Pentafluorophenyl (3R,4R,5S)-5-{[(3R,4R,5S)-5-azidomethyl-3,4-dimethoxy-2,3,4,5-tetrahydrofuran-3-carboxamido]methyl}-3,4-dimethoxy-2,3,4,5-tetrahydrofuran-3-carboxylate

Abstract

The title compound, C22H25F5N4O9, is a stable pentafluorophenyl ester intermediate in the synthesis of novel homo-oligomeric structures containing branched carbon chains. The structure is epimeric to the previously characterized dimeric pentafluorophenyl ester with stereochemistry (3R,4R,5R), which was synthesized using d-ribose as starting material. The crystal structure of the title molecule removes any ambiguities arising from the relative stereochemistries of the six chiral centres. Two hydrogen bonds, bifurcating from the NH group, stabilize the crystal: one intramolecular and one intermolecular, both involving O atoms of the methoxy groups. The asymmetric unit contains two independent molecules not related by any pseudo-symmetry operators. The major conformational differences are localized, leading to one molecule being extended compared to the other. The collected crystal was twinned (twin ratio is 0.939:0.061), and the azide group is positionally disordered over two positions in one molecule [occupancy ratio 0.511 (18):0.489 (18)].