Important Synthetic Flavor Compounds - Part 13 (2-methoxy 3-isobutyl pyrazine, 2-isopropyl 4-methyl thiazole, 2-isobutyl thiazole, pyridine 2-acetyl pyridine, 2,4,5-trimethyl oxazole, trithioacetone)

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22 Mar 2026 • 11 min read

Part 13 (2-methoxy 3-isobutyl pyrazine 2-isopropyl 4-methyl thiazole 2-isobutyl thiazole pyridine 2-acetyl pyridine 2,4,5-trimethyl oxazole trithioacetone.)

These are among the 128 synthetic flavor compounds that John Wright, in his book Flavor Creation, suggests every flavorist should know and work with. Part 13 is the last part of the 128 flavor compounds.

Here's the revised content with CAS numbers, standardized formatting, regulatory clarity, safety details, and expanded technical information for each compound:

Important Synthetic Flavor Compounds - Part 13 (Enhanced Edition)

2-Methoxy-3-Isobutyl Pyrazine

CAS Number: 24683-00-9
FEMA Number: 3132
Regulatory Status: FEMA GRAS. International Note: In China, it is regulated as a synthetic food flavor and can only be used for that functional purpose in specific food categories with maximum content limits.
Flavor Note(s): Powerful green, characteristic of green bell pepper and green peas. It is a key component of the harsh green odor of galbanum. The odor is strong, diffusive, and green.
Odor Threshold: Extremely low. Threshold value in red wine is estimated to be 15 ng/L (parts per trillion). In water: approximately 2–10 ppt.
Compounds That Render Similar Flavor Note: 2-Methoxy-3-methylpyrazine (earthy, nutty, less green), 2-Methoxy-3-ethylpyrazine (earthy, potato), 2-Isopropyl-3-methoxypyrazine (green pepper, earthy).
Compounds Often Used Together With: Used with other green notes such as undecatriene isomers to build complex galbanum and vegetable profiles. Also used in coffee and green-floral compounds such as petitgrain.
All Potential Applications: Vegetable flavors (green bell pepper, green peas), coffee flavors, and green-floral compounds. It also occurs naturally in grapes and red wine, contributing to the green bell pepper character in certain varieties.
General Usage Levels: Extremely potent. In finished products, usage levels are typically in the low ppb range (0.1–5 ppb). For flavor concentrates: use as 0.0001–0.001% (1–10 ppm in concentrate) due to extreme potency. Common dilution: 0.01% or 0.1% in propylene glycol or triacetin for safe handling.
Safety & Handling: Colorless clear liquid. Flash point: 176°F (80°C). Store in a cool, dark place in tightly sealed containers, protected from light and air. Use adequate ventilation or fume hood when handling. Due to extreme potency, olfactory fatigue can occur rapidly; use diluted solutions for evaluation. Shelf life: 24 months when stored properly.

2-Isopropyl-4-Methyl Thiazole

CAS Number: 15679-13-7
FEMA Number: 3555
Regulatory Status: FEMA GRAS. Approved for use in food flavors globally.
Flavor Note(s): A fruit flavor intensifier with a peach flavor and distinct vegetable and tropical notes. Used in peach, apricot, nectarine, durian, mango, pear, and blackcurrant flavors. The odor is described as a green, vegetable note.
Odor Threshold: Approximately 1–5 ppb in water (potent)
Compounds That Render Similar Flavor Note: 2-Isobutylthiazole (green, tomato leaf, less fruity), other thiazole derivatives with fruity-green profiles.
Compounds Often Used Together With: Used with other fruity esters (ethyl butyrate, γ-decalactone) and tropical notes in peach, mango, and other tropical fruit flavor complexes.
All Potential Applications: Peach, apricot, nectarine, durian, mango, pear, and blackcurrant flavors. Present naturally in Indonesian durian fruit, red tomatoes, yeast extract, coriander seed oil, and roast meats.
General Usage Levels: Used at low levels due to its potency as a flavor intensifier. In finished products: 0.05–2 ppm. In flavor concentrates: 0.0005–0.02% (5–200 ppm). For peach and tropical applications, start at lower end and adjust upward as needed.
Safety & Handling: Colorless to pale yellow liquid. Flash point: 118°F (48°C) (cc). Soluble in alcohol and propylene glycol; insoluble in water. Store in a cool, dry place away from ignition sources. Flammable; use proper grounding when transferring. Use with adequate ventilation. Shelf life: 12–24 months when stored properly.

