Amino acid ''N''-carboxyanhydrides, also called Leuchs' anhydrides, are a family of
heterocyclic
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...
s derived from
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...
s. They are white, moisture-reactive solids. They have been evaluated for applications the field of
biomaterials
A biomaterial is a substance that has been engineered to interact with biological systems for a medical purpose, either a therapeutic (treat, augment, repair, or replace a tissue function of the body) or a diagnostic one. As a science, biomateria ...
.
Preparation
140px, Glycine N-carboxyanhydride is the parent member of the amino acid N-carboxyanhydrides.
NCAs are typically prepared by
phosgenation
Phosgene is the organic chemical compound with the formula COCl2. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. Phosgene is a valued and important industrial building block, es ...
of
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...
s:
They were first synthesized by
Hermann Leuchs
Friedrich Hermann Leuchs (8 August 1879 – 2 May 1945) was a German chemist.
Life
Leuchs studied chemistry at the University of Munich from 1898. He transferred to the University of Berlin and received his Ph.D. there in 1902 under Emil Fischer ...
by heating an ''N''-ethoxycarbonyl or ''N''-methoxycarbonyl
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...
chloride in a vacuum at 50-70 °C:
A moisture-tolerant route to unprotected NCAs employs
epoxide
In organic chemistry, an epoxide is a cyclic ether () with a three-atom ring. This ring approximates an equilateral triangle, which makes it strained, and hence highly reactive, more so than other ethers. They are produced on a large scale ...
s as scavengers of hydrogen chloride.
[
This synthesis of NCAs is sometimes called the . The relatively high temperatures necessary for this cyclization results in the decomposition of several NCAs. Of several improvements, one notable procedure involves treating an unprotected amino acid with ]phosgene
Phosgene is the organic chemical compound with the formula COCl2. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. Phosgene is a valued and important industrial building block, es ...
or its trimer.
Reactions
NCAs are prone to hydrolysis to the parent amino acid:
:RCHNHC(O)OC(O) + H2O → H2NCH(R)CO2H + CO2
Some derivatives however tolerate water briefly.Peptide synthesis
In organic chemistry, peptide synthesis is the production of peptides, compounds where multiple amino acids are linked via amide bonds, also known as peptide bonds. Peptides are chemically synthesized by the condensation reaction of the carboxy ...
from NCAs does not require protection of the amino acid functional group
In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the res ...
s. N-Substituted NCAs, such as sulfenamide derivatives have also been examined.catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
s.
Further reading
*
*
*
*
See also
* Dakin–West reaction
* Glycine N-carboxyanhydride, the parent NCA
References
{{Reflist
Organic chemistry
Organic reactions
