there are provided compounds of the formula ## str1 ## wherein r 1 is a substituted or unsubstituted divalent aliphatic group of 1 to 16 carbon atoms ; wherein the substituents are mono or poly and are selected from the group consisting of lower alkyl , aryl and arlkyl , r 3 is selected from the group consisting of same group of values as r 5 , r 5 is selected from the group consisting of substituted and unsubstituted alkyl of 1 - 10 carbon atoms , aryl , cycloalkyl and heterocycloalkyl of 3 - 8 carbon atoms , wherein the substituents are mono or poly and are selected from the group consisting of lower alkyl , cycloalkyl of 3 - 8 carbon atoms , lower alkenyl , lower alkynyl , nitro , lower alkoxy , lower alkoxycarbonyl , phenyl loweralkyl , phenyl , mono and polyhalophenyl , phenoxy , mono and polyhalophenoxy , r 6 and r 7 may be the same or different and are hydrogen , alkanoyl or alkoxyalkanoyl , r 7 may also have the same value as r 5 , y is oxygen or sulfur , m is 0 or 1 , q is 0 or 1 , wherein the prefix alk designates moieties which are straight chain or branched chain , and the term lower designates 1 - 6 carbon atoms and the unmodified term alk signifies 1 - 24 carbon atoms , the respective tautomers thereof , the pharmaceutically acceptable salts and addition salts thereof and the hydrates of said salts and addition salts . there are further provided methods of protecting subjects liable thereto from infections caused by an organism of the group plasmodium sp ., mycobacterium sp . and pneumocystis carinii by administering to a subject liable to such infection , a prophylactically effective amount of a compound of the foregoing formula . these compounds will also reduce the level of infection where said subjects have already been infected .