Chiral sulfinates studied by optical rotation, ECD and VCD: the absolute configuration of a cruciferous phytoalexin brassicanal C

The optical rotation, electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) of chiral sulfinates have been studied experimentally, and analysed by density functional theory calculation, aiming at establishing a reliable and convenient methodology to determine their absolute configuration. Through the study on a model chiral sulfinate with known absolute configuration, (R)-(+)-methyl p-toluenesulfinate ((R)-(+)-1), each technique was found to be reliable in assigning chirality of sulfinates. We then applied these methods to a synthetically prepared cruciferous phytoalexin, brassicanal C ((-)-2), and unambiguously determined its absolute configuration as S. The advantages and disadvantages of each spectroscopy on sulfinates are also discussed.