2-Isobutyl Thiazole

CAS Number: 18640-74-9
FEMA Number: 3134
Regulatory Status: FEMA GRAS
Flavor Note(s): Green, wasabi, privet, tomato leaf, earthy, vegetable, metallic, musty, waxy. The flavor is green, vegetable, tomato, raw, musty. It adds the characteristics of ripe tomatoes.
Odor Threshold: Approximately 0.2–2 ppb in water (very potent)
Compounds That Render Similar Flavor Note: 2-Isopropyl-4-methyl thiazole (peach-tropical, less green), other thiazoles with green-vegetable character.
Compounds Often Used Together With: Used with other green and vegetable notes in tomato, vegetable, and savory flavor complexes. It enhances the flavor of fresh lime and is used in blackcurrant, papaya, melon, raspberry, and roast beef flavors.
All Potential Applications: Tomato, blackcurrant, papaya, melon, raspberry, roast beef, and fresh lime flavors. Also used in vegetable and savory applications where a green, tomato leaf note is desired.
General Usage Levels: High odor strength; recommended smelling in a 0.10% solution or less. In finished products: 0.05–2 ppm. In flavor concentrates: 0.0005–0.02% (5–200 ppm). For tomato leaf and green vegetable notes, use at 0.1–0.5 ppm in finished product.
Safety & Handling: Colorless to pale yellow clear liquid. Flash point: 135°F (57.2°C). LogP (o/w): approximately 1.715. Soluble in alcohol; stable in most media. Store in a cool, dry place in tightly sealed containers, protected from light. Use appropriate personal protective equipment (gloves, safety glasses). May cause skin sensitization in susceptible individuals.

Pyridine

CAS Number: 110-86-1
FEMA Number: 2966
Regulatory Status: FEMA GRAS for use as a synthetic flavor. International Note: In China, it is regulated as a synthetic food flavor and can only be used for that functional purpose in specific food categories with maximum content limits. Due to toxicity profile, usage is restricted in many jurisdictions.
Flavor Note(s): Sharp, pungent, fishy, and unpleasant odor at high concentrations. At very low dilutions, can contribute roasted, nutty, and meaty nuances.
Odor Threshold: Approximately 10–100 ppb in water (pungent, fishy at higher concentrations)
Compounds That Render Similar Flavor Note: Picolines (2-, 3-, 4-methylpyridine), other nitrogen-containing heterocycles with pungent, fishy, or roasted notes.
Compounds Often Used Together With: Used sparingly with other pyridines, pyrazines, and thiazoles in savory, roasted, and meat flavor complexes to add depth and authenticity.
All Potential Applications: Synthetic food flavor (limited to this functional purpose). Used in small amounts in savory, roasted meat, coffee, and cocoa flavors.
General Usage Levels: Used at extremely low levels due to its potent and unpleasant odor. In finished products: typically 0.01–0.5 ppm. In flavor concentrates: 0.0001–0.005% (1–50 ppm). Always use as a highly diluted solution (0.01–0.1%) for formulation work.
Safety & Handling: Toxic and highly flammable. Flash point: 68°F (20°C). Handle with extreme care using appropriate PPE (chemical-resistant gloves, safety goggles, lab coat). Use only in a fume hood with adequate ventilation. Store in a cool, well-ventilated area away from ignition sources, heat, and incompatible materials (oxidizers, acids). Keep container tightly sealed. Shelf life: 24 months when stored properly. Note: Due to toxicity, consider alternatives when possible.

2-Acetyl Pyridine

CAS Number: 1122-62-9
FEMA Number: 3251
Regulatory Status: FEMA GRAS
Flavor Note(s): Popcorn, corn chip, fatty, tobacco, musty, nutty. The flavor is cornmeal, nutty, bready. It is often referred to as "popcorn pyridine."
Odor Threshold: Approximately 0.5–5 ppb in water
Compounds That Render Similar Flavor Note: 2-Acetyl-1-pyrroline (popcorn, but more intense and roasty), 2-acetylthiazole (popcorn, nutty), 2-acetyl-3-methylpyrazine (popcorn, roasted), other acetyl-substituted heterocycles.
Compounds Often Used Together With: Used with other pyrazines, thiazoles, and furanones in popcorn, corn chip, bread, nut, and coffee flavor complexes. Commonly paired with 2,3-dimethylpyrazine and 2-ethyl-3-methylpyrazine for roasted notes.
All Potential Applications: Popcorn, corn chip, bread, roasted nut, coffee, cocoa, and tobacco flavors. Occurs naturally in bread wheat, cocoa, coffee, filbert, lamb, peanut, potato chip, and tea leaf.
General Usage Levels: High odor strength; recommended smelling in a 1.00% solution or less. Substantivity: 9 hours at 100.00%. In finished products: 0.1–5 ppm. In flavor concentrates: 0.001–0.05% (10–500 ppm). For popcorn and corn chip applications: 1–3 ppm in finished product.
Safety & Handling: Pale yellow to brown clear liquid. Flash point: 164°F (73.3°C). LogP (o/w): 0.85. Soluble in alcohol, dipropylene glycol, and ethyl ether; slightly soluble in water. Store in a cool, dry place in tightly sealed containers, protected from light. May cause skin and eye irritation; use appropriate gloves and safety glasses. Shelf life: 12–24 months.

