R'15 16 d= NHCOCF3. R'= H 17 d= H, Rz-= NHCOCF3 an almost quantitative yield of known3 N-trifluoroacetyl-6. At higher temperature, with tetrahydrofuran as solvent, a small proportion of the L-Zyxo isomer was also formed. In contrast, the reduction of 13 gave the L- rib0 (7) and the L-xylo (8) isomers in the ratio-1: l.