Boat-chair Conformation Research Articles

Synthesis, conformational analysis, and antiarrhythmic properties of 7-benzyl-3-thia-7-azabicyclo[3.3.1]nonan-9-one, 7-benzyl-3-thia-7-azabicyclo[3.3.1]nonane hydroperchlorate, and 7-benzyl-9-phenyl-3-thia-7-azabicyclo[3.3.1]nonan-9-ol hydroperchlorate and derivatives: single-crystal X-ray diffraction analysis and evidence for chair-chair and chair-boat conformers in the solid state.

The synthesis of the title ketone has been completed via a type of Mannich reaction starting from 4- thianone . An X-ray diffraction analysis has revealed that the solid system is a chair-boat conformer with the sulfur atom in the boat portion of the bicyclic ring compound. Wolff- Kishner reduction of the ketone group gave 7-benzyl-3-thia-7-azabicyclo [3.3.1]nonane, which was isolated as the hydroperchlorate . However, X-ray diffraction analysis of the salt showed this solid to be a chair-chair conformer. Addition of phenylmagnesium bromide to the ketone gave a tertiary alcohol with the C-C6H5 bond being equatorial with respect to the thiane ring and axial with respect to the piperidine ring. The reaction of the Grignard reagent with the ketone to give this alcohol seems to be very stereospecific. An X-ray analysis of the hydroperchlorate of the alcohol confirmed the system to be a chair-chair form in the solid. The title compounds were screened for antiarrhythmic activity in anesthetized mongrel dogs in which myocardial infarctions had been created when the left anterior descending coronary artery was ligated. Vagal-induced slowing of the sinus mode firing rate was used to determine the underlying ventricular automaticity in the dogs, which averaged 164 +/- 27 beats/min. Ventricular pacing was initiated to rates between 240 and 390/min. This technique resulted in the induction of rapid and sustained ventricular tachycardia. At doses of 3 and 6 mg/kg of body weight, 7-benzyl-3-thia-7-azabicyclo [3.3.1]nonane hydroperchlorate in alcohol (the solution was administered intravenously) was able to suppress markedly the induced ventricular tachycardia in five of six dogs. The compound also caused a 10-15% increase in blood pressure within a few minutes. The antiarrhythmic properties of this compound and others of related structure are discussed, and some comparison is made with the action of lidocaine in similar dog preparations.

Studies of chrysanthemic acid derivatives: catalysed reactions of 3-(2-hydroxy-methyl-3,3-dimethylcyclopropyl)-2-methylpropanol and formation of a novel eight-membered cyclic sulphite

Acid catalysed reaction of the cyclopropanediol (3) derived from cis-chrysanthemic acid cis-(1) afforded, depending on the reaction conditions, 3-vinyl-2,2,5,5-tetramethyltetrahydrofuran (4) and 4,4,7,7-tetramethyl-3-oxabicyclo[4.1.0]heptane (5). On treatment with thionyl chloride–pyridine complex there was obtained in addition the eight-membered cyclic sulphite, 6,6,9,9-tetramethyl-3,5-dipxa-4-thiabicyclo[6.1.0]nonane 4-oxide (6). X-Ray analysis confirms a boat-chair conformation with the SO group trans to the cyclopropane ring and in an equatorial situation. Thermal reaction of (6) gave either (4) or a mixture of (5), cis-chrysanthemol (7), and cis-isochrysanthemol (8).

