Stereodivergent de novo synthesis of branched amino sugars by lewis Acid promoted rearrangement of 1,2-oxazines.
Well concealed: 1,2-oxazines such as 1 rearrange under Lewis acidic conditions to bicyclic products of type 2, which can be incorporated into oligosaccharides as protected amino sugar equivalents. Subsequent reductive steps provide unusual oligosaccharides 3 having C2-branched 4-amino sugar units. Most of the reactions proceed with excellent stereocontrol and allow the synthesis of a collection of stereoisomers.
Pfrengle
Fabian
F
Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin, Germany.
Lentz
Dieter
D
Reissig
Hans-Ulrich
HU