Synthesis of diastereomerically pure 1,4,5-substituted-2-oxopiperazines on solid-phase

The first studies toward the solid-phase synthesis of 1,4,5-substituted-2-oxopiperazines are reported. The synthetic strategy is based on reductive alkylation of resin-bound amino acids using N-protected α-amino aldehydes (with concomitant epimerization), followed by acylation with α-chloroacetyl chloride. Subsequent stereoselective on-bead intramolecular cyclization has led to a diastereomerically pure 2-oxopiperazine.