Fox will eat just about anything when he’s hungry enough so when he saw bunches of grapes hanging from vines above him he did his best to leap up and get them.

All his efforts failed.  The grapes were just out of his reach. Fox turned away thinking that the fruit was no doubt green and sour and that he wouldn’t want those grapes if they fell on him.

Aesop says it’s easy to despise what you can’t have.