Simpson Thacher & Bartlett LLP and Sullivan & Cromwell LLP engaged in a little role reversal on Microsoft Corp.'s $8.5 billion agreement to buy Skype Technologies SA, announced May 10.

S&C has a very long relationship with Microsoft, but Simpson Thacher's Charles "Casey" Cogut and Alan Klein advised the Redmond, Wash.-based software giant on the M&A aspects of the Skype deal. And while Simpson has deep ties to Silver Lake, which led a consortium that bought 70% of Skype from eBay Inc. in 2009 and still controls the Internet phone service provider, Sullivan & Cromwell's Richard Morrissey, Alison Ressler and Sarah Payne are representing Silver Lake and Skype on the Microsoft deal.

Cogut and Klein represented Microsoft when it made a $45 billion hostile bid for Yahoo! Inc. in 2008, but Simpson Thacher had to bow out of the matter because of a client conflict. So Sullivan & Cromwell's James Morphy, Alexandra Korry, Eric Krautheimer and Duncan McCurrach took over the assignment. Microsoft ended up dropping the bid and has been quiet on the acquisitions front since then.

While Simpson Thacher is handling the corporate work on the Skype acquisition, Microsoft tapped a Covington & Burling LLP team led by Evan Cox and Bruce Deming for advice on intellectual property, telecommunications, data privacy, antitrust and patent issues. Microsoft general counsel Brad Smith was a partner at Covington before joining the software giant in 1993. Microsoft is also using Charles "Rick" Rule and Jonathan Kanter of Cadwalader, Wickersham & Taft LLP for antitrust advice.

Microsoft tapped Bear Stearns Cos., Blackstone Group LP and Morgan Stanley on the Yahoo! bid but is going without a banker on the Skype deal. That's highly atypical in such a large transaction but not unprecedented; IBM Corp., for example, tends to be sparing in its use of bankers.

For its part, Sullivan has done work for Silver Lake's London office since Egon Durban opened it in 2005 and represented the private equity firm when it bought Skype in 2009. Sam Britton and Nick Giovanni of Goldman, Sachs & Co. along with J.P. Morgan are representing Skype and Silver Lake on the Microsoft deal.

Skype founders Niklas ­Zennström and Janus Friis turned to Michael Gisser and Rick Madden of Skadden, Arps, Slate, Meagher & Flom LLP. -- David Marcus

Hertz Global Holdings Inc. added Cravath, Swaine & Moore LLP to its advisers team when the car rental company renewed its bid for Dollar Thrifty Automotive Group Inc. on May 9. In April, Hertz turned to Debevoise & Plimpton LLP's John Allen and Jonathan Levitsky and Jones Day antitrust partners Joe Sims and Michael Knight for advice on a $1.2 billion cash-and-stock bid worth $41 per share. In September, Avis Budget Group Inc. bid $47 in cash and stock for Dollar Thrifty. Hertz raised its bid to $51 a share, but Avis countered with $53.50 a share, and Dollar Thrifty shareholders rejected the Hertz deal in September.

But antitrust regulators at the Federal Trade Commission have been slow to approve Avis' offer, and as Hertz was considering whether to take another run at Dollar this winter, the once and future bidder decided that adding another law firm might be helpful. It contacted Cravath's Scott Barshay, about whose work Hertz general counsel J. Jeffrey Zimmerman had heard.

Barshay and Cravath partner Minh Van Ngo are working with Allen, Levitsky and Knight on the new bid. Debevoise is the regular counsel to Clayton, Dubilier & Rice LLC, which led a consortium of private equity firms that paid $14.3 billion for Hertz in 2005.

Hertz used Barclays Capital, Bank of America Merrill Lynch and Deutsche Bank Securities Inc. for banking advice on the initial bid and supplemented that squad with Lazard's Mark McMaster for the second go-round. -- D.M.

