Imine products Strecker amino acid synthesis

As has been outlined for the Strecker synthesis, the Ugi reaction also proceeds via initial formation of a Schiff base from an aldehyde and an amine. The imine intermediate is attacked by the isocyanidc, a process which is supported by protonation of the imine by the carboxylic acid component. The resulting a-amino nitrilium intermediate is immediately trapped by the carboxylate to give an 6>-acyl imidiate. All steps up to this stage are reversible. Only the final oxygen to nitrogen acyl shift is irreversible and delivers the A-acyl-a-amino amide as the thermodynamically favored product which contains two amide groups. 

Strecker synthesis a method used to synthesize an amino acid an aldehyde reacts with NH, forming an imine that is attacked by cyanide ion. Hydrolysis of the product gives an amino acid. 

All of the reactions shown are fairly standard in type. The first is a Strecker synthesis the first formed product is the a-aminonitrile, which is then hydrolyzed to an amino acid. The second reaction is a standard oxime synthesis as the ketone is symmetric, there is no stereochemistry to worry about. In (c), an imine is formed the stereochemistry about the carbon-nitrogen double bond is determined by steric hindrance. Since the SM is racemic, two diastereoisomers will be formed, hence the wavy bond to the methyl group. In the final example, a hydrazine is prepared while it s not possible to be certain of the stereochemistry about the C=N double bond, it s logical to assume that the less sterically hindered isomer will predominate ... 

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