Strecker catalytic asymmetric

Moreover, it seemed to be a rational extension to apply the catalyst 123 to the asymmetric Strecker-type reaction.1291 Actually, as shown in Table 13, an efficient and general catalytic asymmetric Strecker-type reaction has been realized. Products were successfully converted to the corresponding amino acid derivatives in high yields without loss of enantiomeric purity.1301... 

Shibasaki, A Catalytic Asymmetric Strecker-type Reaction Interesting Reactivity Difference between TMSCN and HCN, Angew. Chem Int. Ed. Engl. 2000,39,1650-1652... 

Matsumoto, K. Kim, J. C. Hayasbi, N. Jenner, G. Tetrahedron Lett. 2002, 43, 9167. Yet, L. Recent Developments in Catalytic Asymmetric Strecker-Type Reactions, in Organic Synthesis Highlights V, Scbmalz, H.-G. Wirtb, T. eds., Wiley-VCH Weinbeim, Germany, 2003, pp 187-193. (Review). 

Representative metal complexes employed for the catalytic asymmetric Strecker reaction are summarized in Figure 4.2. Aluminum-, titanium-, lanthanoid-, and zirconium-based catalysts are highly efficient. Direct one-pot synthesis starting from aldehydes, and amines is reported using the Zr complex described in Figure 4.2. ... 

One of the most important approaches to a-amino acids is based on the Strecker reaction. Although there are already a number of catalytic asymmetric variants, the cyanation of imines still challenges modem organic chemists. 

Yet L (2001) Recent developments in catalytic asymmetric Strecker-type reactions. Angew Chem Int Edit 40(5) 875-877... 

The wide assortment of catalytic asymmetric Strecker reaction methodologies devised to date can be divided into two major categories based on the nature of catalyst utilized 1) Lewis acid-promoted and 2) metal-free (or organo-catalytic) systems. Both classes of catalysis will be discussed and key results will be highlighted. 

Table 1. Overview of the methods for the catalytic asymmetric Strecker reaction... 

Catalytic Asymmetric Strecker Synthesis of Amino Acids. 172... 

The bifunctional mechanism proposed for the Ti-catalyzed Strecker suggests that electrophiles other than amines can be induced to undergo catalytic asymmetric additions with cyanide. The details of the optimal conditions (exactly what ligand structure, metal salt, solvent, and any needed additives) would however have to be identified through screening of parallel libraries as mentioned above. In this fashion, we have been able to develop an Al-catalyzed asymmetric... 

A large number of catalytic asymmetric MCR are based on deoxo-bisubstitution reactions of carbonyl compounds such as the Mannich and Strecker reactions in which an oxo-group is displaced by two new cr-bonds, one to a nitrogen atom and one to a carbon atom. Other examples of deoxo-bisubstitutions include tandem processes that involve an initial Knoevenagel condensation followed by either a nucleophilic or a cycloaddition. These processes are characterized by the conversion of a C O-K-bond into two new C-C-cr-bonds and have been termed carba-acetalizations. 

The first catalytic asymmetric Strecker reaction was reported by the Upton group using the cyclic dipeptide 5 as an organocatalyst [4, 5, 15]. This diketopiperazine 5 was prepared starting from (S)-phenylalanine and (S)-a-amino-y-guanidinobutyric... 

Recent Developments in Catalytic Asymmetric Strecker-Type Reactions... 

The Strecker amino acid synthesis, which involves treatment of aldehydes with ammonia and hydrogen cyanide (or equivalents) followed by hydrolysis of the intermediate a-amino nitriles to provide a-amino acids (Scheme 1), was first reported in 1850 [1], This method has been applied on an industrial scale toward the synthesis of racemic a-amino acids, but more recently interest in nonproteinogenic a-amino acids in a variety of scientific disciplines has prompted intense activity in the asymmetric syntheses of a-amino acids [2]. The catalytic asymmetric Strecker-type reaction offers one of the most direct and viable methods for the asymmetric synthesis of a-amino acid derivatives. It is the purpose of this Highlight to disclose recent developments in this emerging field of importance. 

Shibasaki and co-workers disclosed a general asymmetric Strecker-type reaction that was controlled by bifunctional Lewis acid-Lewis base catalyst 14 [10], N-Fluorenylimines 15 underwent catalytic asymmetric Strecker-type reactions with binaphthol catalyst 14 to give a-aminonitriles 16 in good to excellent enantioselectivities and yields (Scheme 6). a-Aminonitrile 16 (R = Ph) could then be converted to a-aminoamide 17 in several steps. Aromatic, aliphatic, heterocyclic and a,/f-unsaturated imines 15 were used as general substrates in these reactions. The origin of the highly enantioselective cataylsis by 14 is believed to be attributed to the simultaneous activation of imines and trimethylsilyl cyanide by the... 

The Strecker reaction is defined as the addition of HCN to the condensation product of a carbonyl and amine component to give a-amino nitriles. Lipton and coworkers reported the first highly effective catalytic asymmetric Strecker reaction, using synthetic peptide 43, a modification of Inoue s catalyst (38), which was determined to be inactive for the Strecker reactions of aldimines (see Scheme 6.5) [62], Catalyst 43 provided chiral a-amino nitrile products for a number of N-benzhydryl imines (42) derived from substituted aromatic (71-97% yield 64->99% ee) and aliphatic (80-81% yield <10-17% ee) aldehydes, presumably through a similar mode of activation to that for hydrocyanations of aldehydes (Table 6.14). Electron-deficient aromatic imines were not suitable substrates for this catalyst, giving products in low optical purities (<10-32% ee). The a-amino nitrile product of benzaldehyde was converted to the corresponding a-amino acid in high yield (92%) and ee (>99%) via a one-step acid hydrolysis. 

L. Yet, Recent Developments in Catalytic Asymmetric Strecker-Type Reactions, Angew. Chem. Int. Ed. 2001, 40, 875-877. 

Job A, Janeck CF, Bettray W, Peters R, Enders D (2002) Tetrahedron 58 2253 Josephsohn NS, Kuntz KW, Snapper ML, Hoveyda AH (2001) Mechanism of enantioselective Ti-catalyzed Strecker reaction peptide-based metal complexes as bifunctional catalysts. J Am Chem Soc 123 11594—11599 Juhl K, Gathergood N, Jprgensen KA (2001) Catalytic asymmetric direct Man-nich reactions of carbonyl compounds with alpha-imino esters. Angew Chem Int Ed Engl 40 2995-2997... 

Ishitani, H., Komiyama, S., Hasegawa, Y., Kobayashi, S. Catalytic Asymmetric Strecker Synthesis. Preparation of Enantiomerically Pure a-Amino Acid Derivatives from Aidimines and Tributyitin Cyanide or Achirai Aidehydes, Amines, and Hydrogen Cyanide Using a Chiral Zirconium Catalyst. J. Am. Chem. Soc. 2000,122, 762-766. 

Takamura, M., Hamashima, Y., Usuda, H., Kanai, M., Shibasaki, M. A catalytic asymmetric Strecker-type reaction promoted by Lewis acid-Lewis base bifunctional catalyst. Chem. Pharm. Bull. 2000,48, 1586-1592. 

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