Abstract: The invention discloses new benzoindole styryl compounds and its use for a high-density optical recording medium. The invention uses the dyes of the new benzoindole styryl compounds to form the recording layer of high-density recording media. The new benzoindole styryl compounds are easy to prepare and purify, so they are cheaper when comparing to the compounds generally used in high-density optical recording media. The benzoindole styryl compounds has a maximum absorption for the light wavelength in the range of 500 nanometers to 700 nanometers. The benzoindole styryl compounds also have high sensitivity and chemical stability for light and heat. Using the new benzoindole styryl compounds to form a high-density optical recording medium can match up with the short-wavelength laser beam for high-density optical recording media and have the advantage of a stable quality.

Abstract: This invention provides azo-metal complex dyes for a high-density optical disc recording medium having the following formula (I): wherein R1 reprents C1-8 alkoxyl, carboxy, C1-8 alkoxycarbonyl, or amide; R2, R3, R4 and R5 can be the same or not, which are hydrogen, C1-8 alkyl, C1-8 alkoxyl, carboxy, C1-8 alkoxycarbonyl; C1-6 alkylaminealkylenecarboxy, amide, nitro, trifluoro-methyl, sulfonic acid fluoride group, sulfonic acid group or halogen atom; X reprents carbon or nitrogen atom; and M reprents Mg+2, Mn+2, Co+2, Ni+2, Cu+2 or Zn+2, These azo-metal complex dyes whose spectra are capable of matching wavelength of 400 nm˜700 nm visible light can be used as a high-density optical disc recording medium.

Abstract: A process for the purification of water-soluble non-ionic contrast agents from water-soluble non-ionic impurities involves the steps of (a) injecting a raw water-soluble non-ionic contrast agent solution on a chromatographic column containing non-ionic resins; (b) eluting water-soluble impurities contained in the raw water-soluble non-ionic contrast agent solution with deionized water as a first eluent, and (c) eluting a water-soluble non-ionic contrast agent with alcohol as a second eluent.

Abstract: A process for the purification of water-soluble non-ionic contrast agents from water-soluble non-ionic impurities involves the steps of (a) injecting a raw water-soluble non-ionic contrast agent solution on a chromatographic column containing non-ionic resins; (b) eluting water-soluble impurities contained in the raw water-soluble non-ionic contrast agent solution with deionized water as a first eluent, and (c) eluting a water-soluble non-ionic contrast agent with alcohol as a second eluent.

Abstract: This invention provides azo-metal complex dyes for a high-density optical disc recording medium having the following formula (I): 1

Abstract: A process for preparing an angiotensin converting enzyme inhibitor. Phosphorus pentachloride is reacted with the carboxylic acid group of an amino acid to form an acyl chloride hydrochloride. The resulting hydrochloride salt is then coupled with a silylated amino acid in a non-aqueous medium to form a high yield peptide. The peptide is used as an angiotensin converting enzyme (ACE) inhibitor.

Abstract: A method is provided for the preparation of derivative of 3-benzylthio-2-alkylpropionic acid of formula (I): ##STR1## wherein X is independently selected from hydrogen, C.sub.1 -C.sub.6 alkyl or C.sub.1 -C.sub.6 alkoxyl, and R is independently selected from hydrogen or C.sub.1 -C.sub.10 alkyl. An alkyl acrylic acid of formula (III): ##STR2## wherein R is as defined above, is reacted with a substituted .alpha.-toluenethiol of formula (II): ##STR3## wherein X and R are as defined above, at a stoichiometric mole ratio and in the presence of quaternary ammonium salts or quaternary phosphonium salts serving as phase transfer catalysts at a temperature ranging from 100.degree.-150.degree. C.Derivatives of 3-benzylthio-2-alkylpropionic acid are obtained in high yield and high purity.