A method for preparing 2-hydroxy-5-[2-(4-(trifluoromethylphenyl)ethylamino)]benzoic acid is proposed. The method may include protection, condensation, and hydrolysis. By means of the screening of a hydroxyl protecting reagent for a starting material, for example, 2-(4-trifluoromethyl)phenethylalcohol and the optimization of other process parameters, the contents of meta-isomer impurities and disubstituted impurities in a target product are effectively controlled. Accordingly, the quality of the product is significantly improved, the reaction yield is also greatly improved, and the improved product quality can satisfy related requirements of preparation research.

A method for preparing 2-hydroxy-5-[2-(4-(trifluoromethylphenyl)ethylamino)]benzoic acid is proposed. The method may include protection, condensation, and hydrolysis. By means of the screening of a hydroxyl protecting reagent for a starting material, for example, 2-(4-trifluoromethyl)phenethylalcohol and the optimization of other process parameters, the contents of meta-isomer impurities and disubstituted impurities in a target product are effectively controlled. Accordingly, the quality of the product is significantly improved, the reaction yield is also greatly improved, and the improved product quality can satisfy related requirements of preparation research.

A method for preparing 2-hydroxy-5-[2-(4-(trifluoromethylphenyl)ethylamino)]benzoic acid is proposed. The method may include protection, condensation, and hydrolysis. By means of the screening of a hydroxyl protecting reagent for a starting material, for example, 2-(4-trifluoromethyl)phenethylalcohol and the optimization of other process parameters, the contents of meta-isomer impurities and disubstituted impurities in a target product are effectively controlled. Accordingly, the quality of the product is significantly improved, the reaction yield is also greatly improved, and the improved product quality can satisfy related requirements of preparation research.

The present invention relates to an N,N-diurea derivative represented by the following general formula (1) and a method for producing the same. In addition, the present invention relates to a thermosensitive recording material in which a thermosensitive recording layer including a basic dye which is colorless or lightly colored at room temperature and a developer capable of developing color upon contact with the basic dye by heating is provided on a base sheet, wherein the developer is the N,N-diurea derivative represented by the following general formula (1): ##STR00001## (wherein R2 is an alkyl group, an aralkyl group, or an aryl group; and A1 is a hydrogen atom or an alkyl group).

The present invention relates to an N,N-diurea derivative represented by the following general formula (1) and a method for producing the same. In addition, the present invention relates to a thermosensitive recording material in which a thermosensitive recording layer including a basic dye which is colorless or lightly colored at room temperature and a developer capable of developing color upon contact with the basic dye by heating is provided on a base sheet, wherein the developer is the N,N-diurea derivative represented by the following general formula (1): ##STR00001## (wherein R2 is an alkyl group, an aralkyl group, or an aryl group; and A1 is a hydrogen atom or an alkyl group).

A method for preparing a lisinopril intermediate is provided. The method includes: treating (R)-hydroxy-4-phenylbutyrate with sulfonyl chloride in an organic solvent in the presence of a base to obtain a solution of sulfonate; reacting the obtained solution with a salt of trifluoroacetyl lysine; and obtaining a N.sup.2-[1-(S)-alkoxycarbonyl-3-phenylpropyl]-N.sup.6-trifluoroacetyl-L-lysine by separating after the reaction is completed. The method provided has a shorter synthesis route, is easy to operate, has a low cost, and is suitable for industrial production.

A method for preparing a lisinopril intermediate is provided. The method includes: treating (R)-hydroxy-4-phenylbutyrate with sulfonyl chloride in an organic solvent in the presence of a base to obtain a solution of sulfonate; reacting the obtained solution with a salt of trifluoroacetyl lysine; and obtaining a N.sup.2-[1-(S)-alkoxycarbonyl-3-phenylpropyl]-N.sup.6-trifluoroacetyl-L-lysine by separating after the reaction is completed. The method provided has a shorter synthesis route, is easy to operate, has a low cost, and is suitable for industrial production.

A process for the preparation of a polyunsaturated thiol comprising: (1) reacting a polyunsaturated alcohol in the presence of a compound of formula R.sub.2SO.sub.2Hal wherein R.sub.2 is a C.sub.1-20 hydrocarbyl group, such an C.sub.1-10 alkyl group, to form a polyunsaturated sulphonyl ester; (2) converting the polyunsaturated sulphonyl ester to a polyunsaturated thioester by reacting with an anion of formula .sup.SC(O)R.sub.4 wherein R.sub.4 is a C.sub.1-20 hydrocarbyl group; (3) converting the polyunsaturated thioester to form a polyunsaturated thiol optionally in the presence of an antioxidant, e.g. using a metal carbonate. (4) reacting said polyunsaturated thiol with a compound (LG)R.sup.3COX wherein X is an electron withdrawing A group and R.sup.3 is an alkylene group carrying a leaving group (LG), such as LG-CH.sub.2 forming (I) where X is an electron withdrawing group and LG is a leaving group; optionally in the presence of an antioxidant, so as to form a polyunsaturated ketone compound.

##STR00001##

A process for the preparation of a polyunsaturated thiol comprising: (1) reacting a polyunsaturated alcohol in the presence of a compound of formula R.sub.2SO.sub.2Hal wherein R.sub.2 is a C.sub.1-20 hydrocarbyl group, such an C.sub.1-10 alkyl group, to form a polyunsaturated sulphonyl ester; (2) converting the polyunsaturated sulphonyl ester to a polyunsaturated thioester by reacting with an anion of formula .sup.SC(O)R.sub.4 wherein R.sub.4 is a C.sub.1-20 hydrocarbyl group; (3) converting the polyunsaturated thioester to form a polyunsaturated thiol optionally in the presence of an antioxidant, e.g. using a metal carbonate. (4) reacting said polyunsaturated thiol with a compound (LG)R.sup.3COX wherein X is an electron withdrawing A group and R.sup.3 is an alkylene group carrying a leaving group (LG), such as LG-CH.sub.2 forming (I) where X is an electron withdrawing group and LG is a leaving group; optionally in the presence of an antioxidant, so as to form a polyunsaturated ketone compound.

##STR00001##

A process for the preparation of a polyunsaturated thiol comprising: (1) reacting a polyunsaturated alcohol in the presence of a compound of formula R.sub.2SO.sub.2Hal wherein R.sub.2 is a C.sub.1-20 hydrocarbyl group, such an C.sub.1-10 alkyl group, to form a polyunsaturated sulphonyl ester; (2) converting the polyunsaturated sulphonyl ester to a polyunsaturated thioester by reacting with an anion of formula .sup.SC(O)R.sub.4 wherein R.sub.4 is a C.sub.1-20 hydrocarbyl group; (3) converting the polyunsaturated thioester to form a polyunsaturated thiol optionally in the presence of an antioxidant, e.g. using a metal carbonate. (4) reacting said polyunsaturated thiol with a compound (LG)R.sup.3COX wherein X is an electron withdrawing A group and R.sup.3 is an alkylene group carrying a leaving group (LG), such as LG-CH.sub.2 forming (I) where X is an electron withdrawing group and LG is a leaving group; optionally in the presence of an antioxidant, so as to form a polyunsaturated ketone compound.

##STR00001##