| 摘要 |
A process for the manufacture of 3-hydroxy-2-alkyl-4-pyrones of formula I is provided. <IMAGE> I The process comprises cyclizing a compound of formula II, <IMAGE> II an acidic medium and hydrolyzing the ester formed thereby to produce compound I. R1 represents methyl or ethyl; R2 represents lower alkanoyl or optionally substituted benzoyl; R3 represents -OH or -NR4R5; and, R4 and R5 may be alike or different and represent lower alkyl. The pyrones of formula I wherein R1 represents methyl or ethyl are known flavorants and odorants.
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