The company sold a San Francisco office tower, 123 Mission St., for about $300 million to Northwood Investors LLC. : (Bloomberg)—China’s beleaguered HNA Group Co. is continuing to whittle down its real estate holdings as it seeks to reduce its massive debt load. The company sold a San Francisco office tower, 123 Mission St., for about $300 million to Northwood Investors LLC, according to people with knowledge of the matter. HNA made a small profit, having paid $255 million for the property in August 2016.