7-oxabicycloheptane carboxylic acid protaglandin analog intermediates useful in the preparation of anti-thrombotic and anti-vasospastic compounds and method for preparing same

A method for preparing an aldehyde of the structure ##STR49## which comprises providing an amine of the structure ##STR50## wherein R.sup.7 is aryl or lower alkyl, R.sup.8 is H, aryl or lower alkyl, and R.sup.9 is H, OH or lower alkyl, reacting the amine with an anhydride of the structure ##STR51## to form an imide of the structure ##STR52## subjecting the imide to a Grignard reaction by treating same with (1) C.sub.2 H.sub.5 MgCl or C.sub.2 H.sub.5 MgBr (where R.sup.9 is OH) and an aryl Grignard reagent of the structure ##STR53## or (2) R.sup.a Li and ##STR54## (where R.sub.9 .noteq.OH), to form a compound of the structure ##STR55## treating the above with a reducing agent to form the compound of the structure ##STR56## and treating the above alcohol with optional base and then acid to form the intermediate aldehyde.