Serine Octamer Substitution Reactions With α‐Hydroxy Acids

RATIONALE: The amino acid serine forms chiral magic number clusters, which can be studied using mass spectrometry (MS). Serine octamer clusters are also known to incorporate one or two nonserine monomers with serine monomers to make up the octamer. METHODS: A Thermo LTQ ion trap mass spectrometer with nanoelectrospray ionization (nESI) was used to study cluster formation by both kinetically and energy-resolved methods. This study validates past observations on the homochiral preference of serine octamer during its association with other nonserine monomers. RESULTS: A substrate scope covering α-hydroxy acids and related molecules was studied. The chiral preference was investigated with tandem MS and the importance of salt bridge formation and α/β-carbon hydrogen bonding was recognized. CONCLUSIONS: Weak interactions involving steric forces, salt bridges, ion-dipole interactions, and hydrogen bonds control stereoselective and chiroselective properties of the serine octamer cluster.