Nuclear magnetic resonance investigations of configurational non-rigidity in dinuclear platinum(IV) complexes. Part 5. Intra-molecular rearrangements in the dinuclear platinum(IV) complexes of 1,3,5,7=tetrathiocane. X-Ray Crystal Structure of [(PtClMe3)2-(SCH2SCH2SCH2SCH2)

The complexes [(PtXMe3)2(bCH2SCH2SCH2SkH2)] (X = CI, Br, or I) have been prepared by direct reaction of 183,5,7-tetrathiocane with the appropriate halogenotrimethylplatinum(iv) tetramer, [ (PtXMe,),] (X = CI, Br, or I). The X-ray crystal diffraction structure of [(PtCIMe3)2(SCH2SCH2SCH2SCH2)] shows the dimeric platinum moiety to be 1,3-co-ordinated to the ligand which has a chair-boat conformation. Low-temperature H n.m.r. spectroscopy confirms such a structure to be retained in solution for all three complexes. Lineshape changes observed in variable-temperature 1 H n.m.r. investigations are consistent with the complexes undergoing metal-pivot and platinum-methyl intramolecular rearrangements. Alternative mechanisms are discussed for both processes. It is concluded that the former comprises a series of 90" 1,5-metal pivots, and the latter, 120" rotations of methyl groups on the commuting Pt atom. Full bandshape analyses have been undertaken for both motions. Evidence is presented in support of the two fluxions being different manifestations of one transition state rather than independent rearrangements.

The structure of tanacetols A, C17H26O4, and B, C19H30O5, two new sesquiterpene alcohols from Tanacetum vulgare L.

Tanacetol A, m.p. 371 K, (a)25°c=--99 ° (CHC13, 1.0 g dm-3), is a ketol sesquiterpene isolated from a rare chemotype of Tanacetum vulgare L.: M r = 294.4, orthorhombic, P2,212 ~, a = 11.132 (4), b= 11.255 (3), c= 13.782 (4)/~, U= 1726.8 (8)A 3, Z = 4, D x = 1.13 Mg m -3, F(000) = 640, g(Mo Ka) = 0.09 mm -~, room temperature. Tanacetol B is the main constituent of the above chemotype and its monoacetyl derivative, m.p. 413K, (~t)25°c=-205 ° (CHC13, 0.4 g din-a), was investigated: M r = 338.4, orthorhom- bic, P2~2~2~, a= 7.589 (3), b= 10.997 (5), c= 23.416(9)A, U= 1954(1)A 3, Z=4, Dx= 1.14 Mg m -3, F(000) = 736, g(Mo K~t) = 0.09 mm -~, room temperature. The structures were solved by direct methods and refined to R = 0.041 for tanacetol A and to R = 0.046 for tanacetol B acetate using, respectively, 1088 and 1594 unique reflexions. Both ten-membered rings show a C(1)-C(10) trans double bond and present the energetically less favoured boat-chair conformation. The C(14) methyl and the C(15) methene are syn and on the a face of the rings; the oxygen of the keto group in tanacetol A is on the fl face whereas the C(5) acetyl group in tanacetol B acetate is on the a face. Introduction. In spite of the frequent occurrence of germacranes bearing the C(7) side chain oxidized at the *Tanacetol is 5-(2-hydroxyisopropyl)-2-methyl-8-methylene-7- oxo- 1-cyclodecen- 10-yl acetate.

Conformational study of the 1-azabicyclo[3.3.1]nonan-2-one system. Molecular-mechanics calculations and X-ray structure of 5-phenyl-1-azabicyclo[3.3.1]nonan-2-one

Molecular-mechanics calculations for 5-methyl-1-azabicyclo[3.3.1]nonan-2-one indicate that the boat–chair conformation is more stable than the twin-boat conformation by 4.0 kJ mol–1. An endo methyl substituent at position 7 causes the twin-boat conformation to be favoured by 5.2 kJ mol–1. The boat–chair conformation of 5-phenyl-1-azabicyclo[3.3.1]nonan-2-one has been characterized by X-ray crystal-structure analysis. The bridgehead amide is appreciably distorted from planarity, with N(1) displaced by 0.36 A from the plane of C(2), C(8), and C(9). The crystal structure provides an example of enantiomeric disorder: on average, each molecular site is occupied by 0.8 of a molecule of one configuration and 0.2 of the mirror-image molecule. Crystallographic data are a= 12.253(3), b= 8.372(2), c= 11.665(3)A, Z= 4, space group Pca21. X-Ray intensity measurements were made on a four-circle diffractometer and least-squares adjustment of the atomic parameters converged at R 0.050 for 1 023 reflections.

