Peter Dunn is the global green chemistry leader at Pfizer Inc. Sandwich, UK.   He has worked for Pfizer since 1989, and has invented the processes to make four drugs, including Viagra (sildenafil) and Emselex (darifenacin). He is also a member of the Green Chemistry Editorial Board

Who or what inspired you to be a scientist?

I left school at 16 and worked on pharmaceutical intermediates for anti-ulcer drugs for 7 years at Robertson Brothers Ltd in West Bromwich, UK during which time I completed a part time degree. Then I went to do a PhD with Charles Rees and it was him who really inspired my interest in chemistry. He was a wonderful teacher and mentor and had an infectious enthusiasm for chemistry. He was one of those people that could have been anything, even a politician or comedian. He was a great character and so multi-talented. He was a fantastic scientist!  

Why is finding green methods of importance to an international pharmaceutical company? 

Pfizer is interested in green chemistry for three reasons: (i) to deliver medicines to patients with limited impact on the environment (ii) to deliver cost savings that are much needed by the company (iii) we feel that green chemistry is the right thing to do for our business and for our communities

Why is green chemistry important to you?  
I have always been interested in environmental matters and using the Earth's resources sparingly. I grew during the 1970s and the oil crisis. Back then we were worried about the oil running out whereas now we are more worried about the CO₂ emissions from fossil fuels. When I worked on Viagra, several people at Pfizer encouraged me to develop a really efficient synthesis with low environmental impact. As Viagra was a high profile medicine I was then fortunate to be invited to green chemistry conferences to talk about the project and my interest in green chemistry snowballed from there.

How do you promote the importance of green chemistry within Pfizer Inc? 
Within Pfizer we have green chemistry teams set up at each of our small molecule research sites. These teams promote green chemistry at their site and set local improvement goals. We also have strong links with our manufacturing division.  

A big part of green chemistry is recognition for the outstanding work done by Pfizer scientists so we set up three Global Green Chemistry Awards in 2002. One is for small molecule research, one for our manufacturing division and   the other for our large molecule scientists. The winners receive £3000 which they donate to an environmental charity of their choice or an academic research group.   I'm always blown away by the fantastic achievements of our award winners.

In terms of our outreach outside of the company we sponsor green chemistry education within schools including free lesson plans available on the internet. We also organise green chemistry workshops for students in the US, Ireland, Puerto-Rico and the UK and we sponsor a number of green chemistry projects in academia.

What are the main challenges facing green chemistry researchers at present? 
I published a paper with scientists from other pharmaceutical companies outlining   twelve key green chemistry research areas for the pharmaceutical industry in green chemistry. Personally, I am particularly concerned that many rare metals such as rhodium and iridium are being used up at an alarming rate. So I think new methodology which replaces rare metal catalysis with more abundant metal catalysis or even better biocatalysis are of great value.

What achievement are you most proud of?
I was very proud to lead the Viagra process development team all the way from the initial drug discovery to the point where the compound was approved and on the market.

The original molecule was synthesised for angina, but the trials were not very successful. The company then moved into research on male erectile dysfunction and the molecule was approved for treating this in 1998 with the trade name Viagra. The molecule was also found to be very good at treating pulmonary hypertension - a disease where there is increased pressure in the pulmonary arteries affecting mostly women, but can also affect men. The disease can lead to shortness of breath, tiredness, chest pain, and a racing heartbeat. It was therefore interesting that the same drug could be used for both men and women but for different reasons. Revatio is the trade name for the same drug, but for treating pulmonary hypertension.

The program was accelerated by the company then accelerated again so we were very pleased to develop very efficient, environmentally friendly chemistry within the tight timelines. That synthesis is still used today so it has stood the test of time.

If you weren't a scientist, what would you be?
If I weren't a scientist, I would have liked to be a musician in an orchestra or backing group. My sister is a musician and we both have a love of music.