Chemistry of 1,3-Dioxepins. XIV.1 Structural Studies of 4,7-Dihydro-(4,7-dihydro-1,3-dioxepin-2-yl)-1,3-dioxepin and Their Metal Complexes

The coordination properties and conformational behaviour of 4,7- dihydro-(4,7-dihydro-1,3-dioxepin-2-yl)-1,3-dioxepin 1, bis-(1,3-dioxepin), or C10H14O4 have been investigated. The crystal and molecular structures of bis-(1,3-dioxepin) (1), bis-(1,3-dioxepin) lithiumperchlorate (2:1) (2) and bis-(1,3-dioxepin) sodium-perchlorate (1:1) (3) complexes, as well as bis-(1,3-dioxepin) hexsaaquamagnesiumperchlorate (3:1) chlatrate (4), have been determined by X-ray diffraction. The molecule of bis-(1,3-dioxepin) is a bidentate ligand in mononuclear lithium complex 2, in contrast to its bridging mode in 2D polymeric sodium complex 3. The coordination environment around lithium in 2 is distorted octahedral with C2 symmetry, while around sodium in 3 it is quasi-pentagonal bipyramidal. Out of four possible conformations of bis-(1,3-dioxepin) molecule, twist-boattwist- boat centrosymmetric (tb-tb-c), twist-boat-twist-boat non-centrosymmetric (tb-tb), twist-boat-chair (tb-ch) and chair-chair (ch-ch), three have been found in the investigated crystal structures: ch-ch in 1, tb-tb in 2 and tb-tb-c in 3 and 4

A New Stereoselective Route to Preparing Optically Active 2-Imino-penam Derivatives

A novel and simple procedure for preparation of (5R,6S)-2-ben- zylimino-6-bromo-3-isopropylidene-penam 2 and (oR,6Sj-2-benzyl- imino-3-isopropylidene-penam 8 is described. The 2-imino-penam derivatives are prepared by modification of the Cooper reductive rearrangement of 3a-benzylamide of penicillanic acid sulfoxides. The absolute configurations of starting sulfoxides and imino-prod- ucts are assigned on the basis of 1H-NMR spectroscopic studies and verified by X-ray structure analysis of sulfoxide 3b and imino- penam 8

Chemistry of 1,3-Dioxepins. XVI.1 The Synthesis, Characterization and Crystallographic Analysis of Some Arylsulphanyl-, Arylsulphinyl-, Arylsulphonyl- and Benzoyl- N-Substituted Derivatives of 1a,2,6,6a-Tetrahydro-1H,4H-[1,3]dioxepino[5,6-b]azirines

Chemo-selective synthesis and characterization of N-[(4-nitrophenyl)sulphanyl]- 2 and N-[(4- nitrophenyl)sulphinyl]- 3 N-[(4-aminophenyl)sulphonyl]- 5 and N-(4-aminobenzoyl)- 7 derivatives of 1a,2,6,6a-tetrahydro-1H,4H-[1,3]dioxepino[5,6-b]azirines, starting from 1a,2,6,6a-tetrahydro-1H,4H-[1,3]dioxepino[5,6-b]azirine (1), are described. Their solid state conformational behaviour based on crystallographic analysis shows that: (i) dioxepinoazirine moiety of 2, 5 and 7 adopts a boat-chair (BC) conformation, while dioxepinoaziridine moiety of 3 adopts a twistboat (TB) conformation; (ii) the substituent on aziridine nitrogen is always in trans and never in cis position in relation to the dioxepane ring; (iii) the orientation of sulphanyl-, sulphinylsulphonyl- and carbonyl- moiety in 2, 3, 5 and 7 are defined by torsion angles C1-S1-N1-C7 of 110.7(2)°, 82.6(2)°, 88.80(11)°and C1-C-N1-C7 of 64.9(5)°, respectively; (iv) Phenyl moiety of sulphinyl and sulphonyl derivatives, 3 and 5, is perpendicular to the S-N bond with the torsion angles N1-S1-C1-C2 of 67.9(3)° and –92.54(13)°, respectively, while that of sulphanyl- 2 and carbonyl- 7 derivatives is coplanar to S-N or C-N bonds with the torsion angles N1-S1-C1-C2 and N1-C-C1-C2 of 168.5(2)° and 170.9(4)°, respectively. Obtained data will serve for further investigation of steric and electronic properties of studied compounds aimed at designing antihyperglycaemically more potent analogues

