(+/-)-threo-2,3-dihydroxy-hexanoic acid

1-<2-Nitro-phenyl>-2,3-dioxo-heptan

(Z)-2-(((benzyloxy)carbonyl)amino)hex-2-enoic acid

1-Methoxy-1-triphenylphosphoranyliden-hexan-2-on

2-Methoxy-3-oxo-1-<2-nitro-phenyl>-hepten-(1)