Hexahydroporphine is an

organic chemical compound Some chemical authorities define an organic compound as a chemical compound that contains a Carbon–hydrogen bond, carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. F ...

with formula . The molecule consists of four

pyrrole Pyrrole is a heterocyclic, aromatic, organic compound, a five-membered ring with the formula . It is a colorless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., ''N''-methylpyrrol ...

rings connected by

methylene bridge In chemistry, a methylene bridge is part of a molecule with formula . The carbon atom is connected by single bonds to two other distinct atoms in the rest of the molecule. A methylene bridge is often called a methylene group or simply methylene, ...

s into a larger (non-

aromatic In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...

)

macrocycle Macrocycles are often described as molecules and ions containing a ring of twelve or more atoms. Classical examples include the crown ethers, calixarenes, porphyrins, and cyclodextrins. Macrocycles describe a large, mature area of chemistry. ...

ring, which makes it one of the simplest

tetrapyrrole Tetrapyrroles are a class of chemical compounds that contain four pyrrole or pyrrole-like rings. The pyrrole/pyrrole derivatives are linked by ( or units), in either a linear or a cyclic fashion. Pyrroles are a five-atom ring with four carbon ...

s, and the simplest "true" one. As indicated by the name, it may be viewed as derived from

porphine Porphine or porphin is an organic compound of empirical formula . It is heterocyclic and aromatic. The molecule is a flat macrocycle, consisting of four pyrrole-like rings joined by four methine bridges, which makes it the simplest of the tetrap ...

by the addition of six

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

atoms: four on the

methine bridge In organic chemistry, a methine group or methine bridge is a trivalent functional group , derived formally from methane. It consists of a carbon atom bound by two single bonds and one double bond, where one of the single bonds is to a hydrogen. T ...

s, and two on the

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

atoms. Hexahydroporphine does not occur in nature, but is the core of

porphyrinogen In biochemistry, a porphyrinogen is a member of a class of naturally occurring compounds with a tetrapyrrole core, a macrocycle of four pyrrole rings connected by four methylene bridges.

s such as

uroporphyrinogen III Uroporphyrinogen III is a tetrapyrrole, the first macrocycle, macrocyclic intermediate in the biosynthesis of heme, chlorophyll, vitamin B12, and siroheme. It is a colorless compound, like other porphyrinogens. Structure The molecular structure of ...

(UROGEN), which are precursors of many

porphyrins Porphyrins ( ) are heterocyclic, macrocyclic, organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (). In vertebrates, an essential member of the porphyrin group is heme, whi ...

— derivatives of porphine of great biological importance. The six hydrogens of that core are removed at a later

metabolic Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the ...

stage by the enzyme

protoporphyrinogen oxidase Protoporphyrinogen oxidase or protox is an enzyme that in humans is encoded by the ''PPOX'' gene. Protoporphyrinogen oxidase is responsible for the seventh step in biosynthesis of protoporphyrin IX. This porphyrin is the precursor to hemoglobin, ...

. Because of this connection, the compound is also called (unsubstituted) porphyrinogen. The compound is a colorless solid, soluble in

dichloromethane Dichloromethane (DCM, methylene chloride, or methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odor is widely used as a solvent. Although it is not miscible with ...

acetone Acetone (2-propanone or dimethyl ketone) is an organic compound with the chemical formula, formula . It is the simplest and smallest ketone (). It is a colorless, highly Volatile organic compound, volatile, and flammable liquid with a charact ...

, and

diethyl ether Diethyl ether, or simply ether, is an organic compound with the chemical formula , sometimes abbreviated as . It is a colourless, highly Volatility (chemistry), volatile, sweet-smelling ("ethereal odour"), extremely flammable liquid. It belongs ...

. It decomposes at 185°C.

Preparation

Derivatives of hexahydroporphine, with various groups attached to the pyrrole or methylene bridges, occur in nature and have been studied for a long time.P. S. Clezy and C. J. R. Fookes (1977): "The chemistry of pyrrolic compounds. XXXVIII. The synthesis of hexahydroporphyrin a and related compounds". ''Australian Journal of Chemistry'', volume 30, issue 8, pages 1799–1813. A. H. Jackson (2009): "The total synthesis of pyrrole pigments". In John ApSimon (ed.), ''The Total Synthesis of Natural Products'', volume 1; Wiley, 624 pages. Goutam K. Lahiri and Alan M. Stolzenberg(1993): "Facile Formation of Hexahydroporphyrin Complexes by Reduction of Octaethylisobacteriochlorinnickel(II)". ''Angewandte Chemie'', volume 32, issue 3, pages 429-432. Hidemitsu Uno, Takashi Inoue, Yumiko Fumoto, Motoo Shiro, and Noboru Onomeso (2000): "Unsubstituted Porphyrinogens and Hexaphyrinogens: The First X-ray Characterization" ''Journal of the American Chemical Society'', volume 122, issue 28, pages 6773–6774. The unsubstituted compound, however, has been synthesized in good yield only in 2001. It can be obtained by successive condensations of 2,5-bis(hydroxymethyl)pyrrole and pyrrole, with a tripyrrole intermediate.Shozo Taniguchi, Hikaru Hasegawa, Shoko Yanagiya, Yusuke Tabeta, Yoshiharu Nakano, and Masahiko Takahashi (2001): "The first isolation of unsubstituted porphyrinogen and unsubstituted 21-oxaporphyrinogen by the ‘3+1’ approach from 2,5-bis(hydroxymethyl)pyrrole and tripyrrane derivatives". ''Tetrahedron'', volume 57, issue 11, pages 2103-2108. The compound can also be prepared by reduction of porphin-zinc complexes.Gilbert R. Seely and Melvin Calvin (1955): "Photochemical Studies of the Porphyrins. III. Photoreduction of a Porphyrin by Benzoin" ''Journal of Chemical Physics'', volume 23, issue 6, pages 1068–. Gilbert R. Seely (1957): "Molecular Orbital Study of the Porphyrins". ''Journal of Chemical Physics'', volume 27, issue 1, pages 125–.

References

{{reflist Tetrapyrroles

Preparation

See also

References