Abstract: A process for increasing the color-free shelf life of a crude N-acetyl aminophenol prepared by the acetylation of an aminophenol wherein the N-acetyl aminophenol contains color-forming impurities which are the products of oxidation of the aminophenol and other side reactions. The process comprises dissolving the crude N-acetyl aminophenol in a solvent containing a reducing agent, heating the solution at about the boiling point, crystallizing the N-acetyl aminophenol from the solution, washing the crystalline N-acetyl aminophenol with solvent containing reducing agent and thereafter separating and drying the crystalline N-acetyl aminophenol.

Abstract: An improved pharmaceutically active derivative of a copolymer of olefin monomer and .alpha.,.beta.-unsaturated polycarboxylic anhydride is prepared by reacting the copolymer with aqueous ammonia, spray drying the resulting aqueous solution of half-amide, half-ammonium salt and thermally imidating the resulting substantially dry, solid particulate product by simultaneous treatment with elevated temperature and removal of water until 5-40% of the derivative half-amide, half-ammonium salt groups are converted to imide groups.

Abstract: A process for the preparation of .alpha.-L-aspartyl-L-phenylalanine alkyl esters wherein L-phenylalanine is reacted with N-protected-L-aspartic anhydride, the resulting product is treated to yield .alpha.-L-aspartyl-L-phenylalanine which is esterified with an alkanol to yield an .alpha.-L-aspartyl-L-phenylalanine alkyl ester which is recovered.Novel precursors for .alpha.-L-aspartyl-L-phenylalanine alkyl esters are prepared in the process of this invention.