title: Inorganic Cyanide as Protecting Group in the Stereospecific Reconstitution of Vitamin B12from an Artificial Green Secocorrinoid.
abstract: The synthesis of vitamin B12in four steps from an artificial green secocorrinoid is presented. The stereospecific reconstitution of the B-ring of the cobalamin involves a quantitative and rapid ligand-centered radical ring closure reaction leading first to a new B12derivative with antivitamin activity that is subsequently converted to the natural product. Chemoselectivity in the one-electron reduction of the macrocycle was achieved by introducing inorganic cyanide as an axially coordinating protecting group of the otherwise reduction-sensitive CoIII-ion. The integrity of structure and function of the reconstituted natural product was unequivocally proven by single crystal structural analysis and a microbiological assay using Lactobacillus leichmannii.
authors.affiliation: Department of Chemistry, University of Zurich , Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
authors.forename: Lucas
authors.initials: L
authors.lastname: Prieto
authors.affiliation: Department of Chemistry, University of Basel , Spitalstr. 51, CH 4056 Basel, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Neuburger
authors.affiliation: Department of Chemistry, University of Zurich , Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Spingler
authors.affiliation: Department of Chemistry, University of Zurich , Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
authors.forename: Felix
authors.initials: F
authors.lastname: Zelder