Additions and Corrections - A Chair-Boat Conformation in 2,4,6,8-Tetraphenyl-3-aza-7-thiabicyclo[3.3.1]-nonan-9-one. An X-Ray Diffraction Analysis of a Single Crystal of the Compound

Additions and Corrections - A Chair-Boat Conformation in 2,4,6,8-Tetraphenyl-3-aza-7-thiabicyclo[3.3.1]-nonan-9-one. An X-Ray Diffraction Analysis of a Single Crystal of the Compound

Über zinn-haltige heterocyclen : V. Sn-phenyk-substituierte stannocane, Übergänge von tetraedrischer 4-Zu trigonal-bipyramidaler 5-koordination

A complete series of diphenyl and mixed methyl/chlorine/bromine/iodinephenyl substituted oxadithia- and trithiastannocanes has been prepared by reactions between the respective disodium dithiolates and tin dihalides. The 13C NMR chemical shifts of these compounds and the coupling constants J( 119Sn 13C) are dependent upon the magnetic anisotropy of the substituents and the bond angles at the tin atom. The crystal structure of 2,2-diphenyl-1,3,6-trithia-2-stannocane has been determined and refined to R = 0.039. The environment of Sn is a monocapped tetrahedron (transannular distance Sn⋯S 324.6(1) pm). This type of coordination, intermediate between a tetrahedron and a trigonal bipyramid, is discussed quantitatively and compared with a series of analogous compounds. The eight-membered ring has the boat-chair conformation.

5-Chlor-5-phenyl-1-oxa-4.6-dithia-5-stannocan, ein diplanarer Übergangszustand bei der Racemisierung der Wanne-Sessel- Konformation in einem 8-Ring [1] / 5-Chloro-5-phenyl-1-oxa-4,6-dithia-5-stannocane, a Diplanar Transition State for the Racemisation of the Boat-Chair Conformation in an Eight-Membered Ring [1

Abstract The title compound has been synthesized from PhSnCl3 and the disodium salt of bis(2-mercaptoethyl)ether. The crystal structure has been determined and refined to R - 0.033. The conformation of the eight-membered heterocycle is slightly disordered and represents a diplanar form, which is generally considered the transition state near the saddle point of the energy surface between the two enantiomers of the boat-chair con-formation. The configuration around tin is a trigonal bipyramid with equatorial sulfur atoms, an equatorial phenyl group and with axial atoms Cl and O (transannular distance Sn···O 241 pm).

Synthesis and conformations of α-aminoadipyl- and glycyl-α-aminoadipylthiazepine sulfoxides

The title compounds, having the R-absolute configurations at sulfur, and labelled with 14C at carbons 5, 6, and 7 of the seven-membered ring, have been synthesized by condensation of isotopically labelled 3D-benzhydryloxycarbonyl-6L-amino-2,2-dimethyl-5-oxoperhydro-1,4-thiazepine with N-Boc- and α-benzhydryl-protected L-α-aminoadipic acid and glycyl-L-α-aminoadipic acid, followed by oxidation with m-chloroperoxybenzoic acid and complete deprotection with formic acid. The conformations of the sulfoxides, and related thiazepines and thiazepine sulfoxides, have been examined by 1Hmr spectroscopy. All thiazepines, and the two title sulfoxides, appear to exist in a twist boat conformation. Most other sulfoxides exist in a chair conformation, which is stabilized by an internal hydrogen bond between the sulfinyl oxygen and the amide proton at C6; when this hydrogen bond is not present, both chair and twist boat conformations may be observable. The title compounds are of interest as possible intermediates in penicillin biosynthesis from glycyl-δ-(L-α-aminoadipyl)-L-cysteinyl-D-valine (GACV) or ACV, according to a new theory, which deals, in particular, with the stereochemical course of the biosynthesis at the beta (β) carbon atom of valine.

