NYSE Euronext ( NYX) is in talks to buy the smaller American Stock Exchange, according to the Wall Street Journal. The Big Board owner has emerged as a frontrunner to but the privately held Amex, which has flirted with exchange operators in Canada and Germany in recent months, the Journal said, citing people familiar with the matter. Analysts say the deal could be worth about $350 million, the paper reported. The deal would be considerably cheaper than some of NYSE Euronext's other potential targets, including Nymex Holdings ( NMX), operator of the New York Mercantile Exchange, which has a market capitalization of about $11 billion. NYSE Euronext has been busy on the acquisition front over the past several years. Under recently departed CEO John Thain, the Big Board bought electronic trading platform Archipelago Holdings and European exchange Euronext. Thain left the company in November to take the top job at Merrill Lynch ( MER). He was succeeded by Duncan Niederauer. NYSE Euronext shares were up fractionally, while Nymex shares were down 2.5% to $117.63 in Wednesday afternoon trading.