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We prepared two isoxazol [5,4-b] piridin-3-acetic acids by two different synthetic methods. 4,6-Dimethylisoxazole [5,4-b] pyridin-3-acetic acid was obtained by reaction with hydroxylamine of 4-hydroxy-5,7-dimethyl-2H-pyrano [2,3-b]pyridin-2-one, which was in turn prepared starting from 2-hydroxy-3-acetyl-4,6-dimethylpyridine. Isoxazolo [5,4-b] pyridine-3-acetic acid was obtained starting from 3-methyl-5-aminoisoxazole and has shown interesting auxin activity.

Some azomethine type compounds from 3-nitroisoxazole-5-carboxy-aldehyde were synthesized; among these the most active, oxime (III a), shows bacteriostatic activity in vitro against gram--comparable to that of nitrofurantoin.

As a part of a systematic research on new heterocyclic 3,4,5-trimethoxybenzamides with potential C.N.S. depressant activity, some derivatives of methyl- or dimethyloxazolidines were prepared. The results of preliminary pharmacological screening are reported in comparison with those of the model compound (I).

By reaction of suitable hydroxamic acids chlorides with beta-ketoesters, we have prepared the ethyl esters of isoxazol-4-carboxylic acids, substituted in the 3- and 5-positions with 4-pyridyl and o-chlorophenyl groups, and some of their esters and amides of pharmaceutical interest. 3-(4-Pyridyl)-5-(o-chlorophenyl)isoxazole was obtained either by decarboxylation of the acid or by oxidation of the syn and anti oximes of 3-(o-chlorophenyl)-1-(4-pyridyl)-2-propen-1-one; from the syn oxime the corresponding isoxazoline was also obtained. Pharmacological screening shows that some of the new compounds have a myolytic activity.

Reaction of 2,3,5,6-tetramethylphenacyl halides with formamide did not produce the expected 4(5)-(2,3,5,6-tetramethylphenyl)imidazole, but 4(5)-(2,3,5,6-tetramethylbenzoyl)imidazole (VII) was isolated as the major product together with 5-(2,3,5,6-tetramethylphenyl)oxazole (III), alpha-formylamino-2,3,5,6-tetramethylacetophenone (IV) and alpha-chloro-beta-amino-vinyl 2,3,5,6-tetramethylphenyl ketone (IX) as by-products. The corresponding mesitylene derivatives gave analogous results, whereas 4(5)-(2-methylphenyl)imidazole was obtained from 2-methylphenacyl bromide as expected according to the Bredereck's reaction. The structure of the isolated compounds were elucidated by element analysis, mass, I.R., U.V. and N.M.R. spectra, and by chemical reactivity.