Kiske Christiane, Nörenberg Svenja, Ecker Miriam, Ma Xingyue, Taniguchi Tohru, Monde Kenji, Eisenreich Wolfgang, Engel Karl-Heinz
Lehrstuhl für Allgemeine Lebensmitteltechnologie, Technische Universität München , Maximus-von-Imhof-Forum 2, D-85354 Freising-Weihenstephan, Germany.
Frontier Research Center for Post-Genome Science and Technology, Faculty of Advanced Life Science, Hokkaido University , Kita 21 Nishi 11, Sapporo 001-0021, Japan.
J Agric Food Chem. 2016 Nov 16;64(45):8563-8571. doi: 10.1021/acs.jafc.6b03670. Epub 2016 Nov 3.
The absolute configurations of chiral β-mercaptoalkanones were previously assigned on the basis of the H NMR anisotropy method using (S)-2-methoxy-2-(1-naphthyl)propionic acid ((S)-MαNP) as the chiral auxiliary. This study presents a reinvestigation of the configurations of 4-mercapto-2-pentanone 1, 4-mercapto-2-heptanone 2, and 2-mercapto-4-heptanone 3. Enantiomers of 1, 2, and 3 were obtained by lipase-catalyzed hydrolyses of the respective acetylthioalkanones. Upon derivatization with (S)-MαNP, the configurations of the reaction products were deduced based on the order of the HPLC elution of the diastereoisomeric thioesters, assuming that the sector rule previously developed for secondary alcohols is also valid for thiols. In addition, the configurations were experimentally determined by vibrational circular dichroism (VCD) and H NMR analyses after esterification with (R)-hydratropic acid (HTA) and 2-methoxy-2-phenylacetic acid (MPA). The assignments of the configurations using VCD and NMR analyses of HTA- and MPA-thioesters were in agreement. However, they were opposite to those deduced for (S)-MαNP thioesters via the sector rule. Consequently, the formerly assigned configurations of β-mercaptoalkanones deduced via investigation of (S)-MαNP-derivatives have to be revised.
