title: Epimerization of C-22 in (25R)- and (25S)-sapogenins.
abstract: Most of the naturally occurring steroidal sapogenins (C-23 non-substituted frameworks), possess an R configuration at the spiro C-22 center. Their C-22 epimers have become important targets in biological research. This paper describes a procedure to obtain 22S-spirostans from 22R-sapogenins and pseudosapogenin skeletons, without affecting the chirality at either C-25 or C-20. An optimal way to synthesize the pair of C-22 stereoisomers of 23-acetyldiosgenin is also reported. The latter was obtained from a 22,26-epoxycholestane or from 23-acetylfurostene compounds.
authors.affiliation: Instituto de Química Aplicada, Universidad del Papaloapan, Circuito Central # 200, Colonia Parque Industrial, Tuxtepec, Oax. 68301, Mexico.
authors.forename: Omar
authors.initials: O
authors.lastname: Viñas-Bravo
authors.affiliation: Facultad de Ciencias Químicas, Benemérita Universidad Autónoma de Puebla, Ciudad Universitaria, Puebla, Pue. 72570, Mexico.
authors.forename: Penélope
authors.initials: P
authors.lastname: Merino-Montiel
authors.affiliation: Facultad de Ciencias Químicas, Benemérita Universidad Autónoma de Puebla, Ciudad Universitaria, Puebla, Pue. 72570, Mexico.
authors.forename: Anabel
authors.initials: A
authors.lastname: Romero-López
authors.affiliation: Facultad de Ciencias Químicas, Benemérita Universidad Autónoma de Puebla, Ciudad Universitaria, Puebla, Pue. 72570, Mexico. Electronic address: maria.montiel@correo.buap.mx.
authors.forename: Sara
authors.initials: S
authors.lastname: Montiel-Smith
authors.affiliation: Facultad de Ciencias Químicas, Benemérita Universidad Autónoma de Puebla, Ciudad Universitaria, Puebla, Pue. 72570, Mexico.
authors.forename: Socorro
authors.initials: S
authors.lastname: Meza-Reyes
authors.affiliation: Facultad de Ciencias Químicas, Benemérita Universidad Autónoma de Puebla, Ciudad Universitaria, Puebla, Pue. 72570, Mexico.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Meléndez
authors.affiliation: Facultad de Ciencias Químicas, Benemérita Universidad Autónoma de Puebla, Ciudad Universitaria, Puebla, Pue. 72570, Mexico. Electronic address: jesus.sandoval@correo.buap.mx.
authors.forename: Jesús
authors.initials: J
authors.lastname: Sandoval-Ramírez
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D012502:Sapogenins / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D012502:Sapogenins
keywords: 22-epi-Sapogenins; 23-Acetyldiosgenin; Boron trifluoride etherate; Pseudosapogenins