Alcaloides steroidiques—CLXIV : Isomerisation en presence d'une base ou d'un acide d'oxazirannes steroidiques derives de la conanine

Isomerisation into an imino-carbinol or a nitrone is the first step in the hydrolysis of an oxazirane. This isomerisation, studied on three steroidal compounds lead to the following results: compound 6, bearing cis-oriented 18H and oxazirane ring, gives rise only to the nitrone 13. Compound 1 which bears trans 18H may isomerise either into the imino-carbinol 5 or into the nitrone 11 (11 is quantitatively obtained in acidic conditions with minimum basic catalysis). The case of compound 7 which isomerises whatever the conditions into the α hydroxylated imino-ether 8 shows the influence of structural factors which enhance the mobility of the 18H.