UPDATE 1-Glaxo ups emerging market drive with S.Korean deal

* To buy 9.9 percent of Dong-A for 73.9 million pounds

* Glaxo gets stake in South Korea’s leading drugmaker (Adds detail, background on emerging markets strategy)

LONDON, May 11 (Reuters) - GlaxoSmithKline GSK.L stepped up its drive into emerging markets on Tuesday by agreeing to buy a 9.9 percent stake in South Korea's Dong-A Pharmaceuticals 000640.KS for 73.9 million pounds ($114 million).

Emerging markets are the new battleground for the world’s top drugmakers as sales stall in Western markets.

The deal wins the British-based group an alliance with the leading pharmaceuticals and over-the-counter medicines company in South Korea -- a market expected to grow around 10 percent a year through 2012.

Glaxo chief executive Andrew Witty has already signed a string of deals to increase his company's footprint in key emerging markets, including taking a similar minority holding in South African Aspen Pharmacare APNJ.J.

The new alliance will initially co-promote selected Glaxo and Dong-A drugs for use in primary care, but the companies said that additional synergies would be explored.

Glaxo and Dong-A, which had sales last year of 414 million pounds, will share profit from the co-promoted products above pre-agreed baselines. A new business unit will be created within Dong-A to manage the collaboration. (Reporting by Ben Hirschler; Editing by Dan Lalor) ($1 = 0.6465 pound)