Ethyl Acetate Molecules Research Articles

Structural studies on the biosides of Digitalis lanata: bisdigitoxosides of digitoxigenin, gitoxigenin and digoxigenin.

The crystal structures and conformations of bisdigitoxosides of digitoxigenin (I), gitoxigenin (II) and digoxigenin (III and IV) have been determined using single-crystal X-ray crystallographic techniques. Crystals of (I), (II) and (IV) were grown from ethyl acetate solutions of the glycosides while (III) was grown from a solution of the digitoxoside in ethanol. As in other cardiac glycosides the ring junctions A-B and C-D are cis. The D ring in these structures shows different conformations while the A, B and C rings remain conformationally similar. Although digitoxigenin bisdigitoxoside and gitoxigenin bisdigitoxoside differ from each other in the absence and presence of a hydroxyl group at C(16) of the D ring, these two biosides crystallize in the space group P2(1)2(1)2 [corrected] and are isomorphous. The presence of the hydroxyl group at C(16) does not affect the orientation of the lactone ring and the conformation of the molecule. Digoxigenin bisdigitoxoside crystallizes in two different crystal systems with four molecules of water in the orthorhombic form and one molecule of ethyl acetate in the triclinic form. In both forms the hydroxyl at C(3') of the first sugar forms a hydrogen bond with the ring oxygen of the second sugar. This has also been observed in the trioside digoxin. The torsion angle C(13)-C(17)-C(20)-C(22) in the two forms differs by 7 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)

Structure of Ethyl Hydrogen P(R), 5′-Anhydro-2′,3′-O-Isopropylidene-Adenosine-8-Phosphonate Hemiethylacetate Solvate

Abstract The crystal, and molecular structure of the title compound [8,5′-P-cyclo-A(R)] was determined by the X-ray diffraction method. It crystallizes in space group C2221 with unit-cell dimensions a=14.222(3), b=13.879(4), c=43.612(8) A. There are two 8,5′-P-cyclo-A(R) molecules and one ethyl acetate molecule per asymmetric unit. The two cyclonucleosides have a very similar overall conformation; the glycosidic torsion angle is in the anti range, the hetero-cyclic ring between the base and sugar moieties being in the endo form, while the sugar ring conformation is C(3′)-exo. The two independent cyclo-nucleoside molecules form a hydrogen bonded dimer N(1)—H-N(6) [3.07(2) A] and N(6)-H—O(6)(the free oxygen atom of the phosphonate group) [2.99(2) A].

2?1 Complex of desoxycholic acid and ethyl acetate: Disorder in the structure at 298 and 163 K

The crystal structure of the 2∶1 channel complex of desoxycholic acid and ethyl acetate has been investigated at 298 and 163 K. The space group isP212121(No. 19) with four molecules of desoxycholic acid in the unit cell. The ethyl acetate molecules are enclathrated along the 21 axes parallel toc and exhibit differing degrees of disorder in the low- and room-temperature structures. Differences in the disorder imply that it is both statistical and dynamic in nature. Our best model for each structure yieldsR=0.064 [R w =0.058,w=(σ 2 F)−1] andR=0.068 [R w =0.064,w=(σ 2 F) −1 ] for the ambient- and low-temperature studies respectively.

The crystal structure of methyl 3,4-O-isopropylidene-2,6-di-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d-galactopyranoside at 97 K

The crystal structure of methyl 3,4-O-isopropylidene-2,6-di-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-α-d-galactopyranoside (1), C38H54O24 · (C4H8O2)0.32 was determined by X-ray diffraction;1 crystallises in space group P21 with a = 12.480(3), b = 8.821(3), c = 21.182(4)Å, β = 98.46(3)°, and Z = 2. The structure was solved by Patterson-search and Fourier-recycling procedures and refined to Rw(R) = 0.048(0.063), using 4348 [3112 with I> 2σ(I)] independent reflections. The β-d-galactosyl rings are slightly distorted and, due to the isopropylidene group, the α-d-galactoside ring is severely distorted. The conformation near the β-(1→6) and β-(1→2) linkages between the pyranoid rings is not significantly affected by the acetyl groups, but the anomeric C-O-C bridge angles have unusual values. The C-6O-6 bond in the β-d-galactosyl group (1→2)-linked to the α-d-galactoside residue has an unusual gauche—trans conformation with respect to C-4 and O-5. The CH3-(C = O)-O-C moieties are planar within 0.01Å, and 32.6% of all unit cells contain a molecule of ethyl acetate.

