Highly stereoselective synthesis of 3-amino-3,6-dideoxy-aldohexoses by tintriflate mediated aldol condensation reaction of tricarbonyl iron alpha-aminodienone complexes. Total synthesis of multiprotected mycosamine.

The divalent tin enol ether of the racemic N-BOC alpha-aminodienone tricarb onyliron complex 4 reacts with both enantiomers of protected lactaldehydes to predominantly yield one optically active ketol diastereoisomer (45 %). F rom the enantiomerically pure complex (S)-(+)-4 and (R)-(+) tert butyldimet hylsilyloxylactaldehyde this ketol is obtained almost alone (isolated 86 %) . From there, the multi-protected 3-amino-3,6-dideoxy-D-aldohexose mycosami ne is obtained in a few high yielding steps (decomplexation, stereospecific reduction to a 1,3-diol, transformation into a diacetate and ozonolysis; a bsolute configurations S,S,SR). By reduction of the ketol before decomplexa tion, the stereochemistry of the reaction is completely reversed (control b y the Fe(CO)(3) and nor by the hydroxyl group), giving also access to the R ,S,SR series, (Structures determined by X-ray diffraction). (C) 1999 Elsevi er Science Ltd. All rights reserved.