TY - JOUR
T1 - Preparation and absolute configuration of (1R,4R)-(+)-3-oxo-, (1S,4S)-(-)-3-oxo- and (1R,3S,4R)-(+)-3-acetyloxy-5-oxo-1,8-cineole
AU - Loandos, María Del H.
AU - Villecco, Margarita B.
AU - Burgueño-Tapia, Eleuterio
AU - Joseph-Nathan, Pedro
AU - Catalán, César A.N.
PY - 2009
Y1 - 2009
N2 - Enantiomerically pure (1S,4S)-(-)-3-oxo-1,8-cineole (-)-2 and (1R,4R)-(+)-3-oxo-1,8-cineole (+)-2 were prepared for the first time and their absolute configurations assigned by vibrational circular dichroism (VCD) measurements. Thus, treatment of cineole 1 with chromyl acetate gave rac-2 which after sodium borohydride reduction and acetylation provided racemic 3-endo-acetyloxy-1,8-cineole, rac-4. Enantioselective hydrolysis using porcine liver esterase (PLE) gave a mixture of 3-endo-hydroxy-1,8-cineole (-)-3 and 3-endo-acetyloxy-1,8-cineole (+)-4. After chromatographic separation, (-)-3 was oxidized to (+)-2, while (+)-4 was hydrolysed to (+)-3 and then oxidized to (-)-2. The absolute configuration of either ketone 2 was established by VCD spectroscopy in combination with density functional theory (DFT) calculations at the B3LYP/DGDZVP level of theory, from where it followed that the (+)-2 enantiomer corresponds to (1R,4R)-1,3,3-trimethyl-5-oxo-2-oxabicyclo[2.2.2] octane and the (-)-2 enantiomer to the (1S,4S) molecule which is also in agreement with the absolute configuration deduced by the Mosher method for the starting chiral alcohols. Some literature inconsistencies are clarified. In addition, the enantiomerically pure monoester (1S,3S,4R,5R)-(-)-3-acetyloxy-5- hydroxy-1,8-cineole 6 and the ketoester (1R,3S,4R)-(+)-3-acetyloxy-5-oxo-1,8- cineole 7 were prepared from meso-diacetate 5 by enantioselective asymmetrization also using PLE.
AB - Enantiomerically pure (1S,4S)-(-)-3-oxo-1,8-cineole (-)-2 and (1R,4R)-(+)-3-oxo-1,8-cineole (+)-2 were prepared for the first time and their absolute configurations assigned by vibrational circular dichroism (VCD) measurements. Thus, treatment of cineole 1 with chromyl acetate gave rac-2 which after sodium borohydride reduction and acetylation provided racemic 3-endo-acetyloxy-1,8-cineole, rac-4. Enantioselective hydrolysis using porcine liver esterase (PLE) gave a mixture of 3-endo-hydroxy-1,8-cineole (-)-3 and 3-endo-acetyloxy-1,8-cineole (+)-4. After chromatographic separation, (-)-3 was oxidized to (+)-2, while (+)-4 was hydrolysed to (+)-3 and then oxidized to (-)-2. The absolute configuration of either ketone 2 was established by VCD spectroscopy in combination with density functional theory (DFT) calculations at the B3LYP/DGDZVP level of theory, from where it followed that the (+)-2 enantiomer corresponds to (1R,4R)-1,3,3-trimethyl-5-oxo-2-oxabicyclo[2.2.2] octane and the (-)-2 enantiomer to the (1S,4S) molecule which is also in agreement with the absolute configuration deduced by the Mosher method for the starting chiral alcohols. Some literature inconsistencies are clarified. In addition, the enantiomerically pure monoester (1S,3S,4R,5R)-(-)-3-acetyloxy-5- hydroxy-1,8-cineole 6 and the ketoester (1R,3S,4R)-(+)-3-acetyloxy-5-oxo-1,8- cineole 7 were prepared from meso-diacetate 5 by enantioselective asymmetrization also using PLE.
KW - (+)-3-acetyloxy-5-oxo-1,8- cineole
KW - (+)-3-oxo-1,8-cineole
KW - (-)-3-oxo-1,8-cineole
KW - Absolute configuration
KW - Enantioselective asymmetrization
KW - Enantioselective hydrolysis
KW - Porcine liver esterase (PLE)
KW - Vibrational circular dichroism
UR - http://www.scopus.com/inward/record.url?scp=75549083331&partnerID=8YFLogxK
U2 - 10.1177/1934578x0900401116
DO - 10.1177/1934578x0900401116
M3 - Artículo
SN - 1934-578X
VL - 4
SP - 1537
EP - 1545
JO - Natural Product Communications
JF - Natural Product Communications
IS - 11
ER -