Blackstone Group L.P. said Thursday its Blackstone Infrastructure Partners unit has agreed to acquire a majority stake in Tallgrass Energy LP for about $3.3 billion in cash. Affiiates of the Singaporean sovereign wealth fund GIC will be a minority investor in the deal, which is expected to close in the first quarter. "This transaction represents a rare opportunity to invest in a large-scale U.S. midstream infrastructure platform that connects high-production supply basins to key markets and is underpinned by long-term contracts," Sean Klimczak, global head of infrastructure at Blackstone said in a statement.