Selective Functionalization of the 1,6-Anhydro Moiety and of the Double Bond of Levoglucosenone

Abstract

Through a very efficient, step-economical (only 4 steps) and diastereoselective-chemoselective procedure, bio-based levoglucosenone has been converted into a versatile azide, which may be regarded as a synthetic equivalent of a 6-amino-6-deoxysugar. This procedure involves: a) reduction of the ketone of LGO; b) opening of the 1,6-anhydro moiety with acetic anhydride and a protic acid to give a triacetate; c) biocatalytic deacetylation of the primary alcohol; d) substitution of the alcohol with the azide. The overall yield from LGO is 59%. This azide has been employed in two diversity-generating protocols: Huisgen-Sharpless 1,3-dipolar cycloaddition with alkynes (also derived from bio-based phenols), and the Ugi multicomponent reaction. Furthermore, the double bond has been dihydroxylated with nearly complete diastereoselection both at the azide level or on the triazoles derived from Huisgen cycloadditions, furnishing compounds with the rare D-altro configuration. The chemistry described in this work may help in devising synthetic applications of levoglucosenone, a densely functionalised product of pyrolysis of lignocellulosic matter. †Electronic Supplementary Information (ESI) available: