Synthesis of serine analogues to be used as modified phospho acceptor sites in substrates of protein kinase C

Serine and threonine analogues (compounds 2-6) are readily accessible by reaction of the anion of N,N-dibenzylglycine ethyl ester (1) with an appropriate carbonyl compound. These analogues will be incorporated into Protein Kinase C (PKC) substrates. The serine aldehyde derivative 7 was used for the preparation of the corresponding diethyl acetal 9. This compound was the starting material in the synthesis of the suicide precursor 8, featuring a reductive amination leading to 12 and a Lewis-acid-catalysed cyclization giving 8.