Carbon—hydrogen spin—spin coupling constants

Rhodium (II) catalyzed reactions of diazo-carbonyl compounds

The Nature and Analysis of Substitutent Electronic Effects

Publisher Summary The chapter focuses on the methods for determination of conformation of sugars and their derivatives The study of the conformations of organic molecules pointed out that six membered ring-systems can exist free from bond-angle strain, in two puckered forms, the flexible or asymmetric form, and the rigid or symmetric (chair) form Boat or skew conformations are considered possible if the nonbonded interactions between the substituents in the chair conformation are too large The conformational analysis of saturated five and six-membered heterocycles, presenting data relevant to the carbohydrate field, is also presented The various techniques discussed in the chapter are X-ray crystallography andspectroscopic methods—namely infrared spectroscopy, microwave spectroscopy, and nuclear magnetic resonance spectroscopy Methods based on optical activity and those that involve formation of complexes in cuprammonia, and dipole moments are also discussed Several theoretical studies on the conformations of the aldopyranoses are also reported By calculating the extent of atomic (Van der Waals) overlap of non-bonded atoms, the relative stabilities of the chair conformations of the aldopyranoses are estimated The chapter also describes methods for conformations of acyclic sugars and their derivatives, pyranoid sugar derivatives, and furanoid sugar derivatives, in their crystalline state and in solution The chapter also discusses anomeric effect and empirical approaches to predict favorable conformation

Conformational Analysis of Sugars and Their Derivatives

Recent advances in the Stevens rearrangement of ammonium ylides. Application to the synthesis of alkaloid natural products

The favored conformations of the pyranose rings of several acetonated α-L-sorbo- and β-D-fructopyranoses have been revealed by proton magnetic resonance spectroscopy. The conformations of the rings of the pyranoses are unchanged by the introduction of 1,2-O- or 1,3-O-isopropylidene groups in α-orientation of L-sorbose, but they are affected by the introduction of the 2,3-O-isopropylidene group. These findings support the fact that 2,3-O-isopropylidene-α-L-sorbopyranose was not obtained by the acetonation of L-sorbose. The rings of diacetonated D-fructopyranoses with a cis-fused acetal ring adopt a distorted conformation; however, those of diacetonated L-sorbopyranoses with a trans-fused acetal ring are only slightly distorted from the stable 1C conformation. Angyal’s anticipation of the difficult acetalation of the trans-glycol of a pyranose has been further experimentally supported.

Conformational Studies of Acetonated α-L-Sorbo- and β-D-Fructopyranoses by Means of Proton Magnetic Resonance Spectroscopy

Novel substituent effects in 1H and 13C NMR spectra of 4-and 4'-substituted N-benzylideneanilines

A series of L-sorbofuranose derivatives have been studied by PMR spectroscopy in order to determine their favored conformations from the coupling constants obtained by applying the spin-decoupling techniques and the solvent effects of benzene at 100 MHz. The coupling constants J3,4, have disclosed that the furanose ring of methyl 1,3,4,6-tetra-O-acetyl-α-L-sorbofuranoside (IIa) in solutions has a conformation close to a C3-endo-C4-exo half-chair, while that of its β-anomer (IVa) has a C3-exo-C4-endo half-chair conformation. Their conformations are unchanged over the temperature range of 32–74°C, but they are affected by the introduction of a 4,6-O-or 2,3-O-isopropylidene group, either of which locks the furanose ring to a C3-exo-C4-endo half-chair conformation. This effect is thought to play an important role in the exclusive formation of 2,3:4,6-di-O-isopropylidene-α-L-sorbofuranose (XII) during the acetonation of L-sorbose.

Acetonated Sorbofuranoses and Their Favored Conformations as Determined by Proton Magnetic Resonance Spectroscopy

Data on 13C chemical shifts and 13C1H spin coupling constants of norbornane (1), norbornene (2), norbornadiene (3), benzonorbornene (4) and benzonorbornadiene (6) are reported. The non-equivalence in J(13CH) values determined from the two bridge methylene proton signals in 2,2,3,3-tetradeuteriobenzonorbornene (5) and 6 is briefly discussed. The extraordinary deshielding of the bridge methylene carbon in 6 has been noted.

NMR studies of bridged ring systems: XIX—13C1H spin coupling and 13C chemical shift of the bridge methylene in benzonorbornene and benzonorbornadiene†

NMR studies of bridged ring systems. XVIII. Remarkable steric γ effect upon 13C chemical shifts in tricyclo[3.2.1.O2,4]octenes and its application to 13C signal assignment of 9-isopropylidenebenzonorbornene derivatives

Shiroh Satoh

Papers

Conformational Studies of Acetonated α-L-Sorbo- and β-D-Fructopyranoses by Means of Proton Magnetic Resonance Spectroscopy

Novel substituent effects in 1H and 13C NMR spectra of 4-and 4'-substituted N-benzylideneanilines

Acetonated Sorbofuranoses and Their Favored Conformations as Determined by Proton Magnetic Resonance Spectroscopy

NMR studies of bridged ring systems: XIX—13C1H spin coupling and 13C chemical shift of the bridge methylene in benzonorbornene and benzonorbornadiene†

NMR studies of bridged ring systems. XVIII. Remarkable steric γ effect upon 13C chemical shifts in tricyclo[3.2.1.O2,4]octenes and its application to 13C signal assignment of 9-isopropylidenebenzonorbornene derivatives