Racemic 2-(2-trifluoromethyl)-1H-benzo[d]imidazol-1-yl)benzoic acid (TBBA) was synthesized in three steps from 1-fluoro-2-nitrobenzene. Target (P)-and (M)-TBBA atropisomers were stable with a racemization barrier above 30 kcal/mol. As a chiral derivatizing agent, TBBA showed much higher differences in chemical shifts (Δδ PM ) than the conventional Mosher's acid.
Axially
chiral trifluoromethylbenzimidazolylbenzoic acid (TBBA)
was used as a chiral derivatization agent for the assignment of the
absolute configuration of β-chiral primary alcohols. The structures
varied from simple aliphatic alcohols to complex cyclic systems and
highly substituted sugar derivatives. The NMR-based method was successfully implemented to evaluate 17 compounds
and displayed ΔδPM values higher than 0.1 ppm
in most cases, which makes TBBA superior to MTPA and MPA and comparable
to 9-AMA.
Axially chiral 2-(2-(trifluoromethyl)-1
H
-benzo[
d
]imidazole-1-yl)benzoic acid (TBBA)
was used as a chiral
derivatizing agent to evaluate the limits of absolute configuration
assignment for β-chiral aminoalcohols. Seven Boc-aminoalcohols
and eight variously
N
-substituted (
S
)-phenylglycinols were prepared, and their TBBA esters were analyzed
by NMR spectroscopy. Diverse substitution at the β-position
was employed to demonstrate the effect of structure on the general
conformational model and reliability of the absolute configuration
assignment. It was concluded that hydrogen bond formation and steric
hindrance were the main factors affecting the correct assignment for
Boc-aminoalcohols.
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