Former executive vice president of the Yukos oil company, Vasily Alexanyan, died in Moscow on Monday aged 39 of AIDS-caused complications, the Dozhd TV channel reported citing his relatives.
Alexanyan, charged with money-laundering, tax evasion and embezzlement, was diagnosed with HIV a few months after he was arrested in 2006. Shortly after, he contracted tuberculosis and went nearly blind. According to the prosecution, he embezzled property and shares from the oil companies Tomskneft and VNK.
Alexanyan was released from custody in December 2008 after posting bail of 50 million rubles ($1.6mn at current rates). The bail was returned after the court announced its decision to dismiss the case. Charges against him were dropped in 2010.
Critics in Russia and the West said his treatment in jail was "inhumane."
Legal proceedings launched against the now defunct oil company Yukos in 2003, seen by critics as politically motivated, resulted in the conviction of many executives and shareholders, including founder and CEO Mikhail Khodorkovsky.
Khodorkovsky was arrested in 2003 on tax evasion charges and sentenced to eight years in 2005. His sentence was extended in a second trial on separate charges earlier this year and he is now due for release in 2016.
Lawyers for Yukos, which once pumped out more oil than both Libya and Qatar, had said that the company was hounded out of business after its owner Khodorkovsky - then Russia's richest man - began funding the Russian opposition. The Kremlin has consistently denied the allegation.
The European Court of Human Rights ruled in September 2011 that the Russian authorities had violated the rights of Yukos, but rejected claims that the breakup of the oil giant was politically motivated.