Prostaglandin (PG.sub.1) derivatives having (1) a 6-keto feature, together with a 9-deoxy-9-hydroxymethyl feature for example ##STR1## or (2) a 9-deoxy-6,9-epoxymethano feature together with a 5-halo or 6-hydroxy feature, for example ##STR2## or a 5,6-didehydro feature, for example in an enol ether of the formula ##STR3## said derivatives having pharmacological activity. Processes for preparing them and the appropriate intermediates are disclosed.