Abstract: The invention disclosed herein relates to novel 1-deoxyglycosides, preferably 1-deoxy-D-mannopyranosides and 1-deoxy-L-rhamnopyranosides, having in the 1-position of the pyranose ring an aralkylthio/aralkenylthio, aralkyloxy/aralkenyloxy or aralkanoylamino/aralkenoylamino substituent; and to novel processes for preparing these 1-substituted-1-deoxyglycosides starting with the corresponding tetra-O-acetylglycopyranosyl bromide or amine. The 6-hydroxy group of 1-substituted-1 deoxyglycopyranosides can also be replaced by other functional groups. These aralkylthio/aralkenylthio, aralkyloxy/aralkenyloxy and aralkanoylamino/aralkenoylamino 1-deoxyglycosides are potent inhibitors of antigen-specific T-cell proliferation and are also useful as inhibitors of delayed-type hypersensitivity reactions.