Marshall, a decorated veteran who was a Broadway producer and U.S. diplomat, arrived in a wheelchair pushed by his wife Charlene. Marshall and his co-defendant, former estates lawyer Francis Morrissey, 72, were convicted in 2009 of looting the estate of Brooke Astor, whose fortune was estimated to be worth around $200 million. She died in 2007 at the age of 105. Morrissey began serving his sentence on Thursday. Under Astor's will, her only child, Marshall, stood to inherit tens of millions of dollars. After he was convicted of grand larceny, fraud and other charges, he received a settlement of $14.4 million. The rest of the money went to charity. The State Parole Board approved Mr. Marshall’s request for medical parole, ruling that he was so sick and frail as to be eligible for release under the state’s so-called compassionate release law. Mr. Marshall was born Anthony Dryden Kuser in New York City on May 30, 1924, the son of Mrs. Astor’s first husband, John Dryden Kuser, a New Jersey politician. His parents were divorced and the boy, called Tony, took the surname of his mother’s second husband, Charles H. Marshall, a stockbroker. He attended Brooks School in North Andover, Mass. In World War II, he became a Marine officer and was wounded at Iwo Jima. He received a bachelor’s degree at Brown University in 1950. He worked for the C.I.A. from 1954 to 1957, helping, by his own account, to develop the U-2 spy plane. He was the United States consul in Istanbul in 1958-59 and held a series of ambassadorships — to the Malagasy Republic (1969-71), Trinidad and Tobago (1972-73), Kenya (1973-77) and the Seychelles (1976-77). He was on the boards of many educational, cultural and philanthropic organizations, including the Vincent Astor Foundation, which closed when the last of its assets were given away. Mr. Marshall was married three times. His first two marriages were to Elizabeth Cynthia Cryan, in 1947, with whom he had the twin sons, Alexander and Philip, and to Thelma Hoegnell, in 1962. Both ended in divorce. In 1992, he married Charlene T. Gilbert. Besides his wife and his twin sons, Mr. Marshall is survived by three grandchildren; his wife’s three children by a previous marriage, Robert Gilbert, Inness Hancock and Arden Delacey; and three stepgrandchildren.