Aristeromycin and neplanocin A are two naturally occurring carbocyclic
nucleosides isolated from Streptomyces citricolor. They belong to a s
mall family of cyclopentane-containing natural products that are deriv
ed from carbohydrates, in this case D-glucose, as the ultimate biosynt
hetic precursor. This review outlines our current understanding of the
biosynthesis of aristeromycin and neplanocin and proposes possible me
chanisms for the conversion of carbohydrates into 5-membered ring carb
ocycles.