Synthesis of some 2-methoxy-3-alkylpyrazines with strong bell pepper-like odors

Abstract

The synthesis, mass spectra, and infrared spectra are described for four new 2-methoxy-3-alkylpyrazines with alkyl groups hexyl, propyl, isopropyl, and ethyl. The odor thresholds of the hexyl, propyl, isopropyl, and ethyl compounds were found to be 1, 6, 2, and 425 parts of compound per 1012 parts of water, respectively. The odor character of these four compounds compared to that of the known bell pepper component 2-methoxy-3-iso-butylpyrazine are described as very similar for the hexyl and propyl, moderately similar for the isopropyl, and not similar for the ethyl. The related

Characterisation of the aroma of green Mexican coffee and identification of mouldy/earthy defect

“…MiPP was mentioned as responsible of the peasy defect in green and roasted Ruanda coffees and quantified at 2.5 ppm [34]. Its odour threshold was between 2 and 20 ppt in water [35]. MsBP has never before been identified in coffee, but is known to be present in vegetables, such as carrots, lettuce, peas, sweet and bell pepper, pumpkin, and beetroot, and also in Swiss type cheeses, white wine, and ginger [36].…”

Purification and characterisation of an odorant‐binding protein from cow nasal tissue

“…This latter compound has interesting properties for being a good probe for olfactory binding proteins since it has a very low olfactory threshold in humans ( 2 parts/1012) [6] and specific anosmia can be demonstrated indicating the presence of binding proteins of high affinity to 'green' odorants. The binding affinity (Kd 1.2 pM) and ligand specificity of this proteins in cows are now well characterised [5,7,IS].…”

Stable Isotope Dilution Gas Chromatography-Mass Spectrometry for Determination of Methoxypyrazines (“Green” Aroma) in Wine

“…Identification proceeded rapidly in the late 1960sand early 1970swith the development of gas chromatographymass spectrometry (GC-MS). Studies focused on bell peppers (Buttery et al 1969a,b;Seifert et al 1970;Murray et al 1970),potatoes Buttery and Ling 1973;Meigh et al 1973;Nursten and Sheen 1974) and other vegetables (Murray and Whitfield 1975). Structures of the methoxypyrazines 1,2 and 3 were identified, their extremely low sensory detection thresholds were established, and their structures were confirmed by synthesis.…”

“…The trideuterated methoxypyrazine internal standards were synthesised essentially by the methods of Seifert et al (1970) and Murray and Whitfield (1975). The retention time difference between trideuterated isobutylmethoxypyrazine (5) and isopropylmethoxypyrazine (3) requires use of both the trideuterated isobutyl-and trideuterated isopropylmethoxypyrazines, 5 and 6, respectively, for accuracy of quantitative analysis.…”

“…2-Methoxy-3-(2-methylpropyl) pyrazine (1) (isobutylmethoxypyrazine) has an odour threshold of 1-2 ng r' in water (Buttery et al 1969a,b;Seifert et al 1970Seifert et al , 1972 and has been widely used in studies of odorant binding to olfactory mucosa (Pelosi et al 1982), including isolation of odorant-binding proteins (Bignetti et al 1985;Pes and Pelosi 1995), and in studies of the response of olfactory neuronal cultures to odorant binding (Ronnett et al 1991). The aroma of this methoxypyrazine is described as bell pepper-like (Buttery et al 1969a,b;Seifert et al 1970Seifert et al , 1972Parliment and Epstein 1973;Murray and Whitfield 1975;Takken et al 1975), green (Takken et al 1975), and slightly musty or leafy (Maga 1989). The methoxypyrazine occurs in the berries of some grape varieties, particularly those of Sauvignon blanc and Cabernet Sauvignon vines, and it is incorporated into the wines of these grape varieties in a concentration that can provide distinctive aroma.…”