The present invention provides compounds of formula (I) ##STR1##

the prodrugs thereof, and the pharmaceutically acceptable salts of the compounds and prodrugs, wherein R, R", R", and Z are as defined herein; pharmaceutical compositions thereof; and uses thereof in treating diabetes, insulin resistance, diabetic neuropathy, diabetic nephropathy, diabetic retinopathy, cataracts, hyperglycemia, hypercholesterolemia, hypertension, hyperinsulinemia, hyperlipidemia, atherosclerosis, and tissue ischemia.