Facile Synthesis of Orthogonally Protected Optically Pure Keto- and Diketopiperazine Building Blocks for Combinatorial Chemistry

A facile synthesis of cysteine-based diketopiperazine from thiol-protected precursor

l-Cysteine is one of the most promising biomass-based building blocks with great potential applications. Herein, we report a versatile synthetic route to produce cysteine-based 2,5-diketopiperazine (DKP) with good yield from the thiol-ene click reaction of l-cysteine and commercially available acrylates, followed by dimerization of the amino acid intermediates. The achieved DKP diastereomers were successfully separated and fully characterized by spectroscopic methods. Moreover, the chiroptical property of DKP in the presence of various metal ions was investigated by circular dichroism spectroscopy. The potential application of the optically active cysteine-based DKP as a chiral probe for detection of silver ion in water has been demonstrated.

‘Clickable’ 2,5-diketopiperazines as scaffolds for ligation of biomolecules: their use in Aβ inhibitor assembly

The synthesis of 1,3,6-trisubstituted-2,5-diketopiperazine scaffolds bearing up to three ‘clickable’ sites for further oxime bond or alkyne–azide cycloaddition ligations is described.