A raft of US law firms have won roles on Microsoft's $8.5bn (£5.2bn) acquisition of Skype Global, the internet voice and video chat service, reports The Am Law Daily.

The all-cash deal – Microsoft's largest acquisition ever – will give the software giant a leading communications brand to partner with its other products such as Outlook, Lync, and Xbox LIVE.

Microsoft turned to Covington & Burling, Cadwalader Wickersham & Taft and Simpson Thacher & Bartlett for advice on the deal.

Simpson Thacher's team is led by corporate partners Charles Cogut and Alan Klein, as well as compensation and benefits partner Gregory Grogan, while Cadwalader is providing antitrust advice with a team led by partners Rick Rule and Jonathan Kanter.

San Francisco intellectual property partners Evan Cox and Bruce Deming are heading up the Covington team that also comprises lawyers in Brussels, London, and Washington DC. Microsoft's general counsel, Brad Smith, is a former Covington partner.

Meanwhile, Sullivan & Cromwell is advising Skype and private equity firm Silver Lake Partners, which holds a controlling interest in the company, fielding a corporate team led by London partner Richard Morrissey, Los Angeles partner Alison Ressler and Palo Alto partner Sarah Payne.

Skadden Arps Slate Meagher & Flom is advising Skype founders Niklas Zennstroem and Janus Friis, as well as their company Joltid, which is also a Skype shareholder.

The deal, which has been approved by the boards of both Microsoft and Skype, is expected to close by the end of the year.

The Am Law Daily is a US affiliate title of Legal Week.