411A
I think you are wrong on that statement as the Lockheed Constellation
C-121A ---749A used a Cyclone BD1 engine which was not a compound engine, however it did have Fuel injection.
This engine had the two fuel injector pumps synchronised by a mechanical interconnecting rod, where as on the later compound engines I believe they were synchronised by individual flow sensors.
the C-121a were introduced during 1947 if I remember correctly