4. Ranbaxy-Daiichi Sankyo: $4.5 billion

Marking the largest-ever deal in the Indian pharma industry, Japanese drug firm Daiichi Sankyo in June 2008 acquired the majority stake of more than 50 per cent in domestic major Ranbaxy for over Rs 15,000 crore ($4.5 billion).

The deal created the 15th biggest drugmaker globally, and is India's 4^th largest M&A deal to date.