View source for Erlenmeyer-Plöchl azlactone and amino acid synthesis

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==Overview==

The '''Erlenmeyer-Plochl azlactone and amino acid synthesis''', named after [[Friedrich Gustav Carl Emil Erlenmeyer]] who partly discovered the reaction, is a series of [[chemical reaction]]s which transform [[glycine]] to various other [[amino acid]]s via an [[oxazolone]] and an [[azlactone]].<ref>{{cite journal
 | author = Plöchl J.
 | title = Über einige Derivate der Benzoylimdozimtsäure
 | journal = [[Ber.]]
 | year = 1884
 | volume = 17
 | pages = 1623
 | url =http://gallica.bnf.fr/ark:/12148/bpt6k90700r/f39.chemindefer}}</ref><ref>{{cite journal
 | author = Erlenmeyer, F. 
 | title = Ueber die Condensation der Hippursäure mit Phtalsäureanhydrid und mit Benzaldehyd
 | journal = [[Ann.]]
 | year = 1893
 | volume = 275
 | pages = 3
 | doi =10.1002/jlac.18932750102}}</ref>

[[Image:AzlactoneChemistry.png|450px|center|Azlactone chemistry: step 2 is a Perkin variation]]

[[Hippuric acid]]<ref>{{OrgSynth | author = A. W. Ingersoll, S. H. Babcock | title = Hippuric acid | collvol = 2 | collvolpages = 328 | year = 1943 | prep = cv2p0328}}</ref> self-condenses in the presence of [[acetic anhydride]] to 2-phenyl-[[oxazolone]]<ref>{{OrgSynth | author = G. E. VandenBerg, J. B. Harrison, H. E. Carter, B. J. Magerlein |title = 2-Phenyl-2-oxazolone | collvol = 5 | collvolpages = 946 | year = 1973 | prep = CV5P0946}}</ref>. This intermediate also has two acidic protons and reacts with [[benzaldehyde]], acetic anhydride and sodium acetate to a so-called [[azlactone]]. This compound on reduction gives access to [[phenylalanine]].<ref>{{OrgSynth | author =  H. B. Gillespie, H. R. Snyder | title = dl-&beta;-Phenylalanine | collvol = 2 | collvolpages = 489 | year = 1943 | prep = CV2P0489}}</ref>

==Scope==
In one study the Erlenmeyer amino acid synthesis was used in the heart of an [[L-m-tyrosine]] synthesis <ref>''Optimized Synthesis of L-m-Tyrosine Suitable for Chemical Scale-Up'' Cara E. Humphrey, Markus Furegati, Kurt Laumen, Luigi La Vecchia, Thomas Leutert, J. Constanze D. Müller-Hartwieg, and Markus Vögtle Organic Process Research & Development '''2007''', 11, 1069–1075 {{DOI|10.1021/op700093y}}</ref> <ref>The [[benzyl ether]] of [[3-hydroxybenzaldehyde]] '''1''' reacts with the N-acetyl [[amide]] of [[glycine]] '''2''', [[acetic anhydride]] and [[sodium acetate]] to the azlactone (not displayed) which is ring-opened with sodium acetate in methanol to dehydroamino acid '''3'''. [[Hydrogenation]] gives the N-acyl-m-tyrosine methyl ester '''4''' (the benzyl ether group is also cleaved). This compound is [[racemic]] and [[kinetic resolution]] is brought about by an [[enzyme]] which is able to only cleave the methyl ester of the S-enantiomer (forming (S)-5 soluble in [[dichloromethane]]) leaving water soluble (R)-4 untouched. The final step is amide cleavage to (S)-L-m-tyrosine '''6''' </ref>

[[Image:ErlenMeyerAminoAcidSynthesisTyrosine.svg|600px|ErlenMeyer Amino Acid Synthesis Tyrosine]]

==References==
{{Reflist|2}}

==See also==
*[[Dakin-West reaction]]
*[[Perkin reaction]]

[[Category:Condensation reactions]]
[[Category:Heterocycle forming reactions]]


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