Diastereoselective syntheses of α-amino-β-hydroxyesters precursors of the ribosyl-diazepanone core of the liposidomycins

The diastereoselective syntheses of the O-protected ribosyl-β-hydroxy-α-amino esters 3 and 4, precursors of α-ribosyl-diazepanone core analogues of the liposidomycins, respectively, from the β-ketoesters 5 and 6 are described. The anti relationship between the two adjacent aminated and hydroxylated carbons was controlled by sequential hydrogenation of the β-ketoesters in the presence of chiral ruthenium catalysts and electrophilic amination of the resulting β-hydroxyesters.