Russian billionaire and club owner Dmitry Rybolovlev bought a total of 37 masterpieces worth two billion euros ($2.1 billion) through art dealer Yves Bouvier over the space of a decade.
But their relationship disintegrated last year after he accused Bouvier of inflating prices, rather than finding him the best price, and taking a commission.
Rybolovlev's lawyers say Bouvier pocketed “between $500 million and $1 billion” from the inflated prices.
On Thursday, the Monaco appeals court rejected Bouvier's request that the case be dismissed, and ruled he should face fraud and money-laundering charges.
The woman who introduced the two, Tania Rappo, Rybolovlev's translator and godmother to his youngest daughter, will also face prosecution for taking a commission on the sales, her lawyer confirmed.
“I have been betrayed,” Rybolovlev told Le Parisien in September.
“(Bouvier) made us believe he was negotiating the price in our interest… while today he claims he was negotiating for himself as a salesman.”
'I'm not crazy'
Rybolovlev's lawyers say he became aware of the problem over dinner in New York, when an art consultant told him he had overpaid by $15 million for a Modigliani painting.
In another twist, Bouvier was in September charged with handling stolen goods for selling two Picasso watercolours to Rybolovlev.
Picasso's daughter-in-law, Catherine Hutin-Blay, claims that 'Woman Arranging her Hair' and 'Spanish Woman with a Fan' were stolen from her collection and never approved for sale.
Rybolovlev handed them over to authorities, saying he was unaware they were stolen.
But Bouvier has maintained his innocence, saying he bought the watercolours, along with 58 drawings, from a trust in Liechtenstein that claimed to represent Hutin-Blay.
“I am not crazy,” he told the New York Times. “I'm not going to sell stolen art to someone who has bought two billion in art from me. He was my biggest client.”
Bouvier is not only an art dealer, but also one of the leading organisers of offshore storage facilities for wealthy collectors, shuttling masterpieces between high-tech storage facilities in low-tax countries such as Switzerland, Luxembourg and Singapore.
Rybolovlev, who made his fortune in the fertiliser business after the collapse of the Soviet Union, has an art collection to rival major museums, featuring works by artists like Van Gogh, Monet, Rodin, Matisse and da Vinci.