Interphenylene 8-aza-9-dioxothia-11,12-secoprostaglandins are prepared by the two-stage alkylation of the anion of a lower alkyl sulfonamide, R.sup.1 SO.sub.2 NH.sub.2, using first a compound of the formula: ##STR1## and second, a compound of the formula: ##STR2## The compounds produced have renal vasodilatory activity when administered orally and are therefore useful for treating patients with renal impairment.