Three men have been charged by German prosecutors for allegedly plotting an attack on a synagogue in Heidelberg or a Jewish institution in Frankfurt, authorities said on Tuesday. The alleged leader of the plot, a 25-year-old German, allegedly tried to travel to Syria and join Islamist extremist fighters there, according to prosecutors. After his travel plans failed, he allegedly began planning a terrorist attack on the synagogue in Heidelberg or a Jewish institution in Frankfurt together with an 18-year-old man in a chat. Their hope was that an attack would end the close cooperation between Ge…