AbstractNew phenanthridines substituted in the 6‐position by a β‐aminoethylthiol chain have been synthesized. These new products are easily obtained from 6‐methylphenanthridine by a Mannich reaction or from 6‐bromophenanthridine by substitution. From the 6‐carboxaldehydophenanthridine and the β‐amino‐ethylthiol, the corresponding thiazolidine or imine are obtained. These compounds are likely to be new radioprotectors.