Sapphyrin conjugate

Figure 16. Cytosine-sapphyrin conjugate attached to silica gel.

So far, several different kinds of sapphyrin conjugates have appeared in the literature. The first of these to be reported were the sapphyrin-cytosine conjugates 5.112 and 5.1 These were prepared by reacting l-(2-aminoethyl)-4-... 

The approach makes use of a bipyrroledicarbaldehyde 54 and a tripyrranedicarboxylic acid 55 which are condensed with subsequent decarboxylation in the presence of acid and oxygen. The presence of oxygen, as in many other syntheses of porphinoid macrocycles, is necessary to adjust the oxidation level of the chromophore which is in sapphyrins a 2271-aromatic cyclically conjugated system. Many sapphyrins 56 with different substitution patterns have been synthesized according to this general scheme. As in all McDonald-type condensations at least one of the components has to be symmetric because otherwise mixtures of constitutional isomers would be formed. 

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... 

While many sapphyrin-derived conjugates can be conceived that would allow one to study more extensively the interactions of this fascinating chromophore/an-ion binding agent with DNA, most of these remain as yet unprepared at present. 

One critical exception is the sapphyrin-ethylenediaminetetraacetic (EDTA) conjugate (23). Previous studies of small molecule-EDTA conjugates have shown that these species, in the presence of iron(II), Oj, and a suitable reducing agent, can effect the cleavage of the DNA backbone. In turn, so-called affinity cleavage can be used to elucidate the specificity of the small molecule-DNA interactions. It was thus considered worth making 23. ... 

Krai, V., Sessler, J. L., Furuta, H., Synthetic sapphyrin cytosine conjugates - carriers for selective nucleotide transport at neutral Ph. J. Am. Chem. Soc. 1992, 114, 8704-8705. 

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