The compound of the formula I ##STR1## wherein R, R.sub.3 and R.sub.5 independently represent hydrogen or hydroxy provided that at least one of R, R.sub.3 and R.sub.5 represents hydroxy; R.sub.1 represents hydrogen, lower alkyl, C.sub.3 -C.sub.7 -alkenyl, hydroxy-lower alkyl, optionally substituted cycloalkyl or optionally substituted cycloalkyl-lower alkyl, bicycloalkyl, bicycloalkyl-lower alkyl, adamantyl, tetrahydropyranyl, tetrahydrothiopyranyl, tetrahydropyranyl-lower alkyl, tetrahydrothiopyranyl-lower alkyl, adamantyl-lower alkyl, aryl-hydroxy-lower alkyl, aryl, aryl-lower alkyl, aryl-C.sub.3 -C.sub.6 -cycloalkyl, 9-fluorenyl, 9-fluorenyl-lower alkyl or cycloalkenyl-lower alkyl; or R.sub.1 represents a bicyclic benzo-fused 5 or 6-membered saturated cyabocyclic radical or a benzo-fused 5 or 6-membered saturated heterocyclic radical containing a heteroatom selected from oxygen and sulfur directly attached to the fused benzene ring, any said bicyclic radicals being optionally substituted on the benzo portion by lower alkyl, lower alkoxy or halogen, or R.sub.1 represents any said bicyclic radical substituted-lower alkyl; R.sub.2 represents hydrogen, halogen, --S--R.sub.1 ', --NR.sub.b --R.sub.1 ', or --NH--R.sub.1 ' in each of which R.sub.1 ' has meaning as defined for R.sub.1 provided that R.sub.1 ' in --SR.sub.1 ' does not represent hydrogen; R.sub.b represents lower alkyl; R.sub.4 represents hydroxymethyl provided that R.sub.2 does not represent either hydrogen or --NHR.sub.1 ' in which R.sub.1 ' represents either hydrogen or lower alkyl; or R.sub.4 represents lower alkoxymethyl or lower alkylthiomethyl; or R.sub.4 represents --CONHR.sub.6 in which R.sub.6 represents lower alkyl; aryl-lower alkyl, C.sub.3 -C.sub.6 -cycloalkyl or hydroxy-lower alkyl; pharmaceutically acceptable ester derivatives thereof in which free hydroxy groups are esterified in form of a pharmaceutically acceptable ester; and pharmaceutically acceptable salts thereof; methods for their preparation; and their use as adenosine receptor agonists are disclosed.