Hexahydroporphine is an

organic chemical compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon chemical bond, bonds. Due to carbon's ability to Catenation, catenate (form chains with other carbon atoms), millions of organic c ...

with formula . The molecule consists of four

pyrrole Pyrrole is a heterocyclic aromatic organic compound, a five-membered ring with the formula C4 H4 NH. It is a colorless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., ''N''-meth ...

rings connected by

methylene bridge In organic chemistry, a methylene bridge, methylene spacer, or methanediyl group is any part of a molecule with formula ; namely, a carbon atom bound to two hydrogen atoms and connected by single bonds to two other distinct atoms in the rest of ...

s into a larger (non-

aromatic In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...

)

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 car ...

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 chemical compound with formula . The molecule, which is flat, consists of four pyrrole-like rings joined by four methine (= C H−) groups to form a larger macrocycle ring, which makes it the simplest of the tetr ...

by the addition of six

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

atoms: four on the methine bridges, and two on the

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

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 Macrocycles are often described as molecules and ions containing a ring of twelve or more atoms. Classical examples in ...

s such as

uroporphyrinogen III Uroporphyrinogen III is a tetrapyrrole, the first 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 uroporphyri ...

(UROGEN), which are precursors of many

porphyrins Porphyrins ( ) are a group of heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (=CH−). The parent of porphyrin is porphine, a rare chemical compo ...

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

metabolic Metabolism (, from el, μεταβολή ''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 cell ...

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 or methylene chloride, methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odour 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 formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscib ...

, and

diethyl ether Diethyl ether, or simply ether, is an organic compound in the ether class with the formula , sometimes abbreviated as (see Pseudoelement symbols). It is a colourless, highly volatile, sweet-smelling ("ethereal odour"), extremely flammable liq ...

. 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