TY - JOUR
T1 - Reinvestigation of the Absolute Configurations of Chiral β-Mercaptoalkanones Using Vibrational Circular Dichroism and 1H NMR Analysis
AU - Kiske, Christiane
AU - Nörenberg, Svenja
AU - Ecker, Miriam
AU - Ma, Xingyue
AU - Taniguchi, Tohru
AU - Monde, Kenji
AU - Eisenreich, Wolfgang
AU - Engel, Karl Heinz
N1 - Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/11/16
Y1 - 2016/11/16
N2 - The absolute configurations of chiral β-mercaptoalkanones were previously assigned on the basis of the 1H 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 1H 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.
AB - The absolute configurations of chiral β-mercaptoalkanones were previously assigned on the basis of the 1H 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 1H 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.
KW - 2-mercapto-4-alkanones
KW - 4-mercapto-2-alkanones
KW - H NMR spectroscopy
KW - VCD
KW - absolute configuration
KW - lipase
UR - http://www.scopus.com/inward/record.url?scp=84996486743&partnerID=8YFLogxK
U2 - 10.1021/acs.jafc.6b03670
DO - 10.1021/acs.jafc.6b03670
M3 - Article
C2 - 27779841
AN - SCOPUS:84996486743
SN - 0021-8561
VL - 64
SP - 8563
EP - 8571
JO - Journal of agricultural and food chemistry
JF - Journal of agricultural and food chemistry
IS - 45
ER -