Both deals have been with companies controlled by Russian entrepreneur Vladislav Sviblov: Stanmix Holding and Bering Metals.
In May, Amur said a fair market value for Kun-Manie was $106 million-$131 million, though factors such as the project's location in Russia meant that shareholders should accept the $105 million. But the shareholders baulked at lengthy timeframes.
The company now says they should take the substantially lower $35 million or face running out of options.
"Should shareholders reject the sale of Kun-Manie, there are virtually no alternatives available to our advancing development of the project," Amur's CEO Robin Young said.
"This includes a sale to non-Russian entities or to the ever increasing list of Russian sanctioned mining companies, funding institutions and banks. The majority of international resource associated entities within Russia have or are also withdrawing from Russian activities and operations," he said.
The new share purchase agreement with Bering represents a premium of 119% to Amur's market capitalization of 3 August of £13.2 million (US$15.93 million) and 44% to the current Kun-Manie book value of $24.3 million as at December 31, Amur said.
If approved, the company also intends to pay a special dividend of 1.8p per share to shareholders.
The terms of the Stanmix deal were to see $15 million upon completion, $10 million within 12 months, $50 million within 48 months, and $30 million in ten annual installments beginning in 2027.
Amur said shareholders weren't happy that the payments extended over as many as 15 years, that there was no absolute guarantee that they'd be forthcoming, the initial payment was too low, and dividends were not identified.
The new Bering deal has just the one payment and dividends are to be paid within 90 days of completion.
"The Company does not foresee that another offer to purchase Kun-Manie would be forthcoming in the event that the current offer is rejected," Young said.
Shareholders are scheduled to vote at a general meeting on 24 August.
On 7 June, Amur announced the completion of its TEO project feasibility study results with regard to Kun-Manie which showed an NPV10% of $333 million and IRR of 15.6%.
The results indicated the mine should be scaled up to as much as 12.4 million ore tonnes per year for a 19-year open pit operation.
Amur's share price closed trading on August 5 at a four-month high of 1.27p.
In the weeks prior to Russia's largest scale invasion of Ukraine on 24 February, Amur's share price closed as high as 3.90p.