The Moscow City Court will hear an appeal against the new jail term handed down to former Russian oil tycoon Mikhail Khodorkovsky and his business partner Platon Lebedev on May 17.
The appeal was lodged by lawyer Karina Moskalenko on December 31, the day the two men were told they would have to stay in jail until 2017.
Moskalenko argues there were procedural violations during the 20-month trial that was widely condemned as politically motivated.
Khodorkovsky and Lebedev were jailed for embezzlement and money-laundering.
The two men had been nearing the end of a separate eight-year sentence for fraud and tax evasion from their 2005 trial.
In February, a former aide to the Russian judge who extended the two men's jail sentences claimed he had been put under pressure.
Speaking to gazeta.ru, a widely read liberal news portal, Natalya Vasilyeva said Viktor Danilkin had been under "total control" from the Moscow City Court.
Danilkin denied the allegations, describing them as slander, but said he would not seek Vasilyeva's prosecution.
The trial was widely viewed as a political vendetta by Russia's powerful prime minister, Vladimir Putin, whom Khodorkovsky challenged by funding liberal opposition parties in the early 2000s.
Khodorkovsky and Lebedev have always maintained that the charges against them are trumped up.
MOSCOW, April 27 (RIA Novosti)
