Question

Propose a mechanism for the $\mathit{\alpha }\mathbf{,}\mathit{\beta }$-elimination reaction shown on page 1082.

Short answer

Using pyridoxal phosphate (PLP) \(\alpha ,\beta \) positions of amino acids were eliminated to give an imine product. Hydrolysis of the given product results in corresponding amino acid.

Step-by-step solution

Transimination

Transimination reaction attaches an amino acid with coenzyme forming a product with imine between PLP and amino acid.

Proposed mechanism

This mechanism involves\({\bf{\alpha ,\beta }}\)-elimination of an amino acid using pyridoxal phosphate (PLP). In the first step a proton is removed fromcarbon and in next step leaving group eliminate from \({\bf{\beta }}\)carbon. Resultant product undergo transamination reaction gives an enamine which on tautomerization reaction an imine. Hydrolysis of the imine results the final product.The mechanism is shown below

Thus, the prevailing mechanism for the \({\rm{\alpha ,\beta }}\)-elimination reaction is