While there are natural products now known which are bigger and therefore arguably more complex, their biosynthesis appears to be relatively straightforward in terms of the chemistry involved. For vitamin B12, on the other hand, the chemistry involved appeared at the outset to be anything but straightforward and certain to involve reactions and intermediates which were completely new to both synthetic and enzymic chemistry. The biosynthesis of B12 has therefore been described as the Everest of biosynthetic problems. In this chapter we will describe the complete pathway that has now been elucidated for the aerobic organism, Pseudomonas denitrificans. It does indeed involve much fascinating, novel and totally unexpected chemistry.
Department of Chemistry
University of Cambridge