| 摘要 |
Preparation of coconut flavored two chiral centered 5-isobutyl-3-methyl-4,5-dihydro-2(3H)-furanone (I) involves converting a bifunctional acyclic monoterpene ketone, dihydrotagetone isolated from plant species of Tagetes. (I) is a new analog of natural whisky lactone and coconut aldehyde. Conversion of a bifunctional acyclic monoterpene ketone dihydrotagetone (II), isolated from the plant species Tagetes into coconut flavored two chiral centered 5-isobutyl-3-methyl-4,5-dihydro-2(3H)-furanone of formula (I) involves: (a) Adsorbing Tagetes minuta oil on an adsorbent selected from alumina or silica gel; (b) Loading adsorbent obtained from step (a) on a soxhlet extractor and washing with a non polar solvent (cold percolation) selected from petroleum ether or hexane for removing the non polar constituents; (c) Isolating the dihydrogetone (II) rich fraction using hot hexane percolation with increasing percentage of ethylacetate (0.2 - 5)%; (d) Concentrating the separated fractions under reduced pressure to obtain (II) rich concentrate; (e) Loading the concentrate on alumina or silica gel column and eluting the column with a non polar solvent selected from hexane or petroleum ether; (f) Eluting the column further with increasing percentage of ethyl acetate (up to 5)% in hexane; (g) Concentrating the resulting hexane-ethylacetate fractions under reduced pressure to obtain (II) in at least 99% purity; (h) Providing (II) in organic solvent selected from ether selected from tetrahydrofuran, dimethoxyethane or dioxane, alcohol selected from butanol or t-butyl alcohol, ketone selected from acetone or methyl ethyl ketone; (i) Oxidizing (II) in presence of an oxidizing reagent selected from sodium meta-periodate, potassium meta-periodate or ruthenium tetraoxide in the range of 2 - 8 times moles of (II) and a co-oxidizing agent selected from potassium permanganate or sodium permanganate in the range of 0.1 - 0.6 times mole of (II); (j) Adding a base selected from sodium carbonate, sodium bicarbonate, potassium carbonate, lithium carbonate or sodium hydroxide in the range of (1 - 4 times of (II)) to the above solution; (k) Maintaining the temperature between -15 - 90 deg C during oxidation from (h) to (j) for 4 - 48 hours; (l) Destroying the excess permanganate from the above reaction mixture with saturated solution of sodium bisulfite or sodium metabisulfite; (m) Filtering the above reaction mixture, washing, acidifying and removing the solvent under reduced pressure, followed by extraction and chromatography to obtain 2,6-dimethyl-4-oxo-heptanoic acid (III) with at least 68% yield; (n) Providing (III) under stirring in a solvent selected from tetrahydrofuran, dimethoxyetane or dioxane, alcohol (e.g. methanol, butanol and t-butyl alcohol) and chlorinated solvent (e.g. dichloromethane and chloroform); (o) Adding a base selected from sodium bicarbonate, sodium hydroxide or potassium carbonate to the resultant solution to make salt of the oxy acid of (III); (p) Reducing salt of oxo acid of (III) to hydroxy acid in the presence of reducing agent selected from sodium borohydride or lithium aluminum hydride in the range of 0.5 - 3 times mole at reaction temperature -15 - 50 deg C; and (q) Removing the organic solvent under vacuum and acidifying the cooled aqueous alcoholic solution at -10 - 0 deg C with an acid selected from hydrochloric acid, sulfuric acid, acetic acid or acetic anhydride for 30 minutes - 8 hours and finally isolating 5-isobutyl-3-mehtyl-4,5-dihydro-2(3H)-furanone of formula (I) (also named as 4-isobutyl-2-methyl-4-butanolide) in at least 76% yield by extraction and chromatography. Independent claims are also included for the following: (1) a stable compound (III) as an analog of natural 2,6-dimethyl-5-oxo-heptanoic acid found in essential oil of Mentha x piperita, having acidic sweet aroma, containing oxo and carboxylic acid, capable of undergoing conversion into several value added products such as corresponding 4-oxo ester, 4-hydroxy ester and 4-hydroxy acid by estrification and |
