sour grapes
Disparaging what one cannot obtain, as in The losers' scorn for the award is pure sour grapes. This expression alludes to the Greek writer Aesop's famous fable about a fox that cannot reach some grapes on a high vine and announces that they are sour. In English the fable was first recorded in William Caxton's 1484 translation, "The fox said these raisins be sour."