1,3-PARALLEL C O INTERACTIONS IN ACYCLIC CARBOHYDRATES - THE CRYSTAL AND MOLECULAR-STRUCTURE OF 1-DEOXY-1-NITRO-D-ALTRITOL/

The crystal structure of 1-deoxy-1-nitro-D-altritol (1; C7H13NO7; spac e group P2(1),) was resolved to a final conventional residual factor o f R 0.081. The molecules showed a sickle conformation in which a 1,3-p arallel interaction (C//O) between C-6 and O-3 is tolerated, thus avoi ding a 1,3-parallel interaction (O//O) between O-3 and O-5 in a planar zigzag conformation. Interestingly, the bent conformation, which avoi ds all such interactions, was not adopted. The observed conformation r esembles that of D-altritol and D-altritol hexaacetate. A systematic s earch for the occurrence of such C//O interactions in the solid state conformations of acyclic carbohydrate derivatives revealed that this i s the conformation which usually is observed in those cases where comp ounds or part of compounds are of ribo configuration, but with a few r emarkable exceptions such as ribitol itself.