Here, several attempts with different isomers were performed for the O-O-cleavage of 4b. Note that the structure resulting from the previous reaction 3b→4b was extended by a proton on His147 and re-optimized to use the His147 for hydrogen transfer again. However, the O-O-cleavage was not possible for any of the linear transits, or relaxed optimizations (Fig. ). The O-O-cleavage after the second reduction also turned out to be unfavorable.