Chirped-pulsed FTMW spectra of valeric acid, 5-aminovaleric acid, and δ-valerolactam: A study of amino acid mimics in the gas phase

► The CP-FTMW spectra of valeric acid (VA) and δ-valerolactam (DVL) have been observed. ► The 5-amino VA derivative (AVA) is folded into a structure that is stabilized by an n → π* interaction. ► The so-stabilized AVA is transformed into DVL upon heating. ► Similar reactions do not occur with α, β, or γ amino acids, enhancing their evolutionary relevance in biological systems. ► CP-FTMW spectra of two water complexes of VA also have been observed.