London giant Allen & Overy (A&O) has won the role of advising Dutch chemicals maker DSM on the 2.25bn (£1.41bn) acquisition of the vitamins business of Swiss biotech giant, Roche Holdings.

The deal is being led by A&O’s Dutch practice through corporate partner Maarten Muller. Amsterdam-based partner Ian Powell is handling the finance side with UBS Warburg acting as financial advisers.