. Assignments for the 13C chemical shifts of methyl aldopento-and hexofuranosides and of cyclopentane polyols are reported, and these chemical shifts are evaluated with respect to all combinations of configurational arrangements of the ring substituents. A cis configuration of vicinal substituents is generally associated with a substantial increase in shielding, a s compared with the trans analog. Among the furanosides, however, changes in configuration involving 0-3 and C-5 are accompanied by a complex shielding pattern: e.g., effects on C-3 are minor, C-4 is more shielded in cis than in trans isomers, and C-4 and C-5 of hexosides are more shielded than those of pentosides. Variations in shielding attributable to cis or trans arrangements of substituents in a 1,3-relationship are encountered in only a few instances; however, it is noteworthy that C-4 is less shielded when 0-1 and 0-3 are cis than when trans. These diverse effects are considered also in relation to steric interactions and to conformational influences on 13C chemical shifts in the five-membered ring series. R. GEORGE S. RITCHIE, NATSUKO CYR, BRIAN KORSCH, HANS J. KOCH et ARTHUR S, PERLIN.Can. J. Chem. 53,1424Chem. 53, (1975.On rapporte les attributions de d6placements chimiques du I3C pour les aldopento-et hexofurannosides de m6thyle et pour une sCrie de cyclopentanepolyols; on &value ces d6place-ments chimiques par rapport a toutes les combinaisons d9&angements configurationnels des substituants du novau. Par o~~o s i t i o n aux analogues trans. on associe dn6ralement une augmentation substantielle du biindage avec une configuration cis des substituants vicinaux. Toutefois parmi les furannosides, les changements de configuration impliquant 0 -3 et C-5 sont accompagnes par un patron de blindage complexe, e.g. les effets sur C-3 sont mineurs, C-4 est plus blind6 dans les isomkres cis que dans les isomeres trans et C-4 et C-5 des hexosides sont plus blind& que ceux des pentosides. On ne rencontre que quelques cas oh des variations dans le blindage sont attribuables aux arrangements cis et trans des substituants en position 1,3; toutefois il est a noter que C-4 est moins blind6 quand 0-1 et 0-3 sont cis que lorsqu'ils sont trans. On considere aussi ces divers effets en relation avec les interactions stkriques et les influences conformationnelles sur les d6placements chimiques du 13C dans une skrie de cycles a cinq membres. [Traduit par le journal] IntroductionEarlier studies (1-6) have dealt with configurational and conformational effects on 13C n.m.r. chemical shifts in the pyranose series of carbohydrates and selected substituted cyclohexanols. The recognition of such steric effects in the spectra of these compounds proved to be relatively straightforward because of the unique geometry of the six-membered ring: namely, the existence of two chair conformations, in which the substituents are either axial or equatorial. By contrast, the furanose and cyclopentane rings are more

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A study of the pyrolysis of Athabasca bitumen has been made using the pyrolysis-gas chromatographic technique. At temperatures below 500 °C the evolution of volatile products from bitumen is dominated by a distillation process. Pyrolysis becomes more important in the higher temperature regions; by 950 °C deep-seated degradation to gases and light ends is dominant. The apparent activation energy of the low-temperature process is reported.

The addition of the pseudohalogen iodine nitrate (IONO2) to the endocyclic alkenic bond in benzyl 2-O-benzyl-3,4-dideoxy-α-D-glycero-pent-3-enopyranoside (3) is described. The stereochemistry and regiochemistry of addition were elucidated by chemical degradation, 1Hmr spectroscopy, mass-spectral analysis, and polarimetry. A synthetic route to 4′-thiocordycepin (20) from compound 3, by way of the intermediacy of the preponderant iodine nitrate adduct of 3, namely, benzyl 2-O-benzyl-3-deoxy-3-iodo-4-O-nitro-β-L-lyxopyranoside (4), is also described.