Enzymatic formation of an unnatural novel tetracyclic sesterterpene by β-amyrin synthase

A convergent synthesis provided a C 25 and a C 35 oxidopolyprene in which a farnesyl C 15 unit is connected in a head-to-head fashion to a geranyl C 10 or a geranylgeranyl C 20 unit. When incubated with recombinant β-amyrin synthase from Pisum sativum the C 25 oxidopolyprene was enzymatically converted to an unnatural novel tetracyclic sesterterpene, while the C 35 analogue did not afford any cyclization product.