A compound selected from the group consisting of a compound of the formula ##STR1## wherein the dotted lines represent a possible endo or exo double bond, R.sub.1 and R.sub.2 are individually selected from the group consisting of hydrogen, alkyl of 1 to 8 carbon atoms, alkenyl and alkynyl of 2 to 8 carbon atoms, aryl of 6 to 14 carbon atoms, aralkyl of 7 to 18 carbon atoms and ##STR2## R'.sub.2 is alkyl of 1 to 8 carbon atoms or aryl of 6 to 14 carbon atoms, X is --O-- or --NR--, R is selected from the group consisting of --OH, hydrogen, ##STR3## and --COOR', R' is hydrogen or alkyl of 1 to 8 carbon atoms, Y is selected from the group consisting of hydrogen, alkyl of 1 to 8 carbon atoms and alkenyl and alkynyl of 2 to 8 carbon atoms, all optionally substituted with at least one halogen or --OH, with the proviso that if Y is --OH, X is not --NH-- and their non-toxic, pharmaceutically acceptable addition salts of acids or bases having antibacterial and immunological properties.