Crenarchaeol is considered an ‘iconic molecule’ in organic geochemistry. Although a challenge of stature, it did not let organic chemist Adri Minnaard go and this year his PhD student Mira Holzheimer almost managed to synthesise it. 

‘Do not fall into the trap of usefulness’, Adri Minnaard, an organic chemist and director of the Stratingh Institute for Chemistry at the University of Groningen, told me. ‘Presumably, crenarchaeol makes the membrane less permeable, which is only important for life under more extreme conditions. The molecule will not become a medicine, not a material, and if you want to use crenarchaeol, it is ultimately better to isolate it from sediment than to make it chemically. The main question of our research was whether molecules of this complexity could be made by chemists.’ 

Because it is indeed complex: crenarchaeol consists of a ring of 66 atoms, 22 chiral centres, 4 five-membered rings and a six-membered ring. If such a molecule would occur in nature, then surely in minuscule quantities and in an exotic organism? ‘Wrong’, Minnaard says. ‘We see the molecule in archaea of the genus thaumarchaeota: single-celled organisms that you find in every litre of seawater. And given the amount of seawater on earth, plus the gigantic amount of sediment in which this molecule is preserved, this means that the molecule must be one of the most common complex organic substances on earth.’