Abstract: The preparation method of the powder of which dissolution rate improves is characterized by including of the process that slightly soluble drug having acidic group (e.g., 3-(5-{2-[5-methyl-2-(4-methylphenyl)-1,3-oxazol-4-yl]ethoxy}-3,4-dihydronaphthalen-1-yl)propanoic acid etc.) is made to metal salt solution and is neutralized to precipitate. By the method of the present invention, since a powder of which specific surface area increases and dissolution rate improves can be obtained, it is excellent as a preparation method of drug bulk.

Abstract: The present invention relates to a method for the preparation of active ester, characterized by subjecting to a reaction a mixture of a carboxylic acid, which is a starting material, reagent which forms active ester and a base or a starting material carboxylic acid.

Abstract: Flat filaments have a flatness (A/B) of 7 to 25, where A is a length of at least one of the two longer sides of a substantially rectangular, transverse cross-section of each filament and B is a length of at least one of the two shorter sides of the substantially rectangular, transverse cross-section of each filament. The flat filaments also have a fineness of 0.5 to 40 denier, and are provided on each of the two longer sides with one or more ribs continuously extending in a direction of an axis of the filament and having a width W and a height H. The number of the ribs on each longer side ranges from 1 to A/2W, the rib width W ranges from B/2 to 3B, and the rib height H ranges from B/2 to 2B. The filaments have excellent nontackiness and bulkiness and permit easy elimination of crimps by polishing, and can be suitably used as raw fibers which, when formed into a pile product, provide the pile product not only with a soft feeling but also with resilient and substantial feeling.