2,4,5-Trimethyl Oxazole

CAS Number: 20662-84-4
FEMA Number: 4394
Regulatory Status: FEMA GRAS (Publication No. 23). JECFA Flavor Number 1553. Listed in FDA's Substances Added to Food (EAFUS) database.
Flavor Note(s): Nutty, green, roasted, with subtle earthy and musty undertones. Contributes to roasted and savory profiles at low levels.
Odor Threshold: Not well established; estimated in the low ppb range (1–10 ppb) based on related oxazoles.
Compounds That Render Similar Flavor Note: 2,4,5-Trimethylthiazole (more sulfurous, nutty), 2-Ethyl-4,5-dimethyloxazole (similar profile), other alkyl-substituted oxazoles and pyrazines.
Compounds Often Used Together With: Used with pyrazines, thiazoles, and other roasted notes in nut, coffee, cocoa, and savory flavor complexes to add depth and roasted character.
All Potential Applications: Flavoring agent or adjuvant for nut flavors (peanut, hazelnut), roasted coffee, cocoa, bread, and savory applications.
General Usage Levels: Due to typical potency of oxazoles, usage levels are likely in the low ppm range. Recommended starting range in finished products: 0.1–3 ppm. In flavor concentrates: 0.001–0.03% (10–300 ppm).
Safety & Handling: Colorless to pale yellow liquid. Store in a cool, dry place in tightly sealed containers, protected from light. Stable under normal storage conditions. Use appropriate personal protective equipment. Flash point: approximately 140–160°F (60–70°C). Soluble in alcohol and organic solvents; sparingly soluble in water. Shelf life: 24 months when stored properly.

Trithioacetone (2,2,4,4,6,6-Hexamethyl-1,3,5-trithiane)

CAS Number: 828-26-2 (for the trithiane isomer mixture)
FEMA Number: 3475
Regulatory Status: FEMA GRAS (Note: Verify current status on latest FEMA GRAS lists)
Flavor Note(s): Powerful, tropical, passionfruit, guava, durian, with a sulfurous, juicy, and slightly catty nuance. Provides an authentic tropical fruit character at extremely low concentrations.
Odor Threshold: Extremely low; estimated in the low ppt to sub-ppb range
Compounds That Render Similar Flavor Note: 4-Mentha-8-thiol-3-one (black currant, catty), 3-mercaptohexanol (tropical, passionfruit), other sulfur-containing heterocycles with tropical character.
Compounds Often Used Together With: Used with other sulfur compounds (mercaptans, thioesters) and fruity esters (ethyl butyrate, ethyl hexanoate, allyl caproate) in passionfruit, guava, and durian flavor complexes. Also pairs with δ-decalactone for peach-tropical nuances.
All Potential Applications: Passionfruit, guava, durian, and other tropical fruit flavors for beverages, candies, dairy products, and confectionery.
General Usage Levels: Extremely potent. Used at very low levels, typically in the parts per billion (ppb) range in finished products: 0.1–5 ppb. In flavor concentrates: 0.0001–0.001% (1–10 ppm). Always handle as a highly diluted solution (0.01–0.1%) due to potency.
Safety & Handling: Crystalline solid with a melting point around 24°C (75°F); may be liquid at room temperature depending on isomeric composition. Exists in cis and trans isomeric forms. As a potent sulfur compound, requires careful handling to prevent olfactory fatigue. Store in tightly sealed containers under inert gas (nitrogen) to prevent oxidation. Protect from light and heat. Use fume hood when handling. Use PTFE or glass containers; avoid prolonged contact with soft plastics. Shelf life: 12–18 months when stored properly under inert gas.

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