Electrospray ionization mass spectrometry study on dipeptide 4-chlorobutyl ester produced from refluxing of amino acid with phosphoryl chloride in tetrahydrofuran.

Phosphoryl chloride was able to promote the formation of peptide and the ringopening of tetrahydrofuran (THF) followed by a sequence of successive reactions by simply refluxing. ESI multistage tandem mass spectrometry was applied to trace the reaction and elucidate the product structures, dipeptide 4-chlorobutyl ester.