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By stereospecific adduct formation between mercuric acetate and unsaturated fatty acids, derivatives are obtained suitable for NMR determination ofcis-trans ratio. The preparation and optimal experimental conditions are determined. Experimental data are found to be within a few per cent of the true values.

Most studies including double quantum transitions (DQT's) in the analysis of NMR spectra have been reported for three-spin systems. In the present paper it is shown by two examples that the method may be extended to some types of larger molecules, where it is possible to isolate a three-spin subsystem by spin decoupling. For the subsystem the DQT's have then been used to obtain the energy-level diagram yielding the local parameters of the subsystem. In the detection and assignment of the DQT's spin-tickling experiments involving the DQT's have been performed.

The preparation of 2-thienylcarbonyl and 2-thiazolylcarbonyl fluorides from the corresponding carboxylic acids is described. The n.m.r. spectroscopic parameters are determined and compared with experimental data for similar systems. Theoretical values for the coupling constants have been obtained in the CNDO/2 approximation and they are compared with the experimental data.

Carbon-13 spin-lattice relaxation times (T1) have been determined for the carbon in the octapeptide hormone [5-isoleucine]-angiotensin II in aqueous solution. Two possible models for molecular motion are considered: isotropic overall motion of the hormone with internal motion of some residues and anisotropic overall molecular motion. The data are interpreted in detail using the former model. The alpha carbons of the peptide backbone are all equally restricted in their motion. The correlation time for overall molecular reorientation, calculated from an everage T1 value of 95 msec for the alpha carbons in the peptide backbone, is ca. 5 times 10-10 sec. The carbons in the side chains are more mobile than those in the peptide backbone, with the exception of the side chain of the Tyr residue which does not undergo rapid segmental motion. We propose that [5-isoleucine]-angiotensin II has a restricted backbone conformation and that the alpha carbons of the N- and C-terminal residues are constrained to nearly the same extent as the remaining alpha carbons in the peptide backbone. Chemical shift data indicate that the Pro residue adopts the trans conformation about the His-Pro bond and that the imidazole ring of His has a strong preference for the N-tau -H tautomer.

The bicyclic 3-isoxazolol amino acids (RS)-3-hydroxy-4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridine-4-carboxylic acid (5, 4-HPCA) and (RS)-3-hydroxy-4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridine-6-carboxylic acid (11, 6-HPCA) were synthesized as model compounds for studies of the structural requirements of central excitatory amino acid neurotransmitter receptors. 4-HPCA was synthesized via introduction of a methoxycarbonyl group into the 4-position of the lithiated N-nitroso intermediate 1. The key reaction in the synthesis of 6-HPCA is an intramolecular N-alkylation of the appropriately substituted acetamidomalonate derivative 7 using sodium hydride as a base. On the basis of the pKA values for 4-HPCA the existence of an intramolecular hydrogen bond in the zwitterionic form of this amino acid is proposed. 6-HPCA was shown by 1H NMR spectroscopy to adopt preferentially a conformation with the carboxylate group in an equatorial position. 4- and 6-HPCA were tested as agonists and antagonists at excitatory amino acid receptors on neurones in the cat spinal cord using microelectrophoretic techniques. Neither compound showed significant effects at these receptors.

The syntheses of (3RS,4RS)-4-hydroxypiperidine-3-carboxylic acid (4), (3RS,5SR)-5-hydroxypiperidine-3-carboxylic acid (20), (3RS,4SR)-4-acetamidopiperidine-3-carboxylic acid (10), and (3RS,5SR)-5-acetamidopiperidine-3-carboxylic acid (18), related to the specific gamma-aminobutyric acid (GABA) uptake inhibitors (RS)-piperidine-3-carboxylic acid (nipecotic acid) and (3RS,4SR)-4-hydroxypiperidine-3-carboxylic acid (21), are described. Furthermore, (3RS,4SR)-3-hydroxypiperidine-4-carboxylic acid (14), related to the specific GABA agonist piperidine-4-carboxylic acid (isonipecotic acid), has been synthesized. The structures of 4, 10, 14, 18, and 20 have been established by 270-MHz 1H NMR spectroscopic analyses. The affinity of the compounds for the GABA receptors and for the neuronal (synaptosomal) GABA uptake system in vitro has been measured. Compound 14 interacts selectively with the GABA receptors but less effectively than isonipecotic acid and the cis-isomer 22. Compounds 4, 18, and 20 are inhibitors of the GABA uptake system, although much weaker than nipecotic acid and (3RS,4SR)-4-hydroxypiperidine-3-carboxylic acid (21). Compound 10 is inactive in both test systems.

