What was the name of 1950s cartoon with a monkey named alexander something about not being able to claim his golden crown until he learned certain lesson?

The cartoon you're thinking of is called "Alexander the Greater". It was a 1950s animated short produced by United Productions of America (UPA).

In the cartoon, Alexander is a mischievous monkey who inherits a golden crown, but can't claim it until he learns to control his impulsiveness and become "greater".