Porphyrins expanded

It should be noted here that expanded porphyrins, namely [22]porphyrin(4.0.4.0) and (22]porphyrin(6.0.6.0), have been prepared in Vogel s laboratory.1 1 The work on these porphyrins was only briefly reviewed in ref 1 e based on information from doctoral theses. Neither communications nor a full publication has appeared on this topic so the work is not reviewed here. 

The synthesis of homoporphyrins in which one methine bridge of the parent porphyrin is extended to a two-carbon bridge is one of the earliest and simplest examples of an expanded porphyrin.3a b>4 The synthesis of homoporphyrin 4 is based on the ability of N-alkylated porphyrin 1 to undergo nickel-induced rearrangement to form an expanded macrocycle 2. De-metalation of 2 by means of concentrated hydrochloric acid yields the cyclically conjugated [20]porphyrin(2.1.1.1) 4 and a macrocyclic side product 3 in which the cyclic conjugation is interrupted. 

The same porphyrin 20 is obtained when 3,4-diethylpyrrole-2,5-dicarbaldehyde is cyclized under McMurry conditions.8a,b Although the yield of this reaction is very low, the simplicity of this procedure and the possibility of optimizing the reaction conditions could open an attractive alternative route leading to this type of expanded porphyrins. 

In the previous sections, expanded porphyrins have been described in which the expansion is restricted to the pyrrole-linking bridges. The smallest expanded porphyrin in which the expansion is created by an additional pyrrole subunit in the macrocycle is the so-called orangarin, a [20]pentaphyrin(1.0.1.0.0).13 Orangarin 39 can be prepared via a hydrogen chloride induced... 

Sapphyrins were discovered serendipitously by Woodward33 during the course of synthetic studies directed towards the total synthesis of vitamin B, 2. The sapphyrins were the first example of expanded porphyrins in the literature. Due to sapphyrin exhibiting a deep-blue color in the crystalline state and intense green in solution. Woodward coined the expression sapphyrin with reference to the deep-blue color of sapphire stones. 

Chemical transformations at the macroeyclic chromophorc of expanded porphyrins are still not known. The complexation behavior of expanded porphyrins is very different from that of nonexpanded porphinoid macrocycles. The coordination hole of the expanded porphyrins is often too big for the complexation of a single metal ion, so in fact two metal ions can be chelated. With some expanded porphyrins, anion binding is observable, a striking difference to the nonexpanded porphyrins. The complexation behavior and the host-guest chemistry of expanded porphyrins is a rapidly growing field of research. The work in this field has been reviewed. Ie f... 

Sessler, J. L. Allen, W. E. Krai, V. A. Preparation of highly boronated derivatives of expanded porphyrins (texaphyrins) for potential use in boron neutron capture therapy and related applications. US Patent 5,955,586, 1999 Chem. Abstr. 1999, 131, 222611. 

The synthesis and biological evaluation of pyrrole macrocycles (i.e., porphyrins, expanded porphyrins, and calixpyrroles) and linear oligopyrroles comprise perhaps the largest body of work published each year that can be classified as pyrrole chemistry. Unfortunately, due to space limitations, the discussion of selected advances in this area could not be included. 

Texaphyrins (i.e. metal-coordinating expanded porphyrins, Fig. 27) have recently been investigated as new drugs for applications in radioimaging and PDT (140). 

Expanded porphyrins (sapphyrins) in their protonated forms can bind anions such as phosphate and nucleotides, but no electrochemical investigations have been reported to date (Sessler et al., 1991,1992). 

Seenisamy J, Bashyam S, Gokhale V, Vankayalapati H, Sun D, Siddiqui-Jain A, Streiner N, Shin-Ya K, White E, Wilson WD, Hurley EH (2005) Design and synthesis of an expanded porphyrin that has selectivity for the c-MYC G-quadruplex structure. J Am Chem Soc 127(9) 2944-2959 Sen D, Crothers DM (1986) Influence of DNA-binding drugs on chromatin condensation. Biochemistry 25(7) 1503-1509... 

Seel C, Galdn A, de Mendoza J (1995) Molecular Recognition of Organic Acids and Anions -Receptor Models for Carboxylates, Amino Acids, and Nucleotides. 175 101 -132 Sendhoff N,see KnopsP(1991) 161 1-36 Sessler JL, Burrell AK (1991) Expanded Porphyrins. 161 177-274... 

Sapphyrin (e.g., 2) is the most venerable of the many expanded porphyrins now known. It was first discovered serendipitously in the Woodward group more than 30 years ago during the course of studies directed toward the synthesis of vitamin Recently improved syntheses of sapphyrin have been developed by the... 

For examples of expanded porphyrin-derived chloride receptors (other than sapphyrin), see Sessler, J.L. Morishima,T. Lynch, V. Angew. Chem. Int. Ed. Engi 1991, JO, 977, and refs. 12-14. 

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