ABSTRACT
The one-carbon ring expansion of 1-deoxy-1-thio-1,6-anhydrosugars, mediated by metal carbenes and proceeding through the intermediacy of sulfur ylides, has been proposed as a route for the synthesis of the tagetitoxin skeleton. Intermolecular reactions of such thioanhydrosugars with diazoesters afford a range of undesired products derived from the initially formed ylide, whereas use of an intramolecular process generates stable ylides which can be converted to the tagetitoxin skeleton by photo-Stevens rearrangement. Computational studies using density functional theory indicate that the photochemical rearrangement likely proceeds through a homolysis-recombination pathway.
Subject(s)
Azo Compounds/chemistry , Dicarboxylic Acids/chemical synthesis , Esters/chemistry , Oligosaccharides/chemistry , Organophosphorus Compounds/chemical synthesis , Sulfhydryl Compounds/chemistry , Dicarboxylic Acids/chemistry , Molecular Structure , Organophosphorus Compounds/chemistry , Photochemical Processes , Quantum TheoryABSTRACT
A synthesis of the 9-oxa-3-thiabicyclo[3.3.1]nonane ring system, which constitutes the core of the RNA polymerase inhibitor tagetitoxin, has been achieved through cyclisation of a thiol onto an electrophilic ketone.