Amino reaction with aldehyde groups

Gives white aminated cotton. Borohydride reduces yellow Schiff bases formed by reaction of aldehyde groups with amino groups... 

Similarly to the asymmetric synthesis by imines and oxazoline, there is also a chiral hydrazone, (S)-l-amino-2-(methoxymethyl)pyrrolidine 51a, which gives chiral hydra-zones on reaction with aldehydes and ketones104, and is able to form an intermolecular chelate with the methoxy group. Enders and coworkers used this system for enantioselec-tive aldol reaction105, and for synthesis of chiral ketone104 and aldehyde106 (equation 30). 

The identity of (CCXVII, m.p. 94—5° C) was chemically established by showing the presence of an exocychc amino group. The reaction with aldehydes to give Schiff s bases and the deamination with nitrous acid both occur very readily. These reactions, especially the latter, are characteristic of an amino group attached to the nitrogen atom of a heteroring. The same tjqie of isomer formation has been observed with ammonium dithiocarbazate and [Pg.172]

Pyridoxal phosphate, a derivative of vitamin Be, acts as coenzyme in transamination and decarboxylation reactions. In a transamination reaction the aldehyde group of pyridoxal phosphate first forms a Schiffbase with the amino group of the amino acid, which is then converted to keto acid. Pyridoxal phosphate is thereby converted to pyridoxamine phosphate which transfers the amino group to an other keto acid to form the corresponding amino acid. 

Chitosan is a multi-nucleophilic polymer due to the presence of the NH2 and OH functional groups. The initial sites where substitution occurs are the more nucleophilic amino groups. However, the experimental conditions and protection of the NH2 groups reduces the intermolecular hydrogen bonding and creates space for water molecules to fill in and solvate the hydrophilic groups of the polymer backbone (Sashiwa and Shigemasa 1999). A -alkylated derivatives can be obtained by the treatment of chitosan with aldehydes or ketones via formation of Schiff base intermediates, aldimines (from reactions with aldehydes), or ketimines (from reactions with ketones) followed by reduction of the imine with sodium borohydride. 

However, in contrast to isothiosemicarbazides, where coordination to the metal ion leads to the loss of nucleophilicity of end aminogroups, isothiocarbohydrazides on binding to the metal ion still have one non-coordinated amino group, which bears a non-bonded electron pair capable of nucleophilic attack on electrophiles. Another distinction is the chemical equivalence of the end amino groups towards condensation reactions with aldehydes and ketones. This difference is displayed advantageously in the one-pot template sjmthesis of octaazamacrocyclic systems. 

Reaction products of reactive aldehydes derived from oxidised lipids, such as acrolein, ( )-4-hydroxynon-2-enal and malondi-aldehyde, with lysine, arginine and other amino acids are described as examples in Section 4.7.5.6. These products, ALE (advanced lipoxidation end products), formed in vivo are markers of oxidative stress in the organism. Reaction mechanisms are discussed in Section 3.8.1.12.1. As the final reaction products, proteins and oxidised lipids also form dark insoluble macromolecular products that contain variable proportions of lipid and protein fractions. In particular, such products include protein oligomers, proteins with oxidised sulfur amino acids, proteins containing imine bonds (C=N) formed by reaction with aldehydes or hydroperoxides (they mostly arise from the -amino group of bound lysine) and... 

There also exists an acidregioselective condensation of the aldol type, namely the Mannich reaction (B. Reichert, 1959 H. Hellmann, 1960 see also p. 291f.). The condensation of secondary amines with aldehydes yields Immonium salts, which react with ketones to give 3-amino ketones (=Mannich bases). Ketones with two enolizable CHj-groupings may form 1,5-diamino-3-pentanones, but monosubstitution products can always be obtained in high yield. Unsymmetrical ketones react preferentially at the most highly substituted carbon atom. Sterical hindrance can reverse this regioselectivity. Thermal elimination of amines leads to the a,)3-unsaturated ketone. Another efficient pathway to vinyl ketones starts with the addition of terminal alkynes to immonium salts. On mercury(ll) catalyzed hydration the product is converted to the Mannich base (H. Smith, 1964). 

In the Strecker synthesis an aldehyde is converted to an a-amino acid with one more carbon atom by a two-stage procedure in which an a-fflnino nitrile is an intenne-diate. The a-fflnino nitrile is fonned by reaction of the aldehyde with ffliimonia or an fflTtmonium salt and a source of cyanide ion. Hydrolysis of the nitrile group to a carboxylic acid function completes the synthesis. 

---