Boca Raton, Fla. — ODP Corp., the parent company of Office Depot, has rejected USR Parent Inc.’s off-market transaction offer to acquire the Boca Raton, Fla.-based retailer. USR, the parent company of office products retailer Staples and affiliate of Sycamore Partners, offered to buy ODP for $40 per share in an all-cash deal that would equate to roughly $2.1 billion. In a letter to Stefan Kaluzny, managing director of Sycamore Partners and a member of the board of directors at USR, ODP’s chairman of the board of directors Joseph Vassalluzzo …