title: The case for configurational stability of H-phosphonate diesters in the presence of diazabicyclo[5.4.0]undec-7-ene (DBU).
abstract: Configurational stability of dinucleoside H-phosphonates and the stereochemical course of their sulfurisation in the presence of diazabicyclo[5.4.0]undec-7-ene (DBU) were investigated using 31P NMR spectroscopy. It was found that under the reaction conditions and irrespective of the type of protecting groups present in the nucleoside moieties, the H-phosphonate diesters investigated did not undergo any detectable epimerisation at the phosphorus centre, and their sulfurisation with elemental sulfur in the presence of DBU, proceeded stereospecifically. Thus, we could not confirm reports from another laboratory on a stereoselective course of sulfurisation of H-phosphonate diesters and the corresponding acylphosphonates in the presence of DBU.
authors.affiliation: Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Johansson
authors.forename: J
authors.initials: J
authors.lastname: Stawinski
mesh_terms: D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology*; D004355:Drug Stability; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D063065:Organophosphonates / Q000737:chemistry*; D010759:Phosphorus Isotopes; D013237:Stereoisomerism; D013455:Sulfur / Q000737:chemistry
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D063065:Organophosphonates; D010759:Phosphorus Isotopes; D013455:Sulfur; C031033:1,8-diazabicyclo(5.4.0)undec-7-ene