Reactions of 3-carboxymethylrhodanine (1) with aldehydes (2a-u) afforded stereoselectively the 5-mono-alkylmethylidene-3-carboxymethylrhodanines (3a-u). The configuration of the 5-monoalkylmethylidene-3-carboxymethylrhodanine (3k) were examined by X-ray structure analysis and confirmed to be Z-configuration. The stereoselective reaction path was discussed. Several 5-dialkylmethylidene-3-carboxymethylrhodanines (15a-f) and alkylamino derivatives of 3-carboxymethylrhodanines (18a-o) were also prepared. These products were evaluated for aldose reductase-inhibitory potency and half of them exhibited valuable inhibitory potency.

Various azaazulene derivatives were synthesized and their antiallergic activity was examined. The structure-activity relationship among various derivatives modified by introducing substituents at the 1-,2-, or 3-position of the azaazulene ring was investigated. The inhibitory activities on allergic histamine release of the compounds bearing a 5-tetrazolyl group at the 3-position were more potent than those of the corresponding compounds with other groups (CN, COOH, and CHO). The compounds substituted with amino, azide and carboxymethylamino groups at the 2-position showed strong inhibitory activity. The compounds with various phenylalkyl groups at the 1-position showed a greater activity than those with other substituents. Among the compounds with substituents at the 1-,2-, or 3-position of the azaazulene ring, 1-benzyl-7-isopropyl-3-(5-tetrazolyl)-1-azaazulen-2-one (18f) and 1-(4-fluorobenzyl)-7-isopropyl-3-(5-tetrazolyl)-1-azaazulen- 2-one (19c) had the most potent inhibitory activities on histamine release from mast cells and on passive cutaneous anaphylaxis (PCA) in rats after oral administration (ED50 = 0.56 and 0.58 mg/kg, respectively).

Various benzo[b]furan derivatives with a carboxymethylsulfamoyl group were prepared and evaluated for aldose reductase-inhibitory potency. Most of the compounds displayed significant inhibitory activities (IC50, 10(-8)-10(-7) M). Among the test compounds, the compounds having a carboxymethylsulfamoyl group at the 3- or 4-position exhibited the greatest inhibitory potency. Structure-activity trends of the tested compounds are discussed.

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