Synthesis of Novel, Potentially Biologically Active Dibenzosuberone Derivatives

Novel representatives of the important group of biologically active dibenzosuberone derivatives were prepared, 3, 7-dibromo-5-(dimethylaminoethyl-oxyimino)-10, 11-dihydro-5H-dibenzo[a, d]cyclohepta-1, 4-diene (1), 3, 7-dibromo-5-(3-dimethylaminopropylidene)-10, 11-dihydro-5H-dibenzo[a, d]cycloheptene (2) and 1, 7-dibromo-5-(3-dimethylaminopropylidene)-10, 11-dihydro-5H-dibenzo[a, d]cycloheptene (3). These compounds are potential members of tricyclic antidepressants (TCAs), still in many countries the most frequently prescribed antidepressants

Chemistry of 1,3-Dioxepins. X. Regio and Stereocontrolled Syntheses of Antihyperglycemic N-Sulfonyl-1a,2,6,6a-tetrahydro-1H,4H[1,3] -dioxepino[5,6-b]azirines via Isomeric cis- and trans- Sulfonamidodioxepanols

Regio- and stereocontrolled syntheses of 1-sulfonyl-1a,2,6,6a-tetrahydro-1H,4H[1,3] -dioxepino[5,6-b]azirine 1, the lead compound of a novel class of potent antihyperglycemics, via isomeric cis- and trans-sulfonamidodioxepanols 6 and 13 are described. The constitution and configuration of the key intermediates 6 and 13 were elucidated by independent syntheses and confirmed by the X-ray structure analysis

Chemistry of 1,3-Dioxepins. XII.\u27 4,7-Dihydro-5-nitro-1,3-dioxepins in the Diels-Alder Reaction with 4-Methyloxazole

4,7-Dihydro-5-nitro-l,3-dioxepins 4\u27 prepared by dehydrohalogenation of vic-chloronitro-dioxepanes 2 and/or dehydrohalogenationdemercuration of vic-chloromercurynitro-dioxepanes 3 represent reactive dienophiles in the Diels-Alder cycloaddition with 4-methyloxazole (5), giving pyridoxine (8) intermediates 1,5-dihydro-9-hydroxy- 8-methyl-3H-[1,3]dioxepino[5,6-c]pyridines 6 in poor yields. The side products of this reaction were 4,7-dihydro-4-hydroxyimino- 6-nitro-l,3-dioxepins 7, the structure of which was confirmed by parallel synthesis, i.e. by nitrosation of 4 with ethyl nitrite. The order of reactivity in the series of 5-substituted-4, 7-dihydro- 1,3-dioxepins, calculated by AMI semiempirical method, is predicted to be 5-nitro- > 5-unsubstituted- > 5-cyano- > 5-chloro-4,7-dihydro- 1,3-dioxepin, and it is in agreement with experimental data

Scope and limitations of sodium and potassium trimethylsilanolate as reagents for conversion of esters to carboxylic acids

Sodium or potassium trimethylsilanolate act as versatile and very powerful reagents for conversion of a wide variety of esters to carboxylic acids. The reactions were performed in tetrahydrofuran under mild reaction conditions with high to quantitative yields

Methionine Adenosyltransferase Purified from Rat Liver

Methionine adenosyltransferase (MAT III), also known as S-adeno-sylmethionine synthetase, was purified from rat liver and crystallized. X-ray diffraction data were collected using a microfocused synchrotron radiation. The crystallization conditions were extensively optimized but final crystal size was never larger than 303 pm3. Due to their small size crystals had no detectable diffraction on either rotating anode source or the Deresbury SRS beamline 9.6 (GB). Finally, four data sets were collected on Grenoble ESRF (France) undulator microfocus beamline ID13 to resolution of 3.2-3.6 Å. Crystals belong to the cubic space group F432 with cell dimension a = 246 Å. Attempts are under way to solve the structure by molecular replacement, using recombinant MAT I rat liver structure as a search model

Conformational Behaviour of 11-O-Methylazithromycin in the Solid and Solution State

Conformational behaviour of azithromycin 11-OMe derivative 2 (Scheme 1) has been studied in the solid and solution state. In the CDCl3 and DMSO solution, 2 mainly adopts the »folded-in« conformation. 11-OMe group is oriented toward the centre of aglycone ring. The crystal structure of DMSO solvate of 2 has been solved by the molecular replacement method using the solution state conformation as the search model. Conformation of 2 in the solid and solution state is very similar. Molecules of 2 are held together in the crystal by van der Waals interactions, forming a solvent channel along the b axis. The DMSO molecule is found to be disordered and bound to cladinose moiety of 2 by H-bond O4"-H...01s

4-Acetamido-N-(λ5-triphenyl­phospho­ranyl­idene)benzene­sulfonamide

There are two independent mol­ecules per asymmetric unit of the title compound, C26H23N2O3PS. Their superposition shows that they differ in the conformation of the CH3CO– group and the benzene rings from the triphenyl­phospho­rane group. In the crystal structure, independent mol­ecules are inter­conected by strong N—H⋯O hydrogen bonds, forming infinite chains along the a axis