An 89-year-old heir to a famous fortune was headed for a prison Friday after years of fighting his conviction on charges of plundering millions of dollars from his socialite philanthropist mother, Brooke Astor.

A judge ordered Anthony Marshall to start serving his 1- to 3-year term. Marshall was sentenced in 2009 but had been free on bail during an appeal. He lost a series of requests to get a new trial and to stay out of prison because of his failing health.

"I take no pleasure in following my duties," said Manhattan state Supreme Court Justice A. Kirke Bartley, who had sentenced Marshall to the minimum for his conviction.

Astor was a fixture of New York society before she died in 2007 at 105, and her charitable largesse was recognized in 1998 with the Presidential Medal of Freedom, the nation's top civilian honor.

The judge read parts of a letter from one of Marshall's sons, Alex, urging the court to spare him prison.

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Prosecutors said Marshall, a former U.S. ambassador, exploited his mother's failing mind to loot her millions.

After she was diagnosed with Alzheimer's, he bought himself pricey gifts, including a $920,000 yacht, with her money. He also engineered changes to her will that gave him control of most of her estate, the district attorney's office said.

-- AP