Corrin
Encyclopedia
Corrin is an heterocyclic compound
. It is the parent macrocycle
related to substituted
derivative that is found in vitamin B12
. Its name reflects that it is the "core" of vitamin B12
(cobalamins).
. In vitamin B12, the resulting complex also features a benzimidazole-derived ligand, and the sixth site on the octahedron serves as the catalytic center.
The corrin ring resembles the porphyrin
ring, which occurs in hemoglobin
. Both feature four pyrrole
-like subunits organized into a ring. In contrast to porphyrin
s, corrins lack one of the carbon groups that link the pyrrole-like units. Thus the large ring has 15 atoms, whereas porphyrins have 16. Also, the pyrrole-like rings in corrin are fully saturated "edge-carbon" centers. Because of the high number of sp3 carbon centers, corrins are more flexible than porphyrins and are not as flat. They do not have a full conjugated
character around the entire ring. Instead, the ring has a kind of "3/4" conjugation.
Corrole
s (octadehydrocorrins) are fully aromatic derivatives of corrins.
Heterocyclic compound
A heterocyclic compound is a cyclic compound which has atoms of at least two different elements as members of its ring. The counterparts of heterocyclic compounds are homocyclic compounds, the rings of which are made of a single element....
. It is the parent macrocycle
Macrocycle
A macrocycle is, as defined by IUPAC, "a cyclic macromolecule or a macromolecular cyclic portion of a molecule." In the chemical literature, organic chemists may consider any molecule containing a ring of nine or more atoms to be a macrocycle...
related to substituted
Substituent
In organic chemistry and biochemistry, a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon...
derivative that is found in vitamin B12
Vitamin B12
Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
. Its name reflects that it is the "core" of vitamin B12
Vitamin B12
Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
(cobalamins).
Coordination chemistry
Upon deprotonation, the corrinoid ring is capable of binding cobaltCobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
. In vitamin B12, the resulting complex also features a benzimidazole-derived ligand, and the sixth site on the octahedron serves as the catalytic center.
The corrin ring resembles the porphyrin
Porphyrin
Porphyrins are a group of organic compounds, many naturally occurring. One of the best-known porphyrins is heme, the pigment in red blood cells; heme is a cofactor of the protein hemoglobin. Porphyrins are heterocyclic macrocycles composed of four modified pyrrole subunits interconnected at...
ring, which occurs in hemoglobin
Hemoglobin
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
. Both feature four pyrrole
Pyrrole
Pyrrole is a heterocyclic aromatic organic compound, a five-membered ring with the formula C4H4NH. It is a colourless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., N-methylpyrrole, C4H4NCH3...
-like subunits organized into a ring. In contrast to porphyrin
Porphyrin
Porphyrins are a group of organic compounds, many naturally occurring. One of the best-known porphyrins is heme, the pigment in red blood cells; heme is a cofactor of the protein hemoglobin. Porphyrins are heterocyclic macrocycles composed of four modified pyrrole subunits interconnected at...
s, corrins lack one of the carbon groups that link the pyrrole-like units. Thus the large ring has 15 atoms, whereas porphyrins have 16. Also, the pyrrole-like rings in corrin are fully saturated "edge-carbon" centers. Because of the high number of sp3 carbon centers, corrins are more flexible than porphyrins and are not as flat. They do not have a full conjugated
Conjugated system
In chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in compounds with alternating single and multiple bonds, which in general may lower the overall energy of the molecule and increase stability. Lone pairs, radicals or carbenium ions may be part of the...
character around the entire ring. Instead, the ring has a kind of "3/4" conjugation.
Corrole
Corrole
A corrole is an aromatic organic chemical, whose structure is in the form of the corrin ring which is also present in cobalamin . The ring consists of nineteen carbon atoms, with four nitrogen atoms in the core of the molecule....
s (octadehydrocorrins) are fully aromatic derivatives of corrins.