A theoretical investigation of endocyclic allylic carbon-centered radical formation in retinoic acid

We have carried out theoretical calculations that suggest that C4 carbon-centered radical formation in (E)- and (13Z)-retinoic acid, catalyzed by cytochromes P450 and PGH synthase, occur by a direct H-atom abstraction mechanism rather than an electron abstraction mechanism. In addition, our calculations indicate that C4 radical formation in the 13Z-isomer is thermochemically preferred compared with the all trans-isomer.