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Application of Asymmetric Catalysis to the Synthesis of Peptide Mimics
Published in John R. Kosak, Thomas A. Johnson, Catalysis of Organic Reactions, 2020
John J. Talley, Cathleen E. Hanau, Gary A. DeCrescenzo, Michelle A. Schmidt
The report by Christopf el and Vineyard [1] on the preparation of certain esters of 2(R)-methylsuccinic acid from the corresponding itaconic acid esters provided the groundwork for our work on the asymmetric synthesis of 2-substituted succinic acids [2] (Eq. 1). Asymmetric hydrogenation of monomethyl itaconate (1) in the presence of rhodium (R,R) DiPAMP [3] produced 2 in excellent yield with a high degree of asymmetric induction, ca. 90% ee. Interestingly, the degree of asymmetric induction and the absolute configuration of the hydrogenation shown in Eq. 1 was the same as that reported for the reduction of acyldehydroalanine derivative 3 (Eq. 2). Since substitution of the β-olefinic carbon of 3 does not significantly alter the enantioselectivity of this reduction, we reasoned that a variety of chiral 2-substituted succinic acid derivatives would be accessible from the appropriately functionalized alkylidene succinate, 5 (R ≠ H).
Palladium-Catalyzed Coupling of Aryl Halides and Aryl Triflates to Itaconate Diesters: A Convenient Preparation of E-Benzylidenesuccinate Diesters
Published in Mike G. Scaros, Michael L. Prunier, Catalysis of Organic Reactions, 2017
Michelle A. Schmidt, John J. Talley, Mike G. Scaros, Peter K. Yonan
We had previously observed that catalytic asymmetric hydrogenation of benzylidenesuccinates, (1), in the presence of rhodium (R, R)DiPAMP5b provided chiral (R)-benzylsuccinates5c with a high degree of optical purity, see Eq. 1. While the Stobbe condensation of aliphatic aldehydes with dialkyl succinates, Eq. 2, generally provides the corresponding 2-alkylidenesuccinates in acceptable yield6, we found this condensation to be generally poorer when aromatic aldehydes were used. The Heck arylation reaction, Eq. 3, however, provided arylidenesuccinates in good to excellent yields in most instances. We report herein an investigation of palladium catalyzed coupling of itaconate diesters with a variety of aryl halides and aryl triflates.
Transition metal-catalyzed hydrogenation
Published in Ilya D. Gridnev, Pavel A. Dub, Enantioselection in Asymmetric Catalysis, 2016
The conformation of the chelate cycle of the catalyst in solution must be determined in the Rh complexes of the ligands 142–146 by the substituents on phosphorus. The substituted phenyls would therefore preferentially occupy the equatorial positions. This is confirmed by the X-ray structure for the rhodium complex of 146 (Figure 1.20).42 In solution, the tetrahydronaphthalene substituents can easily acquire a conformation where they would not create any hindrance above the chelate cycle, whereas the axial positions of the phenyls would be fixed by the conformational locks (Figure 1.20b). Accepting this line of argument, it can be concluded that the unsubstituted phenyls in the Rh complex of 146 act as stereoregulating substituents. This, in turn, gives a quadrant diagram that coincides with the general quadrant rule (see above). In other words, being formally P-stereogenic ligands, DIPAMP (142) and its analogs (143–146) work as the catalysts with backbone chirality in asymmetric hydrogenation (Figure 1.20).
Metabolic engineering of Escherichia coli W3110 strain by incorporating genome-level modifications and synthetic plasmid modules to enhance L-Dopa production from glycerol
Published in Preparative Biochemistry and Biotechnology, 2018
Arunangshu Das, Neetu Tyagi, Anita Verma, Sarfaraz Akhtar, Krishna J. Mukherjee
Fifty years after the introduction of L-Dopa by George Cotzias as the successful proven treatment of Parkinson's disease and dopamine-responsive dystonia it still remains the only standalone drug available in the market.[1] The current L-Dopa industry turnover is around 250 tons per year with a market value of 101 million per year.[2] The bulk of L-Dopa produced by different industries worldwide comes from catalytic asymmetric hydrogenation of cinnamic acid which employs [Rh(R,R)–DiPAMP)COD]+BF4– catalyst and is known as Monsanto process. The major drawbacks of the process are poor yield and lack of enantioselectivity.[3] Nevertheless, catalytic asymmetric synthesis of L-Dopa is going to be backbone of industry for quite a while from now as the alternatives will take time to emerge as viable industrial technologies in future. Pathway engineering and simultaneous bio-process optimization which has proven to be highly successful for many other commercial metabolites such as tyrosine, phenylalanine, tryptophan, and shikimic acid is a viable alternative which can replace the tedious chemical synthesis of L-Dopa in future.