Preparation And Application Of7-Oxo Carboxylic Acid Substituted Coumarin Derivatives

High-intensity sweeteners are being used as sugar substitutes in considerable andincreasing amounts in food and beverages. These sweetener compounds are generallyconsidered to be safe for use in foodstuffs. The majority of the high-intensity sweeteners areare high-intensity, low-calorie, high-potency, and/or non-nutritive. High-intensity sweetenersare often cheaper than sucrose and are employed in minute quantities due to their potency inproviding a sweet taste. High-intensity sweeteners can diminish the risk of tooth decay.However, many high-intensity sweeteners such as sodium saccharin, acesulfame steviosidehave an off-taste, unpleasant in character and sometimes characterized as bitter, lingering,metallic. It had been found that certain7-oxo carboxylic acid substituted coumarinderivatives are capable of masking the off-taste of such sweeteners to an unexpected andhighly desirable degree. Sodium-2-[(4-methyl-2-oxo-2H-1-benzopyran-7-yl) oxy]-propionateis one of these compounds. In this paper, we mainly studied the preparation ofSodium-2-[(4-methyl-2-oxo-2H-1-benzopyran-7-yl) oxy]-propionate and its masking effectson the off-taste of high-intensity sweeteners.Firstly, this research uses resorcinol and ethyl acetoacetate as raw material and perchloricacid as catalyst producing4-methyl-7–hydroxycoumarin. Afterwards uses4-methyl-7–hydroxycoumarin and2-bromo-propionic acid ethyl ester as raw material producing2-[(4-methyl-2-oxo-2H-1-benzopyran-7-yl) oxy]-propionate ethyl ester by Williamsonreaction. And then make it hydrolyze under alkaline conditions, successfully producing thetarget product,2-[(4-methyl-2-oxo-2H-1-benzopyran-7-yl) oxy]-propionate. Synthesistechnology has been optimized and the best experimental solution has been confirmed. Thenwe detect the chemical structure of target products and intermediate products to insure theyare what we need with IR and NMR analysis. Finally, we study the masking effects of2-[(4-methyl-2-oxo-2H-1-benzopyran-7-yl) oxy]-propionate on the off-taste of high-intensitysweeteners.In the preparation of4-methyl-7–hydroxycoumarin, we choose perchloric acid replace of concentrated sulphuric acid as catalyst, to catalyze the synthesis of4-methyl-7–hydroxycoumarin in normal temperature. The single-factor experiment and response surfacedesign were used to determine the optimal conditions. The experimental results showed that:When the dose of resorcinol in the reaction system is30mmol. The reaction time is5.3h. Thedose of Perchloric acid is21mL. The mole ratio between ethyl acetoacetate and resorcinol is1.1:1. Under these conditions, the yield of hymecromone is93.19%.In the preparation of2-[(4-methyl-2-oxo-2H-1-benzopyran-7-yl) oxy]-propionate ethylester, the single-factor experiment and orthogonal experiment were used to determine theoptimal conditions. The experimental results showed that: when the dose of4-methyl-7-hydroxycoumarin in the reaction system is5.2851g (30mmol). the mole ratiobetween4-methyl-7-hydroxycoumarin and2-bromo-propionic acid ethyl ester is1：1.8, thereaction temperature is60℃, the reaction time is5h, Catalyst content n(K2CO3): n(4-methyl-7–hydroxycoumarin) is1.5:1. The optimum yield is75.24%.In the preparation of2-[(4-methyl-2-oxo-2H-1-benzopyran-7-yl) oxy]-propionate, thesingle-factor experiment and orthogonal experiment were used to determine the optimalconditions. The experimental results showed that: when the dose of2-[(4-methyl-2-oxo-2H-1-benzopyran-7-yl)oxy]-propionate ethyl ester in the reaction systemis8.25g (30mmol), the reaction temperature is85℃, the reaction time is2h, the mole ratiobetween2-[(4-methyl-2-oxo-2H-1-benzopyran-7-yl) oxy]-propionate ethyl ester and NaOH is1:1, the concentration of NaOH is5%, the dosage of anhydrous ethanol is100mL. Theoptimum yield is78.13%.In order to study the masking effects of2-[(4-methyl-2-oxo-2H-1-benzopyran-7-yl)oxy]-propionate on the off-taste of high-intensity sweeteners, firstly, convert it intowater-soluble sodium-2-[(4-methyl-2-oxo-2H-1-benzopyran-7-yl) oxy]-propionate.The resultsshowed that sodium-2-[(4-methyl-2-oxo-2H-1-benzopyran-7-yl)oxy]-propionate hadbitterness and astringency at relatively higher concentration. When used at200mg/kg, it couldblock the off-taste of saccharin sodium, acesulfame-K and stevia at different levels, enhance salty, inhibit the bitterness of coffee, while do not affect sour, sweet and umami taste.