Abstract
An unexpected gas phase Gutknecht self-condensation of D-glucosamine hydrochloride to 2,5-deoxyfructosazine (2,5-DOF) in atmospheric pressure chemical ionization mass spectrometry (APCI-MS) was described. Mechanistic studies indicated that the thermospray conditions in APCI largely accelerate the irreversible Gutknecht self-cyclocondensation reaction of amino-sugars. Our observations provide a promising clue for a new borate-free synthetic method of 2,5-DOF by mimicking the APCI conditions.