Infrared and 1H NMR structural study of 3-tropane, 3-granatane and 3-bicyclo(3.2.1)octane epimeric amino acids

Five amino acids with known configuration: α- and β-3-amino-tropane- and 3-amino-bicyclo(3.2.1)octane-3-carboxylic acids and α -3-amino-granatane-3-carboxylic acid have been studied by i.r. and 1H NMR spectroscopy. Both α- and γ-zwitterion structures have been found for tropane and granatane amino acids. Equatorial and axial ammonium groups in α-zwitterions can be distinguished by the number and frequencies of the ammonium deformation modes. A chair—boat conformation has been deduced for α-3-amino-granatane-3-carboxylic acid.

Stereochemistry of a novel sesquiterpene lactone. X-Ray determination of the structure of ursiniolide a monohydrate

The crystal and molecular structure of ursiniolide A monohydrate has been determined by direct methods from intensity data collected on a diffractometer and refined by full-matrix least-squares to R 0.043 over 1 321 reflections. Crystals are tetragonal, space group P41, with a=b= 13.921(2), c= 11.187(1)A, Z= 4. The cyclodeca-trans,trans-1(10),4-diene ring is in the chair-boat conformation with the two methyl groups at C(4) and C(10) in a syn-α-orientation. The α-methylene-γ-lactone is cis-fused at C(6) and C(7) and adopts a distorted half-chair conformation. The water molecules and the molecules of urisiniolide A form a hydrogen-bonded array running along the 41 axis. The compound investigated is representative of a group of ursiniolides, the only germacranolides described so far with a lactone ring closed at C(6) and cis-annelated to a ten-membered homocycle.

Crystal and molecular structure of an eight-membered cyclic imidosulphite, 2-(2,4,6-trichlorophenylimino)perhydro-1,3,2,6-dioxathiazocine

2-(2,4,6-Trichlorophenylimino)perhydro-1,3,2,6-dioxathiazocine crystallises in the triclinic space group P, with four molecules in a unit cell of dimensions a= 10.725(4), b= 11.730(2), c= 12.451(3)Å, α= 108.15(8), β= 92.92(7), γ= 93.50(7)°. The structure was refined to R 0.048 for 5 024 reflections. Two pseudo-enantiomorphic independent molecules are observed. In the solid state, the molecule assumes an approximate boat-chair conformation with transannular S ⋯ N distances of 2.94 and 2.99 Å. This weak interaction of electrostatic nature is also present in solution. In CDCl3 and C6D6 i.r. and n.m.r. experiments are in agreement with the existence of an enantiomeric equilibrium of two isoenergetic boat-chair forms involving a pseudorotational path.

NOTIZEN. The Conformations of Oxacyclooctanes

Abstract The geometries and energies of the conformers of oxocane, the isomeric di-and trioxocanes, and of 1,3,5,7-tetroxocane were calculated by molecular mechanics. A boat-chair conformation was preferred by all molecules. From the preference of oxygen in the boat-chair conformations of oxocane (position 3 over 1 over 4) the preferred boat-chair form of all other oxocanes can be derived. The results are compared to experi-mental data, which in part can be reinterpreted. Additional CNDO/2 and MINDO/3 calculations were performed for 1,3,5,7-tetroxocane.

Some studies on the solvolysis of 1-chloro-1-alkyl cycloalkanes

The effect of the bulk of the sidechain on the rate of solvolysis of 1-alkyl cyclopentyl, cyclohexyl, and cycloheptyl chlorides has been studied. With the exception of the t-butyl systems, the ratio of solvolysis rates for the three ring systems falls in a given series. The slower rate of solvolysis in the six-membered ring system may be due to an extra activation energy contribution caused by the conversion of a neutral chair form to the twist boat or half chair conformation, prior to the actual solvolysis. In the case of five- and seven-membered ring systems the formation of an intermediate carbonium ion is sterically favoured (I-strain or eclipsing interaction) consistent with earlier findings. The faster rate of solvolysis of 1-t-butylcycloalkyl chlorides is likely due to a rearrangement reaction where alkyl participation enhances the rate of solvolysis.

