Synthesis of and NMR studies on the four diastereomeric 1-deoxy-D-ketohexoses von Jones, N, Jenkinson, S, Soengas, R, Fanefjord, M, Wormald, M, Dwek, R, Kiran, G, Devendar, R, Takata, G, Morimoto, K, Izumori, K, Fleet, G