Simpson Thacher & Bartlett is advising buyout firm Blackstone Group on a $1.1 billion acquisition of Indian outsourcing company Mphasis Ltd.

Blackstone is paying $825 million for an 84 percent stake in Mphasis from Hewlett Packard Enterprise Co., the corporation information technology product and solution provider created after the split of legacy Hewlett-Packard Co. in November. The U.S. private equity firm is buying the remaining 26 percent of the Bombay Stock Exchange-listed company from public shareholders. The deal could value Mphasis at up to $1.1 billion and make it Blackstone’s largest acquisition in India.