Green Chemistry Principle #8
Unnecessary derivatization (use of blocking groups, protection/deprotection, temporary modification of physical/chemical processes) should be minimized or avoided if possible, because such steps require additional reagents and can generate waste.
By Peter J. Dunn, Green Chemistry Lead, Pfizer
One of the key principles of green chemistry is to reduce the use of derivatives and protecting groups in the synthesis of target molecules. One of the best ways of doing this is the use of enzymes. Enzymes are so specific that they can often react with one site of the molecule and leave the rest of the molecule alone and hence protecting groups are often not required.
A great example of the use of enzymes to avoid protecting groups and clean up processes is the industrial synthesis of semi-synthetic antibiotics such as ampicillin and amoxicillin.
In the first industrial synthesis Penicillin G (R=H) is first protected as its silyl ester [R = Si(Me)3] then reacted with phosphorus pentachloride at -40oC to form the chlorimidate 1 subsequent hydrolysis gives the desired 6-APA from which semi-synthetic penicillins are manufactured.
This synthesis has been largely replaced by a newer enzymatic process using pen-acylase. This synthesis occurs in water at just above room temperature. The new synthesis has many advantages from a green perspective one of which is that the silyl protecting group is not required.
More than 10,000 metric tons of 6-APA is made every year and much of it by the greener enzymatic process so this is a fantastic example of Green Chemistry making a real difference.
Back to Green Chemistry Principle #7
Next to Green Chemistry Principle #9
Back to the 12 Principles of Green Chemistry