Regioselective asymmetric aminohydroxylation of precursors to 2,3,6-trideoxy-3-aminohexoses

The catalytic asymmetric aminohydroxylation (AA) of 5-substituted-pent-2-enoates 8 and 17 was investigated as a route to 2,3,6-trideoxy-3-aminohexoses. The AA of ester 8, which bears a dimethyl acetal at C-5, favoured formation of the α-amino regioisomer 11 with optimum regioselectivity being observed using (DHQ)2AQN as the chiral ligand and the chloramine salt of ethyl carbamate as the nitrogen source. Ester 17, which has a 4-methoxyphenoxy group at C-5, undergoes highly regioselective AA affording the β-amino regioisomer 19 in excellent enantiomeric excess, thereby establishing that introduction of this aromatic group leads to a superior substrate for AA.