Preparation of 2-deoxyaldoses from aldose phenylhydrazones

Acetylation of d-mannose phenylhydrazone gives acetylated d-arabino-1-phenyl-azo-1-(E)-hexene. Subsequent reduction with sodium borohydride produces 2-deoxy-d-arabino-hexose phenylhydrazone which, on hydrolysis, gives 2-deoxy-d-arabino-hexose. By a similar procedure 2-deoxy-d-lyxo-hexose, 2,6-dideoxy-l-arabino-hexose, and 2-deoxy-d-erythropentose can be prepared from d-galactose, l-rhamnose, and d-arabinose, respectively.