A Russian businessman who was married to Vladimir Putin’s daughter received an estimated $380m (£283m) stake in a Russian petrochemicals company for just $100, an investigation by Russia’s iStories investigative outlet has claimed. The investigation, published in collaboration with the the Organised Crime and Corruption Reporting Project (OCCRP), used a trove of leaked emails to shine new light on the closed circle of family and associates who surround the Russian president. According to the investigation, Kirill Shamalov, the son of a longtime friend of Putin’s, purchased the sizeable stake in the parent company of petrochemicals giant Sibur through an offshore company. The deal was inked just months after he married Katerina Tikhonova, a scientist and university official who is widely reported to be Putin’s younger daughter. “It’s simple,” wrote Alexey Navalny, an opposition politician and anti-corruption activist. “Putin’s daughter gets married and the newlyweds receive the present of $380m.” The pair also reportedly spent millions of dollars buying and furnishing elite real estate near Putin’s residence in Russia and in Biarritz, France, the emails showed, purchasing a nearly £50,000 carpet and £5,700 in Japanese books. It was a life of luxury that, like Putin’s daughters, has been hidden almost entirely from public view. The emails, which were provided to the investigative journalists by an anonymous source (possibly hacked, they noted), also revealed an ascendant circle of young power-players from St Petersburg, who generally were the children and grandchildren of Putin and his friends and colleagues in government. The Guardian has approached Shamalov’s company, Ladoga Management, for comment. A representative took a reporter’s contact information but would not reply to specific questions. Shamalov had estimated Sibur’s value at $10bn in an interview with Kommersant, bringing his share to $380m, according to his valuation. In emailed remarks, a Sibur representative confirmed to the Guardian that Shamalov had acquired shares in the company under a stock-option plan for managers but did not confirm the price. In a statement, Dmitry Konov, the head of the company’s board of directors, said: “The conditions for the sale of the shares in the deal were no different from those for a number of other managers, there were no exclusive conditions for KN Shamalov.” “The company is ready to document these circumstances with the engagement of independent experts [from outside the company,]” a company statement said. The leaked emails, some of which iStories and OCCRP said they had verified with Shamalov’s interlocutors, are a rare, documented look at how those in Putin’s circle manage to acquire fantastic wealth. Multiple companies, including telecommunications and developers, sought to bring Shamalov in as an investor after his marriage to Tikhonova. Several Russian outlets have released exposes recently looking at the Russian leader’s family and also his romantic life. Another article earlier this month suggested that Putin had fathered a daughter with a woman who had later been named a shareholder to one of Russia’s most important banks, making the former cleaner an overnight millionaire. Another showed that a former Olympic gymnast rumoured to have been Putin’s girlfriend had received an annual salary of £7.7m as the head of a pro-Kremlin media group. In all cases, the Kremlin has sought to sidestep the bad press. “We still refrain from commenting on such publications,” said Dmitri Peskov, a Putin spokesman, when asked about the articles on Monday. “These rumours often have nothing to do with reality.”