To thoroughly study the functional role of prokaryotic t-RNA-guanine-transglycosylases which are essential in the pathogenesis of shigellosis, novel efficient, high-yielding synthetic approaches for preQ(1) base, Q base, as well as for (ent)-Q base mainly employing cheap and readily available starting materials have been developed. Q base as well as (ent)-Q base are accessible starting from preQ(1) base via nucleophilic substitution reactions with appropriately decorated halocyclopentenyl synthons, prior to that prepared from naturally occurring carbohydrates.