If you describe someone's behaviour or opinion as sour grapes, you mean that that person is angry because they have not got or achieved something that they wanted.酸葡萄(指由于得不到而贬低某物)
I don't think it's such a great job - and that's not just sour grapes because I didn't get it.我认为这份工作不怎么样——我可不是因为吃不着葡萄说葡萄酸。