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

Abstract

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.

Chiral Induction from Allenes into Twisted 1,1,4,4‐Tetracyanobuta‐1,3‐dienes (TCBDs): Conformational Assignment by Circular Dichroism Spectroscopy

“…The slight blue-shift of the predicted CD bands relative to the observed CD bands, has been reported in other DFT-based studies. [12] All features of the experimental spectrum are qualitatively well reproduced by the calculations (Figure 5).…”

Recent advances in the use of vibrational chiroptical spectroscopic methods for stereochemical characterization of natural products

“…163 These assignments were also supported by ECD analysis. 164 Many chromones and furanones have also been investigated using VOA methods. 164 Many chromones and furanones have also been investigated using VOA methods.…”

“…171 Klaivanolide (158), an antiparasitic compound isolated from Uvaria klaineana, was originally assigned as a seven-membered lactone whose absolute conguration was determined as (+)-(S) using VCD and DFT (B3LYP/TZ2P). The great importance of including solvent effects in quantum chemical calculations of OR, ECD, and VCD was demonstrated using (+)-(2S,3S)-garcinia acid dimethyl ester (164). Klaivanolide is actually the known molecule acetylmelodorinol (159).…”

Progress in the Chemistry of Organic Natural Products 100

“…(b) Omit maps through the atoms of water molecule W1. The two H or D atoms have been omitted for the phase calculation (253) Structure Elucidation of Natural Compounds by X-Ray Crystallography Pyrococcus furiosus rubredoxin (283), urate oxidase (284), gamma-chymotrypsin (285), thaumatin (286), and sulfite reductase D (287).…”

“…With the aim of establishing a confident chiroptical method to establish the absolute configuration of sulfur-containing cruciferous phytoalexins, the VCD methodology was applied to (+)-(R)-methyl p-toluenesulfinate (217), a model sulfinate of known stereochemistry, and to a synthetically prepared cruciferous phytoalexin, (-)-brassicanal C (218), of natural origin (286). Phytoalexins are antimicrobial secondary metabolites produced de novo after their exposure to physical, biological or chemical stress as exemplified by plants of the family Cruciferae, which include important vegetable crops inclusive of cabbage, broccoli, cauliflower, and mustard.…”