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Hydroxy Moieties (hydroxy + moiety)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Development of Ketoside-Type Analogues of Trehalose by Using ,-Stereoselective O-Glycosidation of Ketose

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2007
Rie Namme
Abstract The stereoselective synthesis of ketoside-type analogues of trehalose is described. O-Glycosidation of hept-2-ulopyranose with trimethylsilyl ,-pyranoside promoted by trimethylsilyl trifluoromethanesulfonate afforded ,-ketopyranosyl ,-aldopyranosides exclusively. ,-Ketopyranosyl ,-aldooyranosides and ,-ketopyranosyl ,-ketopyranosides were also synthesized in a similar manner. The benzyl protecting groups of the hydroxy moieties were removed by hydrogenolysis to afford fully deprotected trehalose analogues.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

The crystal structure of perdeuterated methanol hemiammoniate (CD3OD·0.5ND3) determined from neutron powder diffraction data at 4.2 and 180,K

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2010
A. D. Fortes
The crystal structure of perdeuterated methanol hemiammoniate, CD3OD·0.5ND3, has been solved from neutron powder diffraction data collected at 4.2 and 180,K. The structure is orthorhombic, space group Pn21a (Z = 4), with unit-cell dimensions a = 12.70615,(16), b = 8.84589,(9), c = 4.73876,(4),Å, V = 532.623,(8),Å3 [,calc = 1149.57,(2),kg,m,3] at 4.2,K, and a = 12.90413,(16), b = 8.96975,(8), c = 4.79198,(4),Å, V = 554.656,(7),Å3 [,calc = 1103.90,(1),kg,m,3] at 180,K. The crystal structure was determined by ab initio methods from the powder data; atomic coordinates and isotropic displacement parameters were subsequently refined by the Rietveld method to Rp, 2% at both temperatures. The crystal structure comprises a three-dimensionally hydrogen-bonded network in which the ND3 molecules are tetrahedrally coordinated by the hydroxy moieties of the methanol molecule. This connectivity leads to the formation of zigzag chains of ammonia,hydroxy groups extending along the c axis, formed via N,D···O hydrogen bonds; these chains are cross-linked along the a axis through the hydroxy moiety of the second methanol molecule via N,D···O and O,D···O hydrogen bonds. This `bridging' hydroxy group in turn donates an O,D···N hydrogen bond to ammonia in adjacent chains stacked along the b axis. The methyl deuterons in methanol hemiammoniate, unlike those in methanol monoammoniate, do not participate in hydrogen bonding and reveal evidence of orientational disorder at 180,K. The relative volume change on warming from 4.2 to 180,K, ,V/V, is + 4.14%, which is comparable to, but more nearly isotropic (as determined from the relative change in axial lengths, e.g.,a/a) than, that observed in deuterated methanol monohydrate, and very similar to what is observed in methanol monoammoniate. [source]

Fluorometric Investigation of the Acid-Base and Complexation Behaviour of Tetracycline and Oxytetracycline

CHINESE JOURNAL OF CHEMISTRY, Issue 2 2004
Hong-Xia Li
Abstract The widely used antibiotics tetracyclines have been effectively used for ailing heart attack, ulcer cure and gene therapy. The actual mechanism of their activity has been proposed to link with the complexes with many metal ions. However, the sites at which complex formation takes place are not well established. In the present work, the deprotonation sequence of tetracycline (TC) and oxytetracycline (OTC), and their specific group used to bind europium ion were investigated by examining the character of fluorescence of TC and OTC as well as that of their complexes. It was concluded that the site of complexation is coordinated with the deprotonation sequence changing with the acidity/basicity of the solution. And it was inferred that five hydrogens in TC and OTC could be dissociated. The deprotonation sequence is as follows: C(3) hydroxy, C(10) phenol, C(4) dimethylamine, C(12) hydroxy and C(12a) hydroxy. The corresponding complexation site changed with pH increase in solution as follows: C(2) acylamino and C(3) hydroxy moiety, C(10)-C(11) ketophenol moiety, C(4) dimethylamine and C(3) hydroxy moiety, C(11)-C(12) ,-diketone moiety, C(12) hydroxy and C(12a) hydroxy moiety, and C(12) hydroxy and C(1) ketone moiety respectively. [source]