Abstractmagnified imageDiastereoisomeric linear and cyclic ‘N‐chiral quaternary ammonium salts’ (QASs) were efficiently synthesized from corresponding L‐amino acids in high yields. The diastereoisomers of each pair of ‘N‐chiral QASs’ were successfully separated. The absolute configurations of these QASs were determined predominately by X‐ray single‐crystal analysis. The 1H‐NMR data of ‘N‐chiral QASs’ provided characteristic information on the configuration of the N‐chiral center. ‘N‐Chiral QASs’ exemplified by [N(R)]‐2a and [N(S)]‐2a are stable in protic and aprotic solvents within a broad pH and temperature range.