Synthesis and pyrolysis of two novel pyrrole ester flavor precursors

• Published in: Journal of heterocyclic chemistry Vol. 59; no. 8; pp. 1397 - 1406
• Main Authors: Fan, Wenpeng, Chu, Wenjuan, Tian, Haiying, Zhang, Zhan, Feng, Yingjie, Gao, Ziting, Cheng, Biao, Ji, Xiaoming, Lai, Miao
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Inc 01.08.2022; Wiley Subscription Services, Inc
• Subjects: Additives; Alkylation; Aroma; Benzoic acid; Esterification; Flavors; Gas chromatography; Infrared spectroscopy; Mass spectrometry; NMR; Nuclear magnetic resonance; Oxidation; Precursors; Pyrolysis; Raw materials; Stability analysis; Thermal degradation; Thermogravimetry
• ISSN: 0022-152X; 1943-5193
• DOI: 10.1002/jhet.4479

In 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. Two new pyrrole ester flavors precursors were synthesized using glucosamine hydrochloride and methyl acetoacetate as raw materials. TG‐DTG‐DSC and Py‐GC/MS methods were used to analyze the heating‐stability of the target compounds. The results indicated that these precursors could produce some fragrance compounds which were important in cigarette and heat‐processed food flavoring.