2:1 Adduct of colchiceine acetate and ethyl acetate

C23H25NO7.1⁄2C4HsO2, M r = 471.49, is o r t h o r h o m bic, P212121, with a = 9.299 (3), b = 10.534 (4), c = 27.084 (6) A, V = 2653 (4) A 3, z = 4, 2(Mo Ka) = 0.71069 A, D c = 1.180, D m -1.16 (2) Mg m -3. The structure was solved by the Patterson search approach where the molecular structure of isocolchicine was used as the search model and refined by full-matrix leastsquares methods. The final R value was 0.077 for 1552 observed reflections. The ethyl acetate molecule shows an occupation factor of 0.5, and the acetamido O atom is disordered. The position of the acetoxy group in the solid state defines the molecule as belonging to the isocolchicine series. The conformation of colchiceine acetate may explain its lack of accessibility at the tubulin binding site and therefore its decreased biological activity.

Infrared study of the adsorption of ethyl cyanoacetate on silica immersed in carbon tetrachloride

Infrared spectra are reported of silica immersed in solutions of ethyl cyanoacetate in carbon tetrachloride. The surface–adsorbate interaction for silica which had been preheated at 1073 K involved the formation of hydrogen bonds between pairs of isolated surface silanol groups and both the cyano and carbonyl groups in each adsorbed ethyl cyanoacetate molecule. For silica which had been evacuated at 298 K adjacent interacting surface silanol groups also provided sites for the adsorption of ethyl cyanoacetate. The adsorbed molecules were again bonded to the surface via both their cyano and carbonyl groups. Each carbonyl group was involved in a hydrogen bonding interaction with a single surface silanol group. This contrasts with the observation that pairs of adjacent interacting silanol groups each formed two hydrogen bonds with the carbonyl oxygen atom of a single ethyl acetate molecule adsorbed on silica immersed in carbon tetrachloride.

ChemInform Abstract: INFRARED STUDY OF THE ADSORPTION OF ETHYL ACETATE ON SILICA IMMERSED IN CARBON TETRACHLORIDE

The adsorption of ethyl acetate onto silica immersed in carbon tetrachloride has been studied by infrared spectroscopy. For silica which had been preheated at 863 K adsorption involved the formation of hydrogen bonds between isolated surface silanol groups and the oxygen atoms of carbonyl groups in ethyl acetate molecules. For silica preheated at 453 K the existence of other types of hydroxyl group on the oxide surface did not affect the adsorption of ethyl acetate onto isolated silanol group sites. However, a second mode of adsorption involved the formation of hydrogen bonds between pairs of adjacent hydroxyl groups and single ethyl acetate molecules. The adsorption of ethyl acetate onto pair sites constituted a stronger mode of adsorption than that involving single silanol groups and was particularly significant at low surface coverages.

Infrared study of the adsorption of ethyl acetate on silica immersed in carbon tetrachloride

The adsorption of ethyl acetate onto silica immersed in carbon tetrachloride has been studied by infrared spectroscopy. For silica which had been preheated at 863 K adsorption involved the formation of hydrogen bonds between isolated surface silanol groups and the oxygen atoms of carbonyl groups in ethyl acetate molecules. For silica preheated at 453 K the existence of other types of hydroxyl group on the oxide surface did not affect the adsorption of ethyl acetate onto isolated silanol group sites. However, a second mode of adsorption involved the formation of hydrogen bonds between pairs of adjacent hydroxyl groups and single ethyl acetate molecules. The adsorption of ethyl acetate onto pair sites constituted a stronger mode of adsorption than that involving single silanol groups and was particularly significant at low surface coverages.

The structure of o-bromocarbobenzoxy-glycyl-L-prolyl-L-leucyl-glycyl-L-proline ethyl acetate monohydrate: a substrate of the enzyme, collagenase

The crystal and molecular structure of a synthetic oligopeptide, o-bromocarbobenzoxy-glycyl-prolylleucyl-glycyl-proline ethyl acetate monohydrate, has been established by the X-ray diffraction method. The monoclinic crystal belongs to the space group P21 with Z=2. Cell dimensions are a= 13710, b= 14.007, c= 10.861 ~ and fl= 114.60 °. As in the case of p-bromocarbobenzoxy-glycyl-prolyl-leucylglycine(tetrapeptide), the peptide chain is folded back at the Pro(l) and Leu residues to form two intramolecular hydrogen bonds between two glycine residues. This folding conformation (called 'or-Ufolding' in this paper) is almost identical to that in the tetrapeptide. This conformation is found in other oligopeptides and also in some protein structures; hence, it is understood to be one of the specific and stable conformations, in contrast with that proposed for the collagen molecule. In relation to this conformation, the 'fl-U-folding' conformation is also discussed. In the crystal structure, intermolecular hydrogen bonds are observed between the peptide bonds of Pro(1)-Leu residues via the water molecule. The ethyl acetate molecule is in the hydrophobic environments. Generally speaking, intermolecular interaction is weak in this crystal, which is consistent with the lower density of the crystal compared with that of tetrapeptide.