8-Chlorodibenz [6,/][1, 4] oxazepine-10 (1 lfí)-carboxylic acid, 2-acetylhydrazide (1, SC-19220) has been previously reported by us and others to be a PGE2 antagonist selective for the receptor subtype1 with antinociceptive activities. 2 Analogs of SC-19220, in which theacetyl moiety has been replaced with pyridylpropionyl groups and their homologs, have been synthesized as illustrated by compounds 13 and 29. These and other members of this series have been shown to be efficacious analgesics and PGE2 antagonists of the subtype. This report discusses the structure activity relationships within this series.