ChemInform Abstract: NONTEMPLATE SYNTHESIS OF ′N4′ MACROCYCLIC IMINE LIGANDS WITH VARIABLE RING SIZES: THE IMPORTANCE OF INTRAMOLECULAR HYDROGEN BONDING. X-RAY CRYSTAL STRUCTURES OF THREE MACROCYCLIC AND TWO OPEN-CHAIN LIGANDS

1981 ◽  
Vol 12 (18) ◽  
Author(s):  
P. G. OWSTON ◽  
R. PETERS ◽  
E. RAMSAMMY ◽  
P. A. TASKER ◽  
J. TROTTER
1986 ◽  
Vol 39 (10) ◽  
pp. 1559
Author(s):  
PR Andrews ◽  
V Cody ◽  
MN Iskander ◽  
AI Jeffrey ◽  
MF Mackay ◽  
...  

Two multisubstrate analogues of the transition state in the reaction catalysed by the enzyme GABA- transaminase (E.C. 2.6.1.19), sulfonic acid pyridoxal dervative , C10H16N2O5S (1) and carboxylic acid pyridoxal derivative, C13H18N2O4 (2), have been characterized by X-ray analyses of crystals of (1). HCl , (1).H2O and (2). HCl . In each structure, the nitrogen on the side chain is the donor in intramolecular hydrogen bonding. However, it is only in (2). HCl that this interaction is with the phenolic oxygen as postulated in the proposed transition state of the reaction catalysed by GABA- transaminase . For both structures of (1), on the other hand, this interaction is with the oxygen of the ring hydroxymethyl substituent, and results in a seven- membered ring. Conformational analysis indicates that both modes of hydrogen bonding may be present in the pyridoxal derivatives, although no quantitative assessment is possible at the MINDO/3 or MNDO levels. Simple classical potential energy calculations indicate significant structural differences between the lowest energy conformations of these compounds and the calculated transition state. However, conformations which match the key features of the transition state are also relatively low in energy.


1989 ◽  
Vol 42 (7) ◽  
pp. 1103 ◽  
Author(s):  
CO Miles ◽  
L Main ◽  
BK Nicholson

Two improved general routes to 2′,6′-dihydroxychalcones are described in which the final step is protective-group removal from O 2′ under mild acid conditions. The first involves base-catalysed condensation of benzaldehydes with 2′-hydroxy-6′-tetrahydropyran-2-yloxyacetophenone, the second ring-opening of 5-hydroxyflavanones with 1,8-diazabicyclo[5.4.0]undec-7-ene in the presence of a trialkylchlorosilane to trap out the chalcone as a bis silyl ether. Chalcones prepared by the first route are 2',6'-dihydroxychalcone (1), and its 4-methoxy (2), 3,4-dimethoxy (3), 3,4,5-trimethoxy (4), and 2,4,6-trimethoxy (5) derivatives. The 4-chloro derivative (6) and the chalcone from hesperetin are prepared by the second method. .The X-ray crystal structure of 2',6'-dihydroxy-2,4,6-trimethoxychalcone (5), the first for a 2',6′-dihydroxychalcone, is reported, the hydrogen involved in intramolecular hydrogen-bonding between the carbonyl and phenolic oxygens being located for the first time for any 2'-hydroxychalcone derivative. The O 6' involved in the intramolecular hydrogen-bonding is also hydrogen-bonded intermolecularly to the hydrogen of the other (2'-)hydroxy group of a neighbouring molecule in the lattice. 13C n.m.r. data are the first reported for a series of 2',6'-dihydroxychalcones.


