title: Synthesis of novel vitamin D3 analog with an additional ring annulated to A and seco-B rings.
abstract: A simple method for the synthesis of yet unknown 5E-vitamin D3 analogs with an additional six-membered ring connecting C-6 and C-19 was developed. Ring-closing metathesis (RCM) was used for efficient formation thereof from the corresponding 5E-isomers of 6-alkenyl vitamin D3 compounds which in turn were prepared from the 6-oxo-3,5-cyclovitamin D3. Reinvestigation of the Grignard reactions of this latter compound as well as the following acid-catalyzed cycloreversions showed discrepancies with the literature data describing the course of such processes.
authors.affiliation: Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Sokolowska
authors.affiliation: Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland. Electronic address: rasici@chem.uw.edu.pl.
authors.forename: Rafal R
authors.initials: RR
authors.lastname: Sicinski
mesh_terms: D060326:Chemistry Techniques, Synthetic; D002762:Cholecalciferol / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry; D003500:Cyclization; D008958:Models, Molecular; D008968:Molecular Conformation; D013237:Stereoisomerism
chemical_list: D002762:Cholecalciferol
keywords: 3,5-Cyclovitamin D(3); 5E-vitamin D(3); B-seco-steroids; Ring-closing metathesis; Vitamin D analogs