjugated carriers were synthesized in the authors laboratories. These include compound 9 that has two cytosine moieties appended to the sapphyrin macrocycle, as well as two guanine-bearing sapphyrins, 10 and 11. Here, as expected, the ditopic sapphyrin-guanine receptor 10 served to enhance the transport of cytosine-5 -monophosphate (but not GMP or AMP). By contrast, the two tritopic receptors, namely 9 and 11, were designed with the intention of allowing for the formation of the complexation-derived triple-helix-like C-G-C and G-C-G motifs in addition to phosphate chelation by sapphyrin. In other words, it was expected that a centrally... 

Figure 3.3 Formation of a tritopic receptor in rosette form by self-assembly ...

In a different approach to carboxylate coniplexation, squaramide (i.e., 3,4-diamino-cyclobutene-1,2-dione) derivatives have been used by Prohens et al. as selective receptors (Fig. Ih). These receptors possess a parallel ditopic hydrogen bond donor array (c.f. urea) that show good to moderate association constants with acetate anions. A variety of mono-, di-. and tritopic receptors were synthesized, including the -squaramide receptor 19 that forms strong complexes with m-carboxylates such as trimesoate and cfs-cyclohexentricarboxylate (i a=3.9 X 1(PM and 7.7 x 10 M . respectively, in 10% DoO/DMSO.)... 

Balzani et al constructed a triply threaded, two-component oligo rotaxane R23, as seen in Figure 23. R23 contains two stations in each of its three arms. Threading of [Dum-R23H3] + into the tritopic receptor M-R23, in which three benzo[24]crown-8 macrorings are fused onto a triph-enylene core, yielded pseudorotaxane [M Dam-R23H3] +. The pseudorotaxane was then converted into rotaxane R23... 

---