The Crystal and Molecular Structure of Epoxyisoacoragermacrone

Abstract The crystal and molecular structure of epoxyisoacoragermacrone, which is an important derivative of acoragermacrone isolated from Acorus calamus L. for the study of the structural organic chemistry and biogenetic reactions, has been determined by the X-ray method. The crystal is orthorhombic, P212121, with lattice parameters a=7.425(2), b=26.604(8), and c=7.150(2) Å. The ten-membered ring is in a boat-chair conformation similar to the highly strained cis, trans-germacradiene system. The methyl groups take the axial and syn arrangement, and are on the β-face of the medium ring.

Structure elucidation with lanthanide induced shifts. 9. bicyclo[3.3.1]nonan-9-one

Lanthanide shift reagents have been used for the conformational analysis of bicyclo[3.3.1]-nonan-9-one. Comparison of predicted shifts and experimental values obtained with Eu(fod) 3 indicate that the boat-chair conformation constitutes 22% of the mixture of conformers.

Conformational analysis of 3-borabicyclo[3.3.1]nonane derivatives

Conformations of 3-borabicyclo[3.3.1]nonane derivatives have been studied by means of 1H and 13C NMR spectroscopy. With the aid of the coupling constants 3J(HH) and 13C chemical shifts it has been shown that all the derivatives of 3-borabicyclo[3.3.1]nonane with the trigonal boron atom studied are in a flattened double-chair conformation. In 3-borabicyclo[3.3.1]nonane derivatives with the tetra-coordinated boron atom and substituents at the 7α-position, the chair-boat conformation predominates, the boat conformation being characteristic of the cyclohexane ring; exceptions are the compounds with the internal donor—acceptor bond between the boron atom an 7α-substituent.

Crystal and molecular structure of 1′,2:4,6-di- O-isopropyl-idenesucrose tetra-acetate: a unique example of a d-fructofuranosyl ring in a sucrose derivative puckered at oxygen

Crystals of the title compound are monoclinic, space group P2 1, with cell dimensions: a = 11.260(5), b = 8.841(7), c = 15.605(6) Å, β = 102.25(7)°, and Z = 2; 2888 independent reflections, measured on a diffractometer, have been refined to R = 0.055 in the molecule, the pyranosyl ring has the expected 4 C 1 conformation. However, the conformation of the d-fructofuranosyl ring is unexpected [P = 277.1°] with O-2′ exo to C-6′ furthest from the ring plane. The reason for this conformation, previously unknown in sucrose-related molecules, is not readily apparent from the crystal structure the eight-membered ring, however, has the expected boat-chair conformation.

ChemInform Abstract: STUDIES ON 5‐8 FUSED RING COMPOUNDS. II. THE CRYSTAL AND MOLECULAR STRUCTURE OF 7‐BROMO‐4,4‐DIMETHYLBICYCLO(6.3.0)UNDECANE‐2,6‐DIONE

AbstractDie Titelverbindung kristallisiert triklin in der Raumgruppe Pi mit Z=2.

ChemInform Abstract: MECHANISM OF OLEFIN REARRANGEMENTS INDUCED BY IRON CARBONYLS. REARRANGEMENTS IN THE BICYCLO(6.1.0)NONENE SYSTEM

AbstractDas Bicyclononen‐(4) (I), dargestellt aus Cyclooctadien‐(1,5) und Chloroform in 68proz. Ausb., lagert sich in Gegenwart von Nonacarbonyldieisen zu den Isomeren (II) und (III) um; abhängig von der Reaktionsdauer ist (II) oder (III) (Umlagerungsprodukt von (11)) das Hauptprodukt.