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Isoquinoline, also known as benzo[c]pyridine or 2-benzanine, is a heterocyclic aromatic organic compound. It is a structural isomer of quinoline. Isoquinoline and quinoline are benzopyridines, which are composed of a benzene ring fused to a pyridine ring. In a broader sense, the term isoquinoline is used to make reference to isoquinoline derivatives. Isoquinoline is the structural backbone in naturally occurring alkaloids including papaverine and morphine. The isoquinoline ring in these natural compound derives from the aromatic amino acid tyrosine.
Isoquinoline is a colorless hygroscopic liquid at room temperature with a penetrating, unpleasant odor. Impure samples can appear brownish, as is typical for nitrogen heterocycles. It crystallizes platelets that have a low solubility in water but dissolve well in ethanol, acetone, diethyl ether, carbon disulfide, and other common organic solvents. It is also soluble in dilute acids as the protonated derivative.
Isoquinolone was first isolated from coal tar in 1885 by Hoogewerf and van Dorp. They isolated it by fractional crystallization of the acid sulfate. Weissgerber developed a more rapid route in 1914 by selective extraction of coal tar, exploiting the fact that isoquinoline is more basic than quinoline. Isoquinoline can then be isolated from the mixture by fractional crystallization of the acid sulphate.
Although isoquinoline derivatives can be synthesized by several methods, relatively few direct methods deliver the unsubstituted isoquinoline. The Pomeranz-Fritsch reaction provides an efficient method for the preparation of isoquinoline:
The following methods are useful for the preparation of various isoquinoline derivatives:
Applications of derivatives
Isoquinolines find many applicatons, including (but not limited to):
Isoquinolines and the human body
Parkinson's disease, a slowly progressing movement disorder, is thought to be caused by certain neurotoxins. A neurotoxin called MPTP (1[N]-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), the precursor to MPP+, was found and linked to Parkinson's disease in the 1980's. The active neurotoxins destroy dopaminergic neurons, leading to parkinsonism and Parkinson's disease. Several tetrahydroisoquinoline derivatives have been found to have the same neurochemical properties as MPTP. These derivatives may act as neurotoxin precursors to active neurotoxins.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Isoquinoline". A list of authors is available in Wikipedia.|