Introduction

Duax, William L.; Norton, D. A.

doi:10.1007/978-1-4684-6150-3_1

Cited by 91 publications

(114 citation statements)

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“…1) is almost planar, maximum deviation from the least squares planes are 0.020(3) Å in 1, 0.006(2) Å in 2 and 0.033(2) Å in 3. Rings B are all close to the sofa conformation; the asymmetry parameters [33] which describe the deviations of these rings from their ideal C s symmetry are 3.3, 5.8 and 3.7°. Finally, the rings C are almost ideal chairs, with the appropriate asymmetry parameters DC s and DC 2 not larger than 5°.…”

Section: Resultsmentioning

confidence: 99%

The Role of Halogen Bonding in Crystal Structures of 3-Halogeno Cytisine Derivatives

Przybył

Kubicki

2012

J Chem Crystallogr

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The crystal structures of three 3-halogeno derivatives of 13N-substituted cytisine have been determined by X-ray diffraction. The two 13-acetyl substituted compounds, 3-bromo (1) and 3-iodo (2) are isostructural, with the isostructurality index as high as 99%. They both crystallize in monoclinic P2 1 space group, with unit cell parameters of a = 8.4709(10) Å , b = 9.2266(12) Å , c = 8.6051(10) Å , b = 98.528 (11)8 (1) and a = 8.2322(6) Å , b = 9.1724(7) Å , c = 8.5494(6) Å , b = 98.181 (7)8 (2). In turn, 3-bromo-13-t-butyl-carbonate derivative (3) crystallizes in orthorhombic P2 1 2 1 2 1 space group with a = 6.8171(3) Å , b = 7.8994(4) Å , c = 31.4657(15) Å . Conformation of the cytisine skeleton is similar in all three molecules, with almost planar A ring, sofa conformation of B-ring and C ring being an almost ideal chair. However, the orientations of the double C=O bonds in 13N-substituents are completely different: in 1 and 2 it is cis with respect to C12 (C12-N13-C14-O15 torsion angle is 3.3(4)8 in 1 and 1.3(6)8 in 2) while in 3 it is trans (-175.4(3)8). In the structures of 1 and 2 the driving force of the crystal architecture are quite strong C-HÁÁÁX halogen bonds with CÁÁÁX distances far shorter than the sums of van der Waals radii (CÁÁÁBr in 1 is 2.9430(19) Å and CÁÁÁI in 2 2.974(3)). In contrast in 3-partially as the consequence of different orientation of the substituent-there are no halogen bondings but instead some weak C-HÁÁÁO contacts organize the molecules into two-dimensional patterns.

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Section: Resultsmentioning

confidence: 99%

The Role of Halogen Bonding in Crystal Structures of 3-Halogeno Cytisine Derivatives

Przybył

Kubicki

2012

J Chem Crystallogr

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“…In both cases of the doubled asymmetric unit content, both molecules posses the same configuration of chiral centres. Six-membered rings possess twelve potential symmetry elements which must be considered in order to determine the solid state conformation of the ring, and this can be done by calculation of two types of asymmetry parameters [81]: 1a, 1b, 2a, 2b) is shown in Fig. 1.…”

Section: Resultsmentioning

confidence: 99%

Conformation of Sterically Hindered 4-Methyl-2-oxo-2-trityl-1,3,2-dioxaphosphorinane in the Solid State and the Solution

Kruszyński

Czubacka

Trzęsowska-Kruszyńska

et al. 2011

J Chem Crystallogr

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The cis-and trans-2-methyl-2-oxo-2-trityl-1,3,2-dioxaphosphorinanes were obtained in the Arbuzov reaction of 2-methoxy-4-methyl-1,3,2-dioxaphosphorinane with trityl chloride. The NMR spectra ( 1 H, 13 C and 31 P) in solution indicated that trans isomer exists in the form of two noncongruent molecules and it adopts two different conformations: a halfchair and a sofa, while the cis isomer exists as the mixed half/chair-sofa conformer. The compounds crystallise as a pure chiral forms and as a racemates. The solid state structural studies show that NMR data are consistent with the single crystal X-ray analysis, but the conformation existing in the crystal structure is more complex than it can be supposed on sole NMR determination. Crystal data: cis-isomer chiral form: space group P3 2 , a = 8.

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“…Molecular modelling studies performed on the IBM PC/AT using the ALCHEMYII program (Tripos Associates, 1988). Table 2 shows the bond lengths, bond angles and torsion angles of the non-H atoms, which are within the range of expected values (Duax & Norton, 1975;Griffin, Duax & Weeks, 1984 (2) 4.95 (6) C17 0.40967 (7) 0.5587 (5) C4---C5 and C6---C7 bonds. C9 is below the C5--C6--C7--C8 plane (-0.504 A) and C10 is above by 0.201 A.…”

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confidence: 96%

“…2). Of the ten pregnanes containing a 21-acetate moiety tabulated in the Atlas of Steroid Structure (Duax & Norton, 1975;Griffin et al, 1984), nine have a C20--C21--O22--C23 torsion angle in the range -70.8 to -106.2 ° (average -84.2__ 13.7°). Only 4a,6,7a-trichloro-3,11,20-trioxo-5-pregnene-17,21-diol 21-acetate has a positive C20--C21--O22--C23 torsion angle (95.0 °) (Kierstead, Blount, Fahrenholtz, Faraone, LeMahieu & Rosen, 1970;Griffin et al, 1984).…”

mentioning

confidence: 99%

Structure of cortivazol, 11β,17α,21-trihydroxy-6,16α-dimethyl-2'-phenyl-2'H-pregna-2,4,6-trieno[3,2-c]pyrazol-20-one 21-acetate

Czerwinski¹

1991

Acta Crystallogr C

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Introduction

Cited by 91 publications

References 0 publications

The Role of Halogen Bonding in Crystal Structures of 3-Halogeno Cytisine Derivatives

The Role of Halogen Bonding in Crystal Structures of 3-Halogeno Cytisine Derivatives

Conformation of Sterically Hindered 4-Methyl-2-oxo-2-trityl-1,3,2-dioxaphosphorinane in the Solid State and the Solution

Structure of cortivazol, 11β,17α,21-trihydroxy-6,16α-dimethyl-2'-phenyl-2'H-pregna-2,4,6-trieno[3,2-c]pyrazol-20-one 21-acetate

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