Roger Crandall, a co-chief operating officer at Massachusetts Mutual Life Insurance Company, will become president of the company Dec. 1.

Stuart Reese, who has been chairman, president and chief executive officer, will continue to be chairman and CEO.

William Glavin Jr., the other MassMutual co-COO, who has been head of the U.S. insurance group, will take over as chief executive of the company’s OppenheimerFunds Inc. unit Jan. 1, 2009, MassMutual says.

John Murphy, the current head of OppenheimerFunds, will stay on as chairman until he retires at the end of 2009, MassMutual says.

Crandall and Glavin have been co-COOs at MassMutual since July 2007.

Crandall, who has been MassMutual’s chief investment officer as well as a co-COO, began working for MassMutual in 1988. He has a bachelor’s degree in economics from the University of Vermont and a master’s degree in business from the University of Pennsylvania.

Thomas Finke will take over for Crandall both as chief investment officer and as chairman of MassMutual’s Babson Capital Management L.L.C. subsidiary, MassMutual says.

Glavin was president of Babson Capital before he became co-COO. He has a bachelor’s degree from the College of the Holy Cross.

Michael Fanning will succeed Glavin as executive vice president and head of MassMutual’s U.S. insurance group.