Simpson Thacher & Bartlett, Davis Polk & Wardwell, Clifford Chance and two leading Swiss firms have taken the lead on the largest outbound M&A deal ever by a Chinese company.

Chinese state-owned China National Chemical Corp., better known as ChemChina, announced this week a $43 billion acquisition of Swiss agrochemical giant Syngenta AG. The deal, which has its roots in China’s desire to secure a sustainable food supply for its surging population, comes after nearly a year of negotiations between both companies. And some old legal hands have a hand in the matter.