The poet called April the cruelest month, and you probably won\u2019t get an argument from Oleg Deripaska. The Russian billionaire\u2019s net worth plunged to a record low on Tuesday, almost three weeks after the U.S. imposed sanctions on him and some of his companies. Deripaska, 50, is the majority shareholder of En+ Group, which was among the firms targeted by the U.S. Treasury on April 6. Since then its stock has tumbled by more than half, reducing the aluminum tycoon\u2019s fortune by $3.8 billion. Along with earlier losses, his net worth has dropped by $4.7 billion this year, the most of any wealthy Russian, according to the Bloomberg Billionaires Index. United Co. Rusal was also among the eight Deripaska-linked firms blacklisted by the U.S. in response to Russia\u2019s \u201cmalign activity around the globe.\u201d EN+ owns a 48 percent stake in Rusal, which produces about 6 percent of the world\u2019s aluminum and operates mines, smelters and refineries around the world. Deripaska was also targeted personally for reasons including threatening the lives of business rivals, bribing government officials and having links to organized crime, according to the U.S. Office of Foreign Assets Control. The billionaire has denied any wrongdoing.