The invention relates to a single cycle process for preparing D,L-methionine from an alkali methioninate solution obtained by alkaline hydrolysis of 5-(2-methylmercaptoethyl)hydantoin, in which the D,L-methionine is obtained by neutralizing the alkali methioninate solution with carbon dioxide at elevated temperature and subsequently crystallizing D,L-methionine in the presence of seed crystals.

The invention relates to a single cycle process for preparing D,L-methionine from an alkali methioninate solution obtained by alkaline hydrolysis of 5-(2-methylmercaptoethyl)hydantoin, in which the D,L-methionine is obtained by neutralizing the alkali methioninate solution with carbon dioxide at elevated temperature and subsequently crystallizing D,L-methionine in the presence of seed crystals.

The present invention relates to the technical field of medicine, and specifically relates to the carboxylic acid compound represented by the chemical formula I or chemical formula II, and a pharmaceutically acceptable salt, a prodrug, and a solvate thereof, and a method for preparation thereof, as well as a pharmaceutical composition containing the described substances, and a use thereof.

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A process for the synthesis of Dapsone and intermediates thereof are described.

The invention relates to processes for large-scale diastereoselective syntheses of cycloheptadienylsulfone and stereotetrads, key intermediates for the preparation of Aplyronine A.

The invention relates to processes for large-scale diastereoselective syntheses of cycloheptadienylsulfone and stereotetrads, key intermediates for the preparation of Aplyronine A.

According to one embodiment, in producing polythiols in a manner similar to a conventional method, a polythiol having improved storage stability may be produced in a convenient manner by adjusting reaction conditions so as to prevent thiourea from remaining within products. In particular, the equivalent weight of thiourea to be used in a reaction may be adjusted to a predetermined range, thereby reducing the amount of unreacted thiourea, and thiourea may be removed once more in a sub sequent process, thereby effectively removing remaining thiourea while achieving a high yield. The polythiol thus produced does not contain residual thiourea, and thus does not show discoloration or cloudiness caused by precipitates even under prolonged storage or high-temperature conditions.

According to one embodiment, in producing polythiols in a manner similar to a conventional method, a polythiol having improved storage stability may be produced in a convenient manner by adjusting reaction conditions so as to prevent thiourea from remaining within products. In particular, the equivalent weight of thiourea to be used in a reaction may be adjusted to a predetermined range, thereby reducing the amount of unreacted thiourea, and thiourea may be removed once more in a sub sequent process, thereby effectively removing remaining thiourea while achieving a high yield. The polythiol thus produced does not contain residual thiourea, and thus does not show discoloration or cloudiness caused by precipitates even under prolonged storage or high-temperature conditions.

According to one embodiment, in producing polythiols in a manner similar to a conventional method, a polythiol having improved storage stability may be produced in a convenient manner by adjusting reaction conditions so as to prevent thiourea from remaining within products. In particular, the equivalent weight of thiourea to be used in a reaction may be adjusted to a predetermined range, thereby reducing the amount of unreacted thiourea, and thiourea may be removed once more in a sub sequent process, thereby effectively removing remaining thiourea while achieving a high yield. The polythiol thus produced does not contain residual thiourea, and thus does not show discoloration or cloudiness caused by precipitates even under prolonged storage or high-temperature conditions.

Derivatives of an organic substance containing one or more groups selected from the group consisting of sulfanyl, selanyl and sulfino may be produced by reacting an organic substance containing one or more groups selected from the group consisting of sulfanyl, selanyl and sulfino with an olefin compound containing an ethylene structure having at least two electron-withdrawing groups except halogen atoms under an acidic condition to form a derivative of the organic substance