The salts, 2-methyl-5,5-disubstituted 4,5-dihydroisoxazolium methylsulfates comprising various substituents at the C-3 carbon atom were subjected to transformations. The structure of applied compounds permitted to monitor the effect of this factor on the transformation course of the 2-isoxazoline ring. The nucleophilic addition of cyanide anion to the selected salts enabled the obtaining of a next heterocyclic system of changed physicochemical and biological properties in comparison to the starting 2-isoxazolines. The diastereoselective hydrolysis of the cyanide group in 2-isoxazolidines by the bacteria strain Rhodococcus rhodochrous PCM 909 leads to the obtaining of a racemic mixture of the trans-hydroxyacid. The introduction of new functional groups into the heterocyclic ring made these compounds attractive objects for further chemical and microbial transformations and to study their biological activity.