Regioselective cleavage of 22-oxo-23-spiroketals. Novel cholestanic frameworks with pyranone and cyclopentenone E rings on the side chain

• Published in: Steroids Vol. 77; no. 5; pp. 534 - 541
• Main Authors: López, Yliana, Rodríguez, León, del Río, Rosa E., Farfán, Norberto, Morzycki, Jacek W., Santillan, Rosa
• Format: Journal Article
• Language: English
• Published: NEW YORK Elsevier Inc 01.04.2012; Elsevier
• Subjects: 22-Oxo-23-spiroketal; Acetic Anhydrides - chemistry; Biochemistry & Molecular Biology; Biological and medical sciences; Cholestane; Cholestanes - chemistry; Crystallography, X-Ray; Cyclopentanes - chemistry; Diosgenin - chemistry; Endocrinology & Metabolism; Fundamental and applied biological sciences. Psychology; Furans - chemistry; Hydrochloric Acid - chemistry; Life Sciences & Biomedicine; Magnetic Resonance Spectroscopy - methods; Models, Chemical; Molecular Structure; NMR; Pyrones - chemistry; Sapogenin; Sapogenins - chemistry; Science & Technology; Spiro Compounds - chemistry; Spirostans - chemistry; Stereoisomerism; Vertebrates: endocrinology; Sapogenin; Cholestane; NMR; 22-Oxo-23-spiroketal; REARRANGEMENT; PRODUCTS; SAPONINS; C-22; STEROID SAPOGENINS; X-RAY; BF3-CENTER-DOT-ET2O; DERIVATIVES
• ISSN: 0039-128X; 1878-5867
• DOI: 10.1016/j.steroids.2012.01.018

► The regioselective opening of 22-oxo-23-spiroketals using HCl in Ac2O is reported. ► Novel cholestanic frameworks with pyranone or cyclopentenone E rings were obtained. ► The structures of the new derivatives were established using NMR analysis. ► The X-ray analysis for compound 11b confirmed the 23R configuration at C-23. ► A mechanism that accounts for the stereochemistry of the products is proposed. The regioselective opening of the F ring of 22-oxo-23-spiroketals using a saturated solution of HCl in acetic anhydride yielded novel cholestanic frameworks with pyranone or cyclopentenone E rings. The structures of the new derivatives of sarsasapogenin, diosgenin and hecogenin thus obtained were established using one and two dimensional 1H, 13C experiments (DEPT, COSY, HETCOR, HMBC, ROESY, and NOESY). The X-ray analysis for compound 11b confirmed the 23R configuration for the new stereogenic center.