Determination of optical purity and absolute configuration of natural 12‐hydroxystearic acid by the ¹H NMR anisotropy method

Abstract

The enantiopure of (R)-(-) MaNPA was allowed to react with racemic 18-(tert-butyldimethylsilyloxy)-5-octadecayne-7-ol which was derived from dodecane-1,12-diol, yielding diastereomeric esters mixture. These racemic esters were easily separated by HPLC on silica-gel. The absolute configurations of the first-eluted diastereomeric esters from the separated esters were determined using 1 H NMR anisotropy method. Analysis on 1 H NMR spectra and HPLC elution time of the synthesized esters and those of MaNP ester derived from natural methyl-12-hydroxystealate showed that the absolute configuration of natural 12-hydroxystearic acid was R form, and the enantiomeric excess was over 99%.

Configurational Assignment of ‘Cryptochiral’ 10‐Hydroxystearic Acid Through an Asymmetric Catalytic Synthesis

“…Ricinoleic acid ( 2 ) is the foremost acyl component in castor oil, and thus 12‐( R )‐hydroxystearic acid (12‐HSA; 3 ) in hydrogenated castor oil ( Fig. ) . Other hydroxylated fatty acids result from hydration by bioconversion of various unsaturated precursors.…”

“… For an alternative approach to determining the absolute configuration of hydroxy‐fattyacids via anisotropical chemical shift analysis of suitable derivatives as applied to 12‐hydroxystearic acid, [see Ref. ]; application of the modified Mosher method[21] to the configuration determination of 12‐ and 13‐hydroxystearic acids has been reported,[22] but relies on the single chemical shift difference of the terminal CH 3 group of the hydrocarbon branch of the secondary alcohol, whereas it is recommended to list Δδ values of several corresponding protons in both branches for assigning absolute configuration with a higher degree of certainty. [21b] …”

Chirality-Controlled Syntheses of Double-Helical Au Nanowires

“…Chiral d -12-hydroxystearic acid (D-HSA, Figure ) was used as the organogelator that introduces chirality into the structure of the soft-template because D-HSA self-assembles to form ribbon-like nanostructures with a right-handed twist . D-HSA is a well-known organogelator used in commercial products, and enantiopure D-HSA is easily obtained in large quantities by the hydrogenation and hydrolysis of castor oil . Furthermore, L-HSA (Figure ), with the opposite chirality to D-HSA, forms left-handed twisted nanoribbons, and can be synthesized through the chiral inversion of D-HSA (Scheme S1).…”