Acid-catalyzed formation of 32,35-anhydrobacteriohopanetetrol from bacteriohopanetetrol

32,35-Anhydrobacteriohopanetetrol (anhydroBHT) is a functionalized hopanoid of unknown origin found recently in a wide range of sediments. Acidic treatment of cells of the bacterium Zymomonas mobilis and of bacteriohopanetetrol (BHT) led to the formation of anhydroBHTs in the form of an epimeric mixture. These laboratory experiments indicate that sedimentary anhydrobacteriohopanepolyols likely correspond to diagenetic transformation products of bacteriohopanepolyols formed by intramolecular acid catalyzed cyclization of the hopanoid side chain, rather than being biogenic products.