1 nor in the 1 ' form, but they are present in a quasiaromatic structure between the resonance limit forms 1 and l', as represented by the following structure: 6 H This structure is supported by X-ray The electron density projection shows that the six-membered chelate ring is approximately planar and also essentially coplanar with the two benzene rings. Furthermore, their bond angles lie in the neighborhood of 120". This is what should be expected in a n aromatic system. The quasiaromatic nature of the chelate structure was also substantiated by polarographic analysis. The stabilization energy of the chelated sugar phenyl-osazones was found to be about 10 kcal.,'mole higher, than for the nonchelated sugar methylphenylosazones. This value is much higher than the usual chelation energy. Besides, the proposed structure may explain the sharp difference between the C-1 and C-2 phenylhydrazone groups in almost all their reactions, such as methyl-ation, l 5 osotriazole formation,I6 etc., as well as the privileged position 17-l 9 of the C-3 hydroxyl in the sugar osazones. of the quasiaromatic chelate system. Experimental The n.m.r. spectra of the compounds reported in this communication were determined at 60 Mc. with tetramethylsilane as an internal reference on an A-60 Varian Associates spectrometer, Palo Alto, Calif. High-resolution n.m.r. spectrum at HR 100 Mc. of tetra-0-acetyl-D-galactose phenylosazone and de-coupling with the double resonance method was determined by Dr. All the compounds used had melting points reported in the literature. 20-27 Deuteration. Deuteration of the nonchelated imino group was effected by shaking the deuteriochloro-form solution of the acetylated osazones with deuterium oxide at room temperature for a few minutes. The deuteration of the imino group involved in the chelation was achieved by shaking the deuteriochloroform solution with deuterium oxide in a fused glass tube and by heating in a water bath for 10 to 30 min. Acknowledgment. We would like to express our appreciation to Professor M.-M. Janot (Paris) for his suggestion, and to Mrs. M. Mester and Mrs. L. Allais for their assistance. This is due to the electron-attractive effect N.m.r. Spectra. Conformations of the furanose ring in nucleic acids and other carbohydrate derivatives arrived at f r o m X-ray and neutron diffraction data are presented. The puckering in the furanose ring, involving the C-2' or C-3' atom, results in four conformeric possibilities: C-2'-endo, C-3'-exo, C-3'-endo, and C-2'-exo; their differences and similarities are discussed. The puckering when described as a …