The other two bidding groups included J.C. Flowers & Co and Toronto Dominion bank, according to sources familiar with the matter.
Regulators seized the troubled Florida lender last month and sold it to a consortium that includes Wilbur Ross’s WL Ross, Carlyle Group, Blackstone and Centerbridge Partners.
Private equity firms have increasingly turned their attention to banking as the number of troubled U.S. banks and thrifts increases, although BankUnited was not the first failed bank to be bought by private investors.
Hedge fund and private equity investors, including Flowers, bought the assets of failed U.S. mortgage lender IndyMac earlier this year, for example.