When Dublin-based Elan Corp. plc agreed to sell its drug technologies unit to Alkermes Inc. for $961 million, it looked for financial advice from one of the largest U.S. investment banks, Citigroup Inc., and a young but growing international financial advisory firm, London-based Ondra Partners LP.

Neither choice was a surprise. Citigroup, whose Elan team was led by Chris Hite and Bill White, advised Elan when it sold a $1 billion stake to Johnson & Johnson in 2009. Ondra worked for Elan on that deal and has called the company a client since its founding three years ago by the former head of Lehman Brothers Holdings Inc.'s U.K. investment bank, Michael Tory.

Tory and partner Michael Baldock led a team including Larry Codraro, Jordon Giancoli and Michiel Broker that helped develop a large cash-and-stock deal structure for the sale of Elan Drug Technologies, announced May 9. The structure worked almost like a merger, with the parent securing a 25% stake in Alkermes and Alkermes relocating from Cambridge, Mass., to Dublin.

"They had two sets of advisers they had trusted and used," says Baldock, who is based in Stamford, Conn. In addition to its work for Elan, Ondra also had a relationship with Alkermes. "It made it a much easier situation."

Ondra advised on a similar deal structure this year when Henderson Group plc announced in January it would acquire Gartmore Group Ltd. for $522.6 million. That deal, which UBS also worked on, left Gartmore investors with a 22.5% stake in Henderson. Other deals for Ondra include advising GDF Suez SA on its buyout of the 70% it didn't own in International Power plc for $2.2 billion in 2010. "I think we've been very lucky, very fortunate to have a growing number of clients with trusting relationships," Baldock says.

Elan took legal advice from a team led by Christopher Cox, an M&A partner at Cahill Gordon & Reindel LLP. Cahill also worked on Elan's deal with Johnson & Johnson. John Given and Cian McCourt from A&L Goodbody Solicitors provided legal advice from Dublin.

Alkermes sought financial advice from a Morgan Stanley team of Jessica Chutter, Steven Harr, Susan Huang, Ari Terry and Whit Marshall. Its legal advisers included a Cleary Gottlieb Steen & Hamilton LLP team led by partners Daniel Sternberg, Jorge Juantorena and William Groll, along with a team led by Stephen Hegarty and Christopher McLaughlin, corporate partners at Arthur Cox in Dublin. -- David Holley

James Griffin was thrown into the dealmaking fray immediately after he joined the Palo Alto, Calif., office of Dewey & LeBoeuf LLP last month from Fulbright & Jaworski LLP in Dallas. Griffin and Dewey & LeBoeuf's Keith Flaum teamed up to represent Applied Materials Inc. on its $4.9 billion agreement to buy Varian Semiconductor Equipment Associates Inc., announced May 4. The Varian deal was the first signed transaction that Griffin's worked on since joining Dewey & LeBoeuf.

Griffin got to know Flaum and Dewey & LeBoeuf M&A partner Rick Climan through the American Bar Association's M&A committee, which Climan at one point chaired. They led a group of lawyers who moved to Dewey & LeBoeuf from Cooley LLP two years ago, and Climan began lobbying Griffin to make the move to Palo Alto.

While Griffin is new to the Valley, Flaum has represented Santa Clara, Calif.-based Applied Materials for more than a decade. As a partner at Cooley, Flaum represented the company on many deals including its $1.8 billion purchase of Etec Systems Inc. in 2000 and its $464 million purchase of Applied Films Corp. in 2006. After joining Dewey & LeBoeuf, in November 2009 Flaum counseled Applied Materials on its $364 million purchase of Semitool Inc.

For banking advice on all of those deals, Applied Materials used Morgan Stanley, whose Nicholas Osborne led the team on the Varian buy.

Gloucester, Mass.-based Varian used Boon Sim, global head of M&A at Credit Suisse Group, and Gary Horowitz and Marni Lerner at Simpson Thacher & Bartlett LLP for advice. -- D.M.