The new way to make the drug devised by Elias Corey of Harvard University in the United States, who won a Nobel Prize for chemical synthesis in 1990, and his colleagues, is to use two cheap and plentiful petrochemicals -- acrylate and butadiene, according to a fresh report on the website of New Scientist.

Corey said his novel catalyst, made from amino acid proline, which links those chemicals in the basic six-carbon-molecule backbone of Tamiflu, produces the correct form and the full production process involves two more new processes, including "a brand new reaction" using another novel catalyst, brominated tin.

"It can all be done at room temperature, except one step that needs refrigeration," said Corey, adding the technique produces high yields.

At present, Tamiflu is made mainly by the Swiss firm Roche, starting with a molecule called shikimic acid, either taken from the Chinese spice star anise, or made with genetically engineered bacteria.

Tamiflu is the biggest hope for saving people at the start of abird flu pandemic, before a vaccine is available, but is hard to make and stocks are limited.

Making Tamiflu is slow, partly because shikimic is hard to get, but also because one step in the process involves a highly explosive chemical called an azide. As a result, Tamiflu can be made only in small batches of a few tens of liters at a time.

As demand for Tamiflu has skyrocketed over fears of a flu pandemic, Roche has vastly increased production capacity. It will be able to make 400 million courses of treatment by the end of this year. But even then it will take years to make the emergency stockpiles countries like Britain have ordered.