Diastereo‐ and enantioselective synthesis of 1,2:5,6‐diepoxy‐4‐hydroxyalkyl carbamates. – regioselective ring opening and their transformation into doubly C‐branched deoxy sugar analogues

Abstract

AbstractEnantiomerically enriched (Z)‐anti‐3,5‐dialkyl‐4‐hydroxy‐1,5‐alkadienyl N,N‐diisopropylcarbamates 12, readily obtained by the homoaldol approach, were oxidized with essentially complete diastereoselectivity to afford 1,2:5,6‐diepoxides 14 of D‐allo configuration. Conditions were worked out for the transformation of 14 into furanosides of types 19, 21, and 22 and for the selective nucleophilic introduction of carbon residues into the 6‐position to give chain‐elongated analogues 25. Altogether, a “brick‐box system” for the enantioselective construction of polystereogenic building blocks with a few synthetic steps from simple achiral starting materials [(E)‐2‐alkenyl carbamates of type 9 and 2‐alkyl‐2‐alkenals (11)] and nucleophiles, like Grignard reagents, is demonstrated.