Furanosylidene and iminofuranosylidene complexes: Synthesis by stoichiometric olefin metathesis and ring-opening/mitsunobu-recyclization sequence

Stoichiometric olefin metathesis of highly electrophilic Fischer diphenyl-c arbene complexes of chromium and tungsten 3 and 4 with D-mannose- and D-gul ose-derived furanoid exo-glycals has been applied to the synthesis of furan osylidene complexes 5-8. E-selective ring-opening aminolysis with a range o f primary amines and subsequent recyclization under Mitsunohu conditions pr ovides an easy access to iminofuranosylidene complexes of the talo and allo -series 20-26, The scope of this sequence is demonstrated by the synthesis of a novel class of organometallic glycoconjugates.