Zur Kenntniss des Claus'schen Dichinolins

Electron diffraction study of the structures of NbS2 and order—disorder in Cu-intercalated NbS2

“…An interesting property possessed by NbS,, in common with many similar layer structures, is the ability to accommodate additional metal atoms between the adjacent S-S layers of the crystal. Thus in non-stoichiometric Nbl+,S, extra Nb atoms are situated in some of the octahedral holes between adjacent S layers [3]. The transition metals Ti, V, Cr, Mn, Fe, Co, and Ni can also be l) On leave from the "J.…”

The possible role of conformational isomerism in the biological actions of acetylcholine

“…The validity of this interpretation was later criticized (Dunitz, 1963) and a reinvestigation of the crystal structure of acetylcholine bromide (Canepa, Pauling & Sorum, 1966) has shown the sole presence of a quasi-ring form (4) in which the interatomic angles are such that the methyl group (C-1) seems to form a bent hydrogen bond through one of its hydrogen atoms to the acyloxy oxygen atom (0-1). The structure of acetylcholine in the crystal lattice is thus very similar to those of choline chloride (5) (Senko & Templeton, 1960) and L(+)-muscarine iodide (6) (Jellinek, 1957). In the latter the stability of the quasi-ring conformation has been attributed to C-H ----0 bonding (Sutor, 1963).…”

“…The appearance of nicotinic as well as muscarinic activity in the muscarones (e.g. 34) can perhaps also be attributed to anincreasedfavourability of the extended conformation as compared to the situation in muscarine and it will be interesting to learn whether an X-ray study of crystalline muscarone iodide will demonstrate the existence of such a conformation (342) rather than a quasi-ring conformation (6) as is characteristic of muscarine iodide (Jellinek, 1957). If indeed stabilization of the quasi-ring conformation of muscarine is due to intramolecular NC-H ----0 hydrogen bonding (Sutor, 1962(Sutor, , 1963 then the polarization of the 0x0 group in muscarone could perhaps destabilize the quasi-ring form through relayed inductive effects (35) but complexities are introduced by the possibility that muscarone could interact with the receptor in its enol form (Waser, 1961a).…”

“…It is of course possible that some, if not all, of these discrepancies arise from the compound concerned inducing acetylcholine release and not exerting a direct action in its own right. However, the fact that L(+)-muscarine (14) in the solid state exists in a quasi-ring conformation (Jellinek, 1957) which corresponds closely with the quasi-ring conformer (4) of acetylcholine (Canepa & others, 1966) might suggest that this conformation (4) rather than the fullystaggered conformation (2) of acetylcholine is more likely to be involved at the muscarinic sites. In addition, should the molecules of both acetylcholine and nicotine have a two point attachment at the nicotinic receptor,…”

The Application of Polychalcogenide Salts to the Exploratory Synthesis of Solid State Multinary Chalcogenides at Intermediate Temperatures

“…Of note in this chemistry is the unusual tetrahedral geometry about the Nb and Ta atoms. A trigonal prismatic geometry is common for both metals in MS2 (39) and most of their other binary chalcogenides (40), although the discrete tetrahedral anion, (MQ4),-, is known for the sulfides and selenides of both metals (41).…”