Paolo Domiano

Conformational behaviour and E/Z isomerization of N-acyl and N-aroylhydrazones

Abstract The stereochemical behaviour of N -acyl and N -aroylhydrazones of aromatic aldehydes, of pyruvates and of acetone, in polar and less polar solvents, has been studied by HPLC and by NMR techniques. Z/E Geometrical isomers and cis / trans amide conformers have been found for N -acylhydrazones, while for N -aroylhydrazones only geometrical isomers were detected. Energy barriers of isomers are reported, and solvent effects are discussed with regard to hydrogen bond interactions.

Aroylhydrazones as chelating agents: d10-metal complexes of pyridine-2-carbaldehyde salicyloylhydrazone and x-ray structure of the zinc derivative

Abstract The title organic ligands (Hsip) gave, by reaction with d10-metal acetates, complexes of the type M(sip)2 (M = Zn, Cd, Hg), in which the ligand behaved as terdentate, producing a distorted octahedral environment around the metal. The 1H and 13C chemical shifts found for these complexes in DMSO are compared with the corresponding ones of the free ligand. The crystal structure of the zinc derivative has been determined from diffractometer data to R = 0.072 for 1086 independent reflections. Crystals are monoclinic, space group C2/c, with unit-cell dimensions a = 18.193(2), b = 24.532(6), c = 11.535(2) A,β = 103.71(1)° and Z = 8. Coordination occurs through the carbonyl oxygens (Zn−O = 2.10, 2.16(1) A), the azomethine nitrogens (Zn−N = 2.04, 2.07(1) A) and the pyridine nitrogen s(Zn−N = 2.24, 2.26(1) A).

Molecular inclusion in functionalized macrocycles. Part 9. The crystal and molecular structure of p-t-butylcalix[4]arena–anisole (2 : 1) complex: a new type of cage inclusion compound

p-t-Butylcalix[4]arene (1a), the cyclic tetramer obtained by the condensation of p-t-butylphenol and formaldehyde, crystallizes from anisole forming a new type of cage inclusion compound with the solvent. Crystals having a 2 : 1 host–guest stoicheiometry are tetragonal, space group P4/n, a=b= 12.823(6); c= 25.618(8)A, Z= 2, final R values 0.073. Two molecules of the macrocycle, in the cone conformation, face the methyl groups of the para-substituents creating a closed cavity which encapsulates one molecule of anisole. The guest is disordered in the cavity in at least eight equivalent orientations.

Hydrogen bonding in thiosemicarbazide

In a recent paper (Domiano, Fava Gasparri, Nardelli & Sgarabotto, 1969, DGNS) the crystal-structure analysis of thiosemicarbazide, carried out by photographic methods, was reported (final R=9 .9%) . The positions of the hydrogen atoms were postulated from consideration of the hybridization of the nitrogen atoms and the packing interactions, no direct determination of position being possible from the final difference synthesis. In order to obtain a more accurate structure analysis, suitable for the location of the hydrogen atoms, new data have been collected at room temperature with an automated Picker diffractometer.

Auxin structure and activity on tomato morphogenesis in vitro and pea stem elongation

In order to understand better the relationship between auxin structure and activity on morphogenesis and cell elongation, six different auxins were tested on the regeneration of tomato (Lycopersicon esculentum Miller var. Alice) from cotyledons and on pea (Pisum sativum L. var. Alaska) stem elongation. The auxins were: indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), 1, 2-benzisoxazole-3-acetic acid (BOA), 1,2-benzisothiazole-3-acetic acid (BIA), 1-naphthalenacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D). All these compounds obey the minimum requirement rules for auxin activity and all were effective on cell elongation. At the dose of 10 μM and in the absence of cytokinin, they all, except 2,4-D, induced roots, while in the presence of cytokinin they induced shoots, roots, hairy root-like filaments (HRLF) or callus depending on their concentration. The morphogenetic pattern did not change by varying cytokinin concentration. We conclude that auxin structure plays a minor role in morphogenesis or cell elongation, because it is only responsible for variations in the level of auxin activity.

