Carbostyril derivative or a pharmaceutically acceptable acid addition salt thereof, having excellent platelate aggregation inhibitory effect, calcium antagonism, hypotensive effect and phosphodiesterase inhibitory effect are useful as prophylactic or treating agents for thrombosis, circulation improving agents for coronary blood flow such as coronary vasodilators, hypotensive agents and phosphodiesterase inhibitors. Furthermore, the carbostyril derivatives are weak in heart rate increasing activity and also in cardiac muscle contraction increasing activity, and the carbostyril derivatives are useful agents for curing and treating heart diseases such as cardiac angina and myocardial infarction caused by hypercoagulability of the platelets. Processes are disclosed for preparation of the carbostyril derivatives.
α-Acetyllactones are accessed by Mukaiyama-Claisen reactions. Attempts at direct 7-membered ring closure, by either intramolecular alkylation of 4-iodobutyl acetoacetate or olefin metathesis from allyl 2-allyl-3-oxobutanoate, afford exclusively dimeric 14-membered ring products instead of the expected caprolactones.