FURTHER EVIDENCE THAT THE POLYCYCLIZATION REACTION BY OXIDOSQUALENE-LANOSTEROL CYCLASE PROCEEDS VIA A RING EXPANSION OF THE 5-MEMBERED C-RING FORMED BY MARKOVNIKOV CLOSURE - ON THE ENZYMATIC PRODUCTS OF THE OXIDOSQUALENE ANALOG HAVING AN ETHYL RESIDUE AT THE 15-POSITION

The incubation of the substrate analogue, (3S)-(6E,10E, 14E,18E)- rame thyl-2,3-epoxytetracosa-6,10,14,18,22-pentaene (-)-1 with 2,3-oxidosqu alene-lanosterol cyclase from pig liver gave products 2 (a lanosterol homologue) and 3 (a tricyclic product), definitively demonstrating tha t the cyclization of oxidosqualene proceeds via the expansion reaction from a 5- to a 6-membered ring for the C-ring formation of lanosterol .