Synthesis and pyrolysis of two novel pyrrole ester flavor precursors

Abstract

AbstractIn order to develop the high‐temperature‐released pyrrole aroma, two novel flavors precursors of methyl 2‐methyl‐5‐(((2‐methylbutanoyl)oxy)methyl)‐1‐propyl‐1H‐pyrrole‐3‐carboxylate and methyl 2‐methyl‐5‐(((2‐methylbutanoyl)oxy)methyl)‐1‐propyl‐1H‐pyrrole‐3‐carboxylate were synthesized using glucosamine hydrochloride and methyl acetoacetate as raw materials through cyclization, oxidation, alkylation, reduction, and esterification. The target compounds were characterized by nuclear magnetic resonance (1H NMR, 13C NMR), infrared spectroscopy (IR) and high‐resolution mass spectrometry (HRMS). Thermogravimetry (TG), differential scanning calorimeter (DSC) and the pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS) methods were used to analyze the heating‐stability of the target compounds, and the pyrolysis mechanism was inferred. Py‐GC/MS results indicated that some fragrance compounds were formed during thermal degradation such as 2‐methylbutyric acid, 2‐methylbutyrate, alkylpyrroles, and benzoic acid, which were important aroma components or flavor additives. This provided a theoretical reference for the application of pyrrole ester in cigarette and heat‐processed food flavoring.