Furanones are a series of five-membered heterocyclic compounds, which generally could be divided into 3(2H)-furanones and 2(5H)-furanones according to the positions of carbonyl.
In the matrix structure of 3(2H)-furanones, the positions of 2, 4, 5 could be substituted. For 2(5H)-furanones, the positions of 3, 4, 5 could be substituted, and they can also form fused ring, especially the positions of 3, 4, easy to be fused with benzene ring.
The fused ring compounds of Furanones are mainly used in pigments and API intermediates. The research on them is not thorough as 3(2H)-furanones and 2(5H)-furanones. Here we mainly introduce the research progress on 3(2H)-furanones and 2(5H)-furanones.
- Monocyclic 3(2H)-furanones
Scientist has found many 3(2H)-furanones play important role in some aroma compounds, such as 2,5-dimethyl-4-hydroxy-3(2H)-furanone (3); 2,5-dimethyl-3(2H)-furanone (4); 5-methyl-4-hydroxy-3(2H)-furanone (5); 5-methyl-2-ethyl-4-hydroxy-3(2H)-furanone (6); 5- methylol-2-methyl-4-hydroxyl-3(2H)-furanone (7).
The characteristics and applications of some most common aroma 3(2H)-furanones derivatives:
|3||Also called as Strawberry Furanone, isolated from strawberry and pineapple, also existing in beef soup, having a smell of sweet burnt brown caramellic cotton candy savory like maltol. Odor threshold is only 4*10-11. The effect of its aroma enhancement is remarkable and the smell lasts long.||Commercial name Furaneol, FEMA3174, widely used as flavouring agent in candy, chocolate, meat, milk, instant noodle, drink, wine, soup, tomato sauce, tobacco, cosmetics.|
|Intermediate for furaneol|
|5||The main ingredient of soy sauce, with a soybean odor, can be isolated from beef soup, arctic berry and mango, also has caramel, hot beef, and fried chicory root odor.||FEMA3635, can be used as flavouring agent for good, alcohol beverage.|
|6||Exist as a mixture of two tautomers, found in molasses and soybean sauce, be considered having a sweet odor, reminiscent of cake and ripe fruit smell,||FEMA3623, can be used as flavouring agent for meat or meaty food.|
|7||with a caramel odor||–|
- Monocyclic 3(5H)-furanones
Some of Monocyclic 3(5H)-furanones are the ingredient of flavoring materials, such as 4,5-dimethyl-3-hydroxyl-2(5H)-furanone (8). 3-chloro-4(dichloromethyl)-5-hydroxyl-2(5H)-furanone(9), which were found to be human carcinogens, formed as the main disinfection by-product during the chlorination process of water treatment, has attracted many attention. The researches about MX, toxicity, formation, reaction of this compound and even the similar bromide compound in running water are quite active.
There are also 2(5H)-furanones, as active ingredients in some important traditional Chinese medicine, such as Anemonin(10) in Clematis Root. However the most popular ones in pharma research, still is the drug with similar chemical structure, such as Non-steroidal anti-inflammatory drug (NSAID) Rofecoxib(11), and other 2(5H)-furanones as intermediates.
Overall, current research about furanones are broad and deep and there are various applications about 3(2H)-furanones and 2(5H)-furanones. The flavouring substances containing 3(2H)-furanone as key ingredient have great economic benefits, since their raw material is easy to get and the reaction condition is mild. 2(5H)-furanones are innovative drugs which either exists in nature or can be synthesized. The research about synthesis of them is of great significance. Moreover, The synthesis of new chiral compounds and high-tension ring compounds and etc from various chiral 2(5H)-furanones has drawn more and more attention.