Preparation of Peptide Aldehyde Collections

Peptide aldehydes are important biochemical tools for specific and reversible inhibition of serine, cysteine, and aspartate proteases in-vitro and in-vivo. Whereas several methods for the preparation of peptide aldehydes have been described [26-28], their reliable parallel synthesis remained a tedious endeavor. Peptide aldehydes suffer from configurational lability in the a-carbonyl position and from high chemical reactivity. 

Racemization of the peptide aldehydes was effected by acid treatment and monitored by H-NMR at 9.3-9.5 ppm. 

CDC13 solution led to the slow formation of a second diastereomer. Heating in dilute acetic acid (60 °C) effected rapid racemization. 

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