Regio- and stereoselective cleavage of steroidal 22-oxo-23-spiroketals catalyzed by BF3·Et2O.
The regioselective opening of the F ring of 22-oxo-23-spiroketals using BF3·OEt2 in acetic anhydride yielded novel cholestanic frameworks with pyranone E ring 20-23. The structures of the new derivatives of botogenin, diosgenin, hecogenin and tigogenin thus obtained were established using one and two dimensional (1)H, (13)C experiments (DEPT, COSY, HETCOR, HMBC). The X-ray diffraction analysis unequivocally confirmed the R configuration at C-23 in the starting 22-oxo-23-spiroketal 18 and the Z configuration of the C23-C24 double bond in the reaction product 20.
Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ed. B-1, C.U., Morelia, Michoacán 58030, Mexico.
Alejandro Corona
AC
Díaz
Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ed. B-1, C.U., Morelia, Michoacán 58030, Mexico.
J
J
Pablo García Merinos
Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ed. B-1, C.U., Morelia, Michoacán 58030, Mexico. Electronic address: ylopez@umich.mx.
Yliana
Y
López
Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ed. B-1, C.U., Morelia, Michoacán 58030, Mexico.
J
J
Betzabe González Campos
Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ed. B-1, C.U., Morelia, Michoacán 58030, Mexico.
Rosa E
RE
del Río
Departamento de Química, CINVESTAV-IPN, Apdo. Postal 14-740, México, D.F. 07000, Mexico.
Rosa
R
Santillan
Facultad de Química, Departamento de Química Orgánica, Universidad Nacional Autónoma de México, México, D.F. 04510, Mexico.
Norberto
N
Farfán
Institute of Chemistry, University of Białystok, Piłsudskiego 11/4, 15-443 Białystok, Poland.
Jacek W
JW
Morzycki
D001880:Boranes / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D004986:Ether / Q000737:chemistry*; D005663:Furans / Q000737:chemistry*; D008968:Molecular Conformation; D013141:Spiro Compounds / Q000737:chemistry*; D013237:Stereoisomerism
D001880:Boranes; D005663:Furans; D013141:Spiro Compounds; C520774:spiroketal; D004986:Ether; C021274:boron trifluoride
Botogenin; Cholestanes; Diosgenin; Hecogenin; Spirostanes; Tigogenin