2015 ◽  
Vol 71 (9) ◽  
pp. 768-775
Author(s):  
Hendrik Klien ◽  
Wilhelm Seichter ◽  
Konstantinos Skobridis ◽  
Edwin Weber

Having reference to an elongated structural modification of 2,2′-bis(hydroxydiphenylmethyl)biphenyl, (I), the two 1,1′:4′,1′′-terphenyl-based diol hosts 2,2′′-bis(hydroxydiphenylmethyl)-1,1′:4′,1′′-terphenyl, C44H34O2, (II), and 2,2′′-bis[hydroxybis(4-methylphenyl)methyl]-1,1′:4′,1′′-terphenyl, C48H42O2, (III), have been synthesized and studied with regard to their crystal structures involving different inclusions,i.e.(II) with dimethylformamide (DMF), C44H34O2·C2H6NO, denoted (IIa), (III) with DMF, C48H42O2·C2H6NO, denoted (IIIa), and (III) with acetonitrile, C48H42O2·CH3CN, denoted (IIIb). In the solvent-free crystals of (II) and (III), the hydroxy H atoms are involved in intramolecular O—H...π hydrogen bonding, with the central arene ring of the terphenyl unit acting as an acceptor. The corresponding crystal structures are stabilized by intermolecular C—H...π contacts. Due to the distinctive acceptor character of the included DMF solvent species in the crystal structures of (IIa) and (IIIa), the guest molecule is coordinated to the hostviaO—H...O=C hydrogen bonding. In both crystal structures, infinite strands composed of alternating host and guest molecules represent the basic supramolecular aggregates. Within a given strand, the O atom of the solvent molecule acts as a bifurcated acceptor. Similar to the solvent-free cases, the hydroxy H atoms in inclusion structure (IIIb) are involved in intramolecular hydrogen bonding, and there is thus a lack of host–guest interaction. As a result, the solvent molecules are accommodated as C—H...N hydrogen-bonded inversion-symmetric dimers in the channel-like voids of the host lattice.


1996 ◽  
Vol 49 (7) ◽  
pp. 775 ◽  
Author(s):  
TW Hambley ◽  
TW Hambley ◽  
KG Lewis ◽  
KG Lewis ◽  
DJ Tucker ◽  
...  

Reaction of olean-12-ene-3β,16β,22α,28-tetrol ( chichipegenin ) (1) with methyl orthoformate gives the 16β,22α,28-orthoformate (2). Acetylation of the ortho ester followed by hydrolysis gives the tetrol 3β-monoacetate (5). It is shown that intramolecular hydrogen bonding occurs in the tetrol (1) and the 3β-monoacetate (5) in non-polar solvents. X-Ray crystallographic data on the tetrol and its tetraacetate (4) are reported. The tetrol,C30H50O4, M 474.72, crystallized in the orthorhombic space group P 212121 with a 12.363(6), b 31.888(3), c 6.962(3) Ǻ, V 2745(1) Ǻ3, Dc(Z = 4) 1.149 g cm-3, N = N(unique) 2394, No 1878 [I > 1.5σ(I)], Nvar 500; R 0.038, Rw 0.040. The tetraacetate , C38H58O8, M 642.87, crystallized in the monoclinic space group P 21, with a 10.603(2), b 16.569(1), c 10.814(1) Ǻ, β 98.72(1)°, V 1877.9(4) Ǻ3, Dc(Z = 2) 1.137g cm-3 N 3090, Rmerge 4.67% for N(unique) 2917, No 2663 [I > 2.5σ(I)], Nvar 414; R 0.053, Rw 0.050.


1996 ◽  
Vol 49 (11) ◽  
pp. 1251
Author(s):  
CF Carvalho ◽  
DP Arnold ◽  
RC Bott ◽  
G Smith

The crystal structure of the asymmetric 1,3-diol 1,1-diphenylbutane-1,3-diol has been determined and refined to a residual R of 0.039 for 795 observed reflections. Crystals are orthorhombic, space group P212121, with four molecules in a cell of dimensions a 9.625(4), b 16.002(3), c 8.834(3) Ǻ. The compound is unique among the known crystallographically characterized open-chain 1,3-diols in having only intramolecular hydrogen bonding involving the hydroxy groups [O-- -O 2.602(5) Ǻ].


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