Steroid-functionalized porphyrin

Figure 25 Schematic rendition of the mode of binding of the steroid-functionalized porphyrin (28) and the possible interaction with a steroid substrate at the site of oxidation, as suggested by Groves and Neumann [91]...

Pantothenic acid has a central role in energy-yielding metabolism as the functional moiety of coenzyme A (CoA), in the biosynthesis of fatty acids as the prosthetic group of acyl carrier protein, and through its role in CoA in the mitochondrial elongation of fatty acids the biosynthesis of steroids, porphyrins, and acetylcholine and other acyl transfer reactions, including postsynthetic acylation of proteins. Perhaps 4% of all known enzymes utilize CoA derivatives. CoA is also bound by disulfide links to protein cysteine residues in sporulating bacteria, where it may be involved with heat resistance of the spores, and in mitochondrial proteins, where it seems to be involved in the assembly of active cytochrome c oxidase and ATP synthetase complexes. 

The metabolic functions of pantothenic acid in human biochemistry are mediated through the synthesis of CoA. Pantothenic acid is a structural component of CoA. which is necessary for many important metabolic processes. Pantothenic acid is incorporated into CoA by a. series of five enzyme-catalyzed reactions. CoA is involved in the activation of fatty acids before oxidation, which requires ATP to form the respective fatty ocyl-CoA derivatives. Pantothenic acid aI.so participates in fatty acid oxidation in the final step, forming acetyl-CoA. Acetyl-CoA is also formed from pyruvate decarboxylation, in which CoA participates with thiamine pyrophosphate and lipoic acid, two other important coenzymes. Thiamine pyrophosphate is the actual decarboxylating coenzyme that functions with lipoic acid to form acetyidihydrolipoic acid from pyruvate decarboxylation. CoA then accepts the acetyl group from acetyidihydrolipoic acid to form acetyl-CoA. Acetyl-CoA is an acetyl donor in many processes and is the precursor in important biosyntheses (e.g.. those of fatty acids, steroids, porphyrins, and acetylcholine). 

A member of the vitamin-B complex it is a component of coenzyme A and may be considered a (3-alanine derivative with a peptide linkage. It is involved in the release of energy from carbohydrate utilization and is necessary for synthesis and degradation of fatty acids, sterols, and steroid hormones it also functions in the formation of porphyrins. It occurs in all living cells and tissues. The natural product is dextrorotatory [d(+)] and is the only form having vitamin activity. 

Regioselectively addressable functionalized templates (RAFT), oligovalent moieties with chemically distinct functional groups that can be selectively addressed in the preparation of template-associated synthetic proteins (TASP). RAFT are molecular scaffolds that comprise porphyrins, steroids, calixarenes, glycosides, and a variety of cyclic peptides and peptidomimetics. RAFT... 

Guanidium-Based Anion Receptors, p. 615 Hydrogen Bonding, p. 658 Hydrophobic Effects, p. 673 Molecular Clefts and Tweezers, p. 887 Porphyrin Derivatives, Functional, p. 1139 Steroid-Based Anion Complexation Agents, p. 1365 Troeger s Base Derivatives, p. 15 6 Zwitterion Receptors, p. 1639... 

Sophisticated supramolecular catalysts, based on CDs, appended to a Mn porphyrin active site were synthesized in order to preorganize a substrate next to an active site. In particular, a steroid substrate was functionalized at both ends with tert-butylphenyl groups (Gi in Figure 12) that were able to interact with the CD cavities. Hydroxylation... 

Figure 12 Regioselective hydroxylation of a functionalized steroid with a Mn porphyrin catalyst bearing four cyclodextrin receptors. The same reaction carried out with a different functionalized steroid leads to a mixture of products. ...

The electrochemical oxidation of 17p-estradiol—a steroid that causes abnormal thyroid function in birds and fish—was obtained with copper meso-tetra(thien-2-yl)porphyrin/RGO hybrid [126]. 

Granick, S., and Kappas, A. (1967). Steroid control of porphyrin and heme biosynthesis A new biological function of steroid hormone metabolites. Proc. Natl. Acad. Sci. U.S. 57, 1463-1467. 

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