3-(4-iodomethyl-2-oxo-1-azetidinyl)propynoic acidt-butyl ester: a new β-lactam derivative, synthesis of an ynamide by reaction of 4-iodomethylazetidin-2-one with the t-butyl ester of propiolic acid in the presence of copper(i)

Abstract The reaction of 4-iodomethylazetidin-2-one (2) with the t-butyl ester of propiolic acid (4) in the presence both of equimolar amounts of copper(I) and oxygen results unexpectedly in the fomation of the β-lactam ynamide 5. Its structure was suggested by spectroscopic data and confirmed by single-crystal X-ray analysis.

Synthesis and antimicrobial properties of substituted 3-aminoxy-(E)-2-methoxyiminopropionyl penicillins and cephalosporins☆

Abstract The 3-aminoxy-( E )-2-methoxyiminopropionyl penicillins 13 and cephalosporins 14 and 15 were synthesized and assayed for their antimicrobial activity on Gram-positive and Gram-negative bacteria whether producers of β-lactamases or otherwise. Compounds 13 , 14 , and 15 exhibited an activity which was generally lower than that of the corresponding phenylacetyl derivative: penicillin G ( 4 ), cephaloram ( 5 ), and phenylacetamidodesacetoxycephalosporanic acid ( 6 ). Furthermore, the comparison of the minimum inhibitory concentration values of some of the new 2-methoxyimino 3-aminoxypropionyl derivatives 13–15 with those of the corresponding ones 1–3 lacking the 2-methoxyimino substituent showed that the introduction of the 2-methoxyimino group of E configuration on the aminoxypropionamido side chain of 1–3 gives compounds ( 13–15 ) which do not generally possess better antimicrobial properties.

Molecular inclusion in functionalized macrocycles part 10*: Crystal and molecular structure of ap-tert-butylcalix[6]arene hexapodand

Colourless prismatic crystals of (3) were obtained from ethanol/CH2Cl2 (1:1) solution, space groupP21/c,a=14.581(5),b=22.517(8),c=11.799(5) Å, β=92.13(4)°. Refinement led to a final conventionalR value of 0.074 for 4247 reflections. The conformation of the molecule, which lies on a center of symmetry, is 1,2,3-alternate with one oligoethereal chain pointing inside the molecular cavity.

Structural researches on metal complexes with ligands containing the pyridoxal moiety: X-ray structure of chloro(N-pyridoxylidene-N′-salicyloylhydrazinato) copper(II) Monohydrate

SummaryThe x-ray crystal structure of the title complex is described Crystals are monoclinic, space groupP21/n, with unit-cell dimensions:a=18.070(2),b=13.471(2),c=6.788(2) Å,β=94.70(1)∘,Z=4. The structure was solved from diffractometer data by Patterson and Fourier methods and refined by least-squares techniques toR=5.0% for 2451 independent reflections. It consists of complex molecules, in which the copper atom square planar coordination comprises the chlorine atom, Cu-Cl=2.240(3) Å, and the organic ligand which acts as terdentate through the oxygen atom [Cu-O=1.948(3) Å] and a nitrogen atom, [Cu-N=1.933(5) Å] from the hydrazidic chain and the oxygen atom, [Cu-O = 1.894(4) Å] from the pyridoxal group.

Conformationally restrained β-blocking oxime ethers: synthesis and β-adrenergic properties of diastereoisomeric anti and syn 2-(5'-isoxazolidinyl)-ethanolamines

Abstract The diastereoisomeric N -isopropyl- and N-t -butyl-substituted 2-(5′-(3′-phenyl)- and 2-(5′-(3′-isopropyl)isoxazolidinyl)-ethanolamines ( 5–8 ), which can be viewed as conformationally restrained analogs of the corresponding β-blocking oxime ethers 10 and 11 , were synthesized. The relative configurations of 5–8 were assigned by 1 H-NMR studies and by the determination of the solid-state structure of one of the new compounds ( 6a ). The new isoxazoline derivatives ( 5–8 ) were tested both by radioligand binding assays and by functional tests on isolated preparations. Compounds 5a–8a were found to retain, albeit to a lower extent, the β-blocking properties of the corresponding oxime ethers 10a and 11a , thus indicating that these last compounds may prove to be still capable of interacting with the β-receptors, even if their C = NOCH 2 portion is constrained in a conformationally semi-rigid isoxazoline structure. Possible rationalizations of the results were sought by comparing the conformations and the molecular reactivity of model compounds of the isoxazolines 5–8 and of the oxime ethers 10 and 11 .