Chemistry
Strecker Synthesis
Strecker Synthesis is a chemical reaction that produces amino acids from aldehydes or ketones. The reaction involves the addition of hydrogen cyanide to the carbonyl group of the aldehyde or ketone, followed by hydrolysis of the resulting nitrile to form an amino acid. This process is widely used in the production of amino acids for use in the food and pharmaceutical industries.
Written by Perlego with AI-assistance
Related key terms
1 of 5
3 Key excerpts on "Strecker Synthesis"
eBook - ePubComprehensive Enantioselective Organocatalysis
Catalysts, Reactions, and Applications, 3 Volume Set
- Peter I. Dalko(Author)
- 2013(Publication Date)
- Wiley-VCH(Publisher)
30 Hydrocyanation and Strecker Reactions Carsten Kramer and Stefan Bräse30.1 Introduction
In 1850, A. Strecker accidently accomplished the first synthesis of the amino acid alanine by mixing of acetaldehyde, ammonia, and HCN and subsequent hydrolysis of the formed adduct [1]. Whereby this three-component-reaction is in general known as the Strecker reaction, the addition of a cyanide source to a preformed imine species is often referred to as the “modified Strecker reaction,” The so-formed α-amino nitriles, or from cyanide addition to carbonyl compounds the so-obtained cyanohydrins, are versatile building blocks that can be converted, for example, into α-hydroxy carbon acids, amino acids, amino alcohols and diamines.30.1.1 Overview
Several catalysts have been developed for the asymmetric organocatalyzed hydrocyanation of carbonyls and for the Strecker reaction. This chapter divides the catalysts into several subgroups, defined according to important structural motifs responsible for catalytic activity. Each catalyst group will be discussed in detail with regard to substrate scope, limitations, and other important factors. In addition, mechanistic insights will be provided, if transition states are satisfyingly revealed by experimental work or in silico studies.30.2 Amino-Acid Containing Catalysts for Carbonyl Hydrocyanation
In 1981, Inoue and coworker accomplished the first organocatalyzed hydrocyanation of benzaldehyde (1) with reasonable asymmetric induction (Scheme 30.1 ) [2]. By using 2 mol% of the cyclic dipeptide cyclo(l -phenylalanine-l -histidine) (2), benzaldehyde (1) reacted with HCN in benzene at 35 °C to give the cyanohydrin 3
eBook - PDF- D. Obrecht, J.M. Villalgordo(Authors)
- 1998(Publication Date)
- Pergamon(Publisher)
1. Introduction,basic conceptsand strategies As many of the classical multicomponent reactions, the Strecker Synthesis also takes advantage of the versatile chemistry of the initially formed imine. The formation of the amino nitrile, however, is reversible under the reaction conditions which usually results in lower yields. This problem was elegantly solved in the Bucherer-Bergs variation, 374-376 where the initially formed aminonitrile is irreversibly trapped by formation of a hydantoin as depicted in Scheme 1.8.5.5 (entry b). The Mannich reaction 377 (Scheme 1.8.5.6) involved in the biosynthesis of many alkaloids (e.g. tropane alkaloids, gramine) has been synthetically used in many elegant syntheses of alkaloids such as porantherine. 378 Scheme 1.8.5.6 H R 2 .j,,..jj.R 4 O R3 R 5 I~N. + CH20 + = R R 3 v ~ R 5 R R1 ! H ~ ~ N'R2 RlfN. R2 + CH20 + = H H The Erlenmeyer azlactone synthesis (Scheme 1.8.5.7) combining a hippuric acid derivative, acetic anhydride and an aldehyde to form a didehydroazlactone. This azlactone approach has been extensively used for the synthesis of amino acids. 359 Scheme 1.8.5.7 O RI,JJ'-NACOOH + Ac20 + R2-CHO H NaOAc a 2 R 1 O The Biginelli reaction 379,38~ combines ureas with an aldehyde and a [3-oxoacid derivative to form dehydropyrimidones as shown in Scheme 1.8.5.8. 120
eBook - PDF- Petri M. Pihko(Author)
- 2009(Publication Date)
- Wiley-VCH(Publisher)
( R)-amino nitriles are suitable precursors for the synthesis of enantiopure α-quaternary α-amino acids, which are key intermedi- ates for the synthesis of a broad variety of pharmaceutically important compounds. Although the resin-bound Schiff base catalyst 41, which proved efficient in the hydrocyanation of aldimines (Scheme 6.44) also turned out to promote the model Strecker reaction of N-allyl acetophenone imine, long reaction times (180 h) Scheme 6.44 Reaction sequence for the synthesis of enantiopure ( R)- tert-leucine hydrochloride starting from the pivalaldimine Strecker adduct obtained under catalysis with polymer-bound thiourea 41. N Ph H N Ph CN H O cat. 41 (4 mol%) 1. toluene, −78 °C, 15 h 2. Ac 2 O, formic acid 97% yield 92% ee >99% ee (recryst.) N Ph CO 2 H H O 65% (w/v) H 2 SO 4 , 45 °C, 20 h hydrolysis 99% yield NH 3 Cl CO 2 H 1. HCl, 70 °C, 12 h 2. H 2 , Pd/C, MeOH quant. yield 84% yield overall >99% ee (R)-tert-leucine hydrochloride 6.2 Synthetic Applications of Hydrogen-Bonding (Thio)urea Organocatalysts 193 were required to give the desired Strecker adduct ( 41: 95% yield; 85% ee at 4 mol% loading; −75 °C in toluene). Catalyst 42 (2 mol% loading), however, displayed higher catalytic activity under unchanged conditions (97% yield/30 h; 85% ee) and was therefore utilized for the enantioselective hydrocyanation of various N- benzyl-protected ketimines that were found to be the substrates of choice due to higher stability of their Strecker adducts under either acidic or basic conditions (no retro-Strecker decomposition) and due to slightly increased ee values (e.g., N- allyl acetophenone imine: 85% ee; N-benzyl: 90% ee; at −75 °C in toluene) com- pared to N-allyl-protected ketimines.
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
