The structures of the crystalline neutral complex of the isonicotinate ion with lanthanum(III) and of the crystalline salt of the cationic complex of nicotinic acid with holmium(III) have been determined by three-dimensional X-ray diffraction techniques. The complexes crystallize in P2l/c. The crystal parameters for Ho(C5H4NCOOH)3(H20)2Cr(NCS)6-2H20 are a = 9.578 (5) A, b = 25.954 (13) Á, c = 15.784 (7) Á, ß = 108.48 (2)°, deM = 1.797, dmtmi = 1.78 (2) g/cm3. The conventional discrepancy factor for this structure is 0.048 for 2989 diffractometer data. The crystal parameters for La-(C5H4NC00)3(H20)2 are a = 9.744 (3) Á, b = 19.908 (9) Á, c = 11.607 (4) A, ß = 68.20 (2)°, ¿caicd = 1.72, dmeasd = 1.70 (2) g/cm3. The discrepancy factor for this structure is 0.038 for 2554 diffractometer data. The primary structural units in both compounds are polymer chains made up of lanthanide(III) ions alternately linked by four and two bridging carboxylate groups. The eight coordination about each metal is completed by two water molecules. In the add complex, two additional waters and one hexaisothiocyanatochromate ion are also present. The acid ligand appears to be present as a zwitterion with the hydrogen attached to the nitrogen. These linear polymeric structures are compared with the dimeric structures found in the complexes of the rare earth metals with the nicotinate ion.Contribution prom the Department op Chemistry,

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The crystal structure of 7V-(l-a-naphthylethyl)-iV-(benzenesulfonyl)trichloromethanesulfenamide has been determined by three-dimensional X-ray diffraction. The molecule crystallizes in space group P2j with lattice constants a = 12.233 (6) Á, b = 8.546 (5) Á, c = 10.440 (5) Á, ß = 110.20 (1) °,Z = 2. Refinement of 1536 diffractometer data yielded a conventional discrepancy factor of 0.075. The structure found, which features a nearly planar trivalent nitrogen atom, has implications concerning torsional isomerism about heteroatom-heteroatom bonds (in this case between trivalent nitrogen and divalent sulfur) and concerning the possible existence of p-d ttbonding in S-N bonds. The incorporation of an asymmetric carbon atom of known configuration allowed the assignment of absolute configuration to the sulfenamide chiral axis.he structure and conformational analysis of molecules with sulfur-nitrogen bonds has been a topic of recent interest. A number of X-ray crystallographic structure determinations of molecules with different kinds of sulfur nitrogen bonds have appeared.2-4 In (1) This work was supported in part by grants from the National Science Foundation (No. GP-17092 and GP-15070) and the Edmond de Rothschild Foundation. We thank the Wayne State University Computing and Data Processing Center for the use of their facilities.(2) (a

The previously reported high rates of acetylcholinesterase‐catalysed hydrolysis of (±)‐cis‐ and (±)‐trans‐2‐dimethylaminocyclohexyl acetate methiodide (Baldridge, McCarville & Friess, 1955) have been re‐investigated, the enantiomers of each geometrical isomer being used. The cis‐enantiomers were inactive as substrates and the trans‐enantiomers were hydrolysed at a very slow rate. These results are confirmed by studies on muscarinic tissue (guinea‐pig ileum) in which only a weak stimulatory response was given with the trans‐enantiomers (the cis‐enantiomers were inactive). With each of the test systems used, the acetylcholine receptor showed an inversion of the “normal” configurational specificity although the enantiomer potency ratio was small, a phenomenon which has been observed in previous reports of inversion of configurational specificity.

The preparation of the enantiomers of cis-and trans-2-dimethylaminocyclohexylacetate methiodide (potential substrates for the enzyme acetylcholinesterase) is reported. The absolute configuration of the cis-enantiomers has been shown from their relationship with compounds of known configuration. The configuration of the transenantiomers is inferred from 0.r.d. spectral studies.IN a study of synthetic substrates of the enzyme acetylcholinesterase, it has been reported that both (-t-)-cisand( &) -trans-2-dimet h ylaminocyclohexyl acetate methiodide are subject to enzyme-catalysed hydrolysis ; the (&)-cis-isomer is hydrolysed at a slightly greater rate than the (&)-trans-isomer at their respective optimum substrate concentrations. This difference in activity has been suggested to be due to a difference in the separation of the functional groups necessary for binding to form an enzyme-substrate complex. (Fries1 reports N+ to acyl-0 separation as 2-9-36 A for tram-and 2.5-2.9 A for cis-isomer.) However, studies of the conformation of 1,2-disubstituted cyclohexane derivatives suggest that the separation of the above functional groups in these compounds should be essentially identical (2.9 from Drieding models) and an alternative explanation for the differences in behaviour of the two compounds with the enzyme must be sought.Enzyme catalysed reactions are nearly always stereospecific, and this phenomenon has been adequately