German pharmaceutical and chemical company Merck KGaA has agreed to acquire St. Louis-based Sigma-Aldrich Corp., which has manufacturing and distribution facilities in Madison, Verona, Milwaukee and Sheboygan, for $17 billion in cash. Merck officials said Monday that the deal will expand the global reach of its chemical unit EMD Millipore, also known as Merck Millipore, "increasing the company's presence in North America and adding exposure to fast-growing Asian markets." Both Sigma-Aldrich and…