Synthesis and Resolution of Substituted [5]Carbohelicenes

Three types of racemic [5]­helicenyl acetates (1a, 2, and 3a) were synthesized. The synthesis of 2 was achieved by regioselective oxidation using o-iodoxybenzoic acid. The enzymatic kinetic resolution of 1a–3a was studied. The conversion with the highest rate and ee was obtained using 1a as the substrate and lipase Amano PS-IM as the enzyme. The two enantiomers of 1-[5]­helicenol 3b were separated using (1S)-10-camphorsulfonyl chloride as the chiral resolving agent.