Enantioselective Synthesis of Amino Acids

E. Juaristi, Enantioselective Synthesis of Amino Acids. Wiley-VCH, New York, 1997. 

A regio-, diastereo- and enantioselective synthesis of amino acids was reported by Takemoto and coworkers. The glycine equivalent ethyl diphenylimino glycinate was used as pronucleophile (Scheme 9.14), while the Hgand was a bidentate chiral phosphite, and 3-arylaUyl diethyl phosphates were employed as allylic substrates [39, 46]. 

W. Bettray, J. Schankat, J. Wiedemann, in Enantioselective Synthesis of -Amino Acids (Ed. E. Juaristi), Wiley-VCH, New York 1997, p. 187. 

Elaridi, J., Thaqi, A., Prosser, A., Jackson, W.R. and Rohinson, A.J. An Enantioselective Synthesis of -Amino Acid Derivatives. Tetrahedron Asymmetry 2005, 16, 1309-1319. 

Gutierrez-Garcia, V. M. Lopez-Ruiz, H. Reyes-Rangel, G. Juaristi, E. Enantioselective synthesis of / -amino acids. Part 11. Diastereo-selective alkylation of chiral derivatives of /J-aminopropionic acid containing the jS-phenethyl group. Tetrahedron 2001, 57, 6487-6496. 

Asymmetric Catalytic Aminoalkylations New Powerful Methods for the Enantioselective Synthesis of Amino Acid Derivatives, Mannich Bases, and Homoallylic Amines... 

Juaristi E (ed) (1997) Enantioselective synthesis of -amino acids. Wiley, New York... 

Akiyama T, Saitoh Y, Morita H, Fuchibe K (2005b) Adv Synth Catal 347 1523 Akiyama T, Tamura Y, Itoh J, Morita H, Fuchibe K (2006a) Synlett 2006 141 Arend M (1999) Asymmetric catalytic aminoalkylations new powerful methods for the enantioselective synthesis of amino acid derivatives, Mannich bases, and homoallylic amines. Angew Chem Int Ed Engl 38 2873-2874 Arend M, Westermann B, Risch N (1998) Angew Chem Int Ed Engl 37 1045 Avemaria F, Vanderheiden S, Brase S (2003) Tetrahedron 59 6785 Babu G, Perumal PT (1998) Tetrahedron 54 1627... 

Konopelski, J. P. In Enantioselective Synthesis of -Amino Acids, Juaristi, E., Ed. Wiley New York, 1997, pp 249-259,... 

Modern reactions While there is no shortage of new chemical reactions to present in an organic chemistry test, I have chosen to concentrate on new methods that introduce a particular three-dimensional arrangement in a molecule, so-called asymmetric or enanti-oselective reactions. Examples include Sharpless epoxidation (Chapter 12), CBS reduction (Chapter 20), and enantioselective synthesis of amino acids (Chapter 28). 

Sheehan, S. M. Preline-catalyzed asymmetric Mannich reactions The highly enantioselective synthesis of amino acid derivatives and 1,2-amino alcohols. Chemtracts 2002, 15, 384-390. 

An enantioselective synthesis of amino acids has been examined using chiral nonracemic a-imino esters (36) derived from (S)-l-phenylethylamine and (-)-l-cyclohexylethylamine (equation 9, Table 9). Allyl-magnesium, -copper and -titanium reagents react at both the imine and ester carbon atoms of (36), a result of the molecule s ambient electrophilicity. The addition of allyl-, methallyl- and prenyl-9-BBN and -ZnBr to a-imino ester (36), however, generates amines (38) and (39). While the absolute stereochemistry of (38) and (39 R = Ph) has been determined (entries 1-4, Table 9), that of the cyclohexyl-ethylamine-derived products has not (entries 5-8, Table 9). 

Enzymatic methods offer in principle the possibility of a direct enantioselective synthesis of amino acids. Enzymes are often used for separation of racemic mixtures, as examplified in the case of methionine. Although racemic methionine is adequate for the animal feed sector, other applications require the enan-tiomerically pure (L)-form. For the resolution, (L)-acylases from Aspergillus sp. are often used, since they can accept a broad spectrum of substrates, are highly active, and very stable under the production conditions. [62]... 

The classic example of enantioselective synthesis of amino acids concerns the enantioselective hydrogenation of an aminocinnamic acid derivative for the preparation of the unnatural amino acid (L)-3,4-dihydroxyphenylalanine (L-DOPA). This is a very convincing and instructive case, because for the first time a particularly high enantiomeric excess was achieved, and here some fundamental aspects of enantioselective catalysis can be demonstrated. 

Figure 3 Enantioselective synthesis of amino acids with the help of an MIP, prepared by covalent imprinting.

Wulff, G. Vietmeier, J. Enz me-analog built polymers. 26. Enantioselective synthesis of amino acids using pol5mers possessing chiral cavities obtained by an imprinting procedure with template molecules. Makromol. Chem. 1989,190, 1727-1735. 

Progress in the enantioselective synthesis of amino acids has been made, most notably this year by Seebach s research group. Simple amino acids, such as (S)-alanine, are converted into cis-(29) and trans-(29) imidazolidinones. These heterocycles undergo deprotonation to afford chiral enolates, alkylation of which takes... 

Amino acids can be synthesized in racemic form by several methods, including alkylation of diethyl acetamidomalonate and reductive amination of an a-keto acid. Alternatively, an enantioselective synthesis of amino acids can be carried out using a chiral hydrogenation catalyst. 

Enantioselective synthesis of amino acids may be achieved by modification of the Strecker synthesis with a chiral additive or hydrogenation of dehydroamino acid derivative (prepared via an aziactone synthesis) in the presence of a metal complex of a chiral phosphine. 

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