The bicyclic 3-isoxazolol amino acids (RS)-3-hydroxy-4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridine-4-carboxylic acid (5, 4-HPCA) and (RS)-3-hydroxy-4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridine-6-carboxylic acid (11, 6-HPCA) were synthesized as model compounds for studies of the structural requirements of central excitatory amino acid neurotransmitter receptors. 4-HPCA was synthesized via introduction of a methoxycarbonyl group into the 4-position of the lithiated N-nitroso intermediate 1. The key reaction in the synthesis of 6-HPCA is an intramolecular N-alkylation of the appropriately substituted acetamidomalonate derivative 7 using sodium hydride as a base. On the basis of the pKA values for 4-HPCA the existence of an intramolecular hydrogen bond in the zwitterionic form of this amino acid is proposed. 6-HPCA was shown by 1H NMR spectroscopy to adopt preferentially a conformation with the carboxylate group in an equatorial position. 4- and 6-HPCA were tested as agonists and antagonists at excitatory amino acid receptors on neurones in the cat spinal cord using microelectrophoretic techniques. Neither compound showed significant effects at these receptors.

The bicyclic 5-isoxazolol zwitterions 4,5,6,7-tetrahydroisoxazolo[4,3-c] pyridin-3-ol (3, iso-THPO), 5,6,7,8-tetrahydro-4H-isoxazolo [4,3-c]azepin-3-ol (12, iso-THAO), and 5,6,7,8-tetrahydro-4H-isoxazolo [3,4-c]azepin-3-ol (13, iso-THIA), which are structurally related to the glycine antagonist 5,6,7,8-tetrahydro-4H-isoxazolo[3,4-d]azepin-3-ol (iso-THAZ), have been synthesized and tested biologically. All of these compounds were glycine antagonists approximately equipotent with iso-THAZ during microelectrophoretic ejection near cat spinal neurons. In contrast to iso-THAZ, which also interacts with 4-aminobutyric acid (GABA) receptors in rat brains, neither 12 nor 13 show any significant affinities for GABA binding or uptake mechanisms in vitro. The glycine antagonist 3 was, however, shown also to be a moderately potent inhibitor of GABA uptake. The structure of 12 was established by an X-ray analysis. The bond lengths of the 5-isoxazolol anionic moiety of 12 are in agreement with a pronounced delocalization of the negative charge of this compound.

Thermolysis of 3,5,7-triphenyl-1,2(4H)-diazepine (1) gives, besides the known 2,4,6-triphenyl-pyridine (2), 3,5,6-triphenyl-1,2(4H)-diazepine (3) and 3,5,6-triphenyl-1,2(1H)-diazepine (4) whose str...

The molecular adhesion layers studied in this work are comprised of symmetrical dialkoxy-substituted aromatics of the anthracene and biphenyl type, selected for their chemical and structural properties, i.e. 2,6-bis(octyloxy)anthracene, 2,6-bis(dodecyloxy)anthracene, 4,4′-bis(decyloxy)biphenyl and 4,4′-bis(hexadecyloxy)biphenyl. The characterization of these physisorbed monolayers is presented, and we propose plane-filling packing structure models for the 2D crystals. The models are based on sub A calibrated images of the reproducibly scanned adhesion layers. The molecular 2D crystals formed yield domains of varying sizes.

An improved method for preparation of 1,5-dilithio-4,8-dimethoxynapthalene have been developed, and some naphthalene based donormolecules have been prepared.

A number of new chiral binaphthol (BN) derivatives with different substituents in the 6,6'-positions in open and bridged forms have been synthesized. Their possible liquid crystalline properties and their helical twisting power (B) of three different nematic liquid crystals (LCs) were investigated. Derivatives with spatially extended substituents in the 6,6'-positions (e.g. styryl or vinil) show unusual high helical twisting power (up to 120 μm–1). A direct correlation between the magnitude of β and the length of the substituents was found.From the different temperature dependence of β of the open and bridged BNs, a molecular model was developed relating the molecular conformation and twisting power