How the mighty have fallen. Once top of the tree in the boom years, Russia’s top oligarchs are under increasing pressure by both the Kremlin and the shrinking economy and starting to sell their assets.

Russian billionaire Viktor Vekselberg, still flush from the billions he earned when he sold out his stake in oil company TNK-BP to state-owned oil giant Rosneft, is now considering the purchase of fellow oligarch Mikhail Prokhorov's Onexim's stake in major aluminum producer Rusal, he said on the sidelines of the Vladivostok Economic Forum, Rambler News Service (RNS) reported on September 2.

"We are negotiating," he was quoted as saying, without providing any more detail.

According to other unnamed sources, Vekselberg's Renova group is negotiating the purchase of Onexim's 17.02% share in Rusal for $1bn, which is $200mn more than an offer from billionaire Suleiman Kerimov’s son, Said, RNS reported.

Prokhorov obtained his share in Rusal is the world's largest aluminum producer outside China, back in 2008, in exchange for his stake in Norilsk Nickel. The increasingly embattled Prokhorov has been shedding his assets in Russian commodity companies, selling his 20%-stake in potash miner Uralkali two months ago. He is also said to be in talks with Chinese firm Fosun International over the possible sale of a stake in his Russian investment bank Renaissance Capital, Russian media reported in mid-August.

The deal, if closed, would be another sign that the private oligarch’s halcyon days are over. Prokhorov was one of a new generation of oligarchs to emerge after the 2008 crisis as a top Russian business dog. He sold much of his holding in Norilsk Nickel in the boom years and was largely in cash when the 2008 global meltdown hit.

He was also in the Kremlin’s good books as part of its ZAO Kremlin informal management of the economy where captains of industry met with Putin who gave them “advice” on where to invest their money.

Prokhorov picked up his stake in Rusal by bailing out Oleg Deripaska, another top oligarch and member of ZAO Kremlin, who had leveraged himself to the hilt on soft state loans to build a metals empire. Onexim owned a 17% stake in Rusal but bought more by buying up the struggling company’s debt.

The deal may also be a settling of scores as Prokhorov and fellow billionaire and stakeholder Vekselberg have clashed with Deripaska over his decision keep a 25% share in Norilsk Nickel, a company whose value has dropped with falling precious metal prices and increased production costs.

Prior to the crisis Deripaska’s Rusal bought a blocking stake in Norilsk Nickel from Prokhorov for a reported $7bn as part of a grand Kremlin-backed plan to set up a global metals and mining giant to rival BHP Biliton. As part of the deal Prokhorov got 14% in Rusal. At the time, Deripaska was Russia’s richest man. Today he doesn't feature in the top 10, but is still thought to be worth $3bn according to Forbes.