Abstract: Taurine analogues are used for scavenging active oxygen compounds and preventing and minimizing damage to the skin from ultraviolet rays. The taurine analogues have the following formula: ##STR1## wherein R.sub.1, R.sub.2 and R.sub.3 are as defined in the specification.

Abstract: The present invention concerns an enzyme inhibitor containing the compound represented by the following formula (I) as an effective ingredient: ##STR1## where R represents hydrogen or substituted or not substituted alkyl group, alkenyl group, aryl group or aralkyl group, X represents OR' or NR"R"', in which R', R" and R'" represent respectively hydrogen or substituted or not substituted alkyl group, alkenyl group, aryl group or aralkyl group.The enzyme inhibitor according to the present invention can effectively inhibit aldose reductase, glyoxalase I and reverse transcriptase.

Abstract: Cimetidine, namely N-cyano-N'-methyl-N"-[2-((4-methyl-5-imidazolyl) methylthio) ethyl] guanidine which is useful as an antagonist of H.sub.2 -receptor is prepared by reacting 4-methyl-5-[(2-aminoethyl) thiomethyl] imidazole, which is obtained by the reaction of 4-methyl-5-hydroxymethylimidazole on 2-aminoethanethiolsulfuric acid, with O-alkyl-S-alkyl-cyanothioimidocarbonate to give N-cyano-N'-[2-((4-methyl-5-imidazolyl) methylthio) ethyl]-O-alkylisourea, which is reacted with monomethylamine. According to the present process, cimetidine can be prepared in good yield and desired purity with very reduced amount of methyl mercaptan released from the reaction.

Abstract: A method for preparing 2,2-disubstituted thiazolidine involves reacting aminoalkyl hydrogen-sulfate with a compound having hydrosulfide ion in the presence of ketone. According to the present method, such thiazolidine can be prepared in good yield and desired purity without using harmful ethylenimine as a starting material.

Abstract: A process for preparing a cysteamine-S-substituted compound involves reacting ethyleneimine or ethyleneimine derivatives with a thiosulfate or thiophosphate in the presence of a cation exchanger of a free type. Use of the cation exchanger of a free type in this reaction allows preparation of the cysteamine-S-substituted compound with an amazingly high purity in a high yield.

Abstract: Hexamethylene.bis-dicyandiamide is safely prepared in good yield and desired purity by a novel method which comprises reacting N-cyano-O (or S)-alkyl-iso (or isothio) urea with hexamethylenediamine. The desired product is useful as an intermediate of chlorhexidine which is an antibacterial agent.

Abstract: Salt of pantothenic acid and salt of cystamine or cysteamine are caused to react under the presence of an accelerator selected from the group consisting of carbodiimides and N-hydroxy compounds without any pretreatment thereby producing pantethine or pantetheine, and the pantetheine is oxidized to produce pantethine which is a precursor of co-enzyme A.