The oxidation of N-methyl-N-5-hexenylhydroxylamine with mercuric oxide and the condensation between 5-hexenal and N-methylhydroxylamine afforded cis-S-methyl-3-oxa- 2-azabicyclo [3.3. 0~ octane(2). Other bicyclic isoxazolidines have been synthesized by the condensation reaction employing unsaturated aldehydes and unsaturated ketones. The structures of these compounds were proved by hydrogenolysis and, in some cases, ...