Sullivan & Cromwell is advising Tokio Marine Holdings, Japan’s largest insurer by market value, on its agreement to buy U.S.-based HCC Insurance Holdings for $7.5 billion.

Baker & McKenzie and Debevoise & Plimpton have scored lead advisory roles on Japan’s Dai-ichi Life Insurance Co’s agreement to buy American insurer Protective Life for $5.7 billion in what is the largest ever acquisition by a Japanese insurer.