Preparation and absolute configuration at C(20) of 21-nor-5α-chol-22-en-24→20-olide derivatives

1981 ◽  
Vol 46 (4) ◽  
pp. 917-925 ◽  
Author(s):  
Vladimír Pouzar ◽  
Miroslav Havel
Keyword(s):  
Absolute Configuration ◽  
Nmr Spectra ◽  
Lithium Salt ◽  
H Nmr ◽  
Chemical Correlation ◽  
Unsaturated Lactones

Reaction of the aldehyde I with the lithium salt of 1-(2-tetrahydropyranyloxy)-2-propyne yielded the compounds II and IV. From the compound II the lactone XII was prepared via the intermediates III and X, the lactone XVIII was prepared from the substance IV via the intermediates V and XVI. The unsaturated lactones XII and XVIII were also prepared by sulfenylation and dehydrosulfenylation of the saturated lactones XIII and XIX. Based on chemical correlation and 1H-NMR spectra analyses of the compounds II and IV, the lactone XII was assigned the 20R-configuration whereas the lactone XVIII was allotted the 20S-configuration.

Preparation of 21,26,27-trinor-5α-cholest-23-en-25→20-olide from a propargyl synthone

1984 ◽  
Vol 49 (4) ◽  
pp. 871-880 ◽  
Author(s):  
Vladimír Pouzar ◽  
Pavel Drašar ◽  
Ivan Černý ◽  
Miroslav Havel
Keyword(s):  
Carbon Atom ◽  
Absolute Configuration ◽  
Lithium Salt ◽  
Side Chain ◽  
Alternative Synthesis ◽  
Chemical Correlation ◽  
Unsaturated Lactones

Reaction of 21-nor-5α-pregnan-20-al (I) with propargylmagnesium bromide afforded two isomeric 21-nor-5α-chol-23-yn-20-ols (II and IV) whose absolute configuration at C(20) was determined by chemical correlation with the known 21-nor-5α-cholan-20-ols (VI and VII). Extension of the side-chain in the compound by one carbon atom gave (20R)-21,26,27-trinor-5α-cholest-23-yne-20,25-diol (XIV). The isomeric (20S)-diol XX was obtained by the same procedure from the alcohol IV. Alternative synthesis of the diols XIV and XX by reaction of the lithium salt of 1-methoxymethoxy-2-propyne with (20S)-20,21-epoxy-5α-pregnane (XV) and the (20R)-isomer XXI, respectively, gave only low yields. The diols XIV and XX were converted into the respective unsaturated lactones, i.e. (20R)-21,26,27-trinor-5α-cholest-23-en-25→20-olide (XVII) and (20S)-21,26,27-trinor-5α-cholest-23-en-25→20-olide (XXIII).

Preparation and absolute configuration at C(20) of 21-nor-5α-cholan-24→20-olide derivatives

1981 ◽  
Vol 46 (1) ◽  
pp. 107-117 ◽  
Author(s):  
Vladimír Pouzar ◽  
Miroslav Havel
Keyword(s):  
Acetic Acid ◽  
Absolute Configuration ◽  
Nmr Spectra ◽  
Lithium Salt ◽  
Diethyl Malonate ◽  
Methyl Propionate ◽  
H Nmr ◽  
Sodium Diethyl Malonate

The lactones X and XI were obtained on reaction of the aldehyde III with lithium salt of methyl propionate followed by hydrogenation of the intermediary esters IV and V. Treatment of the epoxides XXI and XXII with dilithium salt of acetic acid yielded the lactones X and XI. These lactones were also obtained by reaction of the epoxides XXI and XXII with sodium diethyl malonate through intermediates XXIII and XXV. The preparation of α-methylene lactones XXVII and XXVIII is also described. The 20R configuration was established for the lactones X, XXIII and XXVII while the lactones XI, XXV and XXVIII were assigned the 20S configuration both on the basis of 1H-NMR spectra and chemical correlations.

Preparation and absolute configuration at C(22) of 21,26,27-trinor-5α-cholestane-22,25-diol derivatives

1983 ◽  
Vol 48 (8) ◽  
pp. 2423-2435 ◽  
Author(s):  
Vladimír Pouzar ◽  
Soňa Vašíčková ◽  
Pavel Drašar ◽  
Ivan Černý ◽  
Miroslav Havel
Keyword(s):  
Absolute Configuration ◽  
Lithium Salt ◽  
Nickel Acetylacetonate ◽  
Cotton Effects ◽  
Chemical Correlation

Reaction of 5α-pregnan-21-al (V), obtained from ester of the corresponding acid III via the alcohol IV, with lithium salt of 1-methoxymethoxy-2-propyne afforded both the isomeric 25-methoxymethoxy-21,26,27-trinor-5α-cholest-23-yn-22-ols (VI and VIII) which were converted into two 21,26,27-trinor-5α-cholestane-22,25-diols (XI, XV). Absolute configuration of the alcohols X and XIV was assigned by chemical correlation with derivatives XXVI and XXVII of known absolute configuration at C(20). The correlation was based on reduction of thiocarbonates derived from the diols XXII and XXIV for which also Cotton effects of their complexes with nickel acetylacetonate were studied. Both diols were prepared from 5α-pregnan-20-one (XVIII) via 5α-pregn-20-yne (XIX) and the 21,26,27-trinor-5α-cholest-20-ene derivative XXI.

Structure of isosilerolide, relative and absolute configuration of silerolide and lasolide - Sesquiterpenic lactones of new stereoisomeric type of eudesmanolides

1986 ◽  
Vol 51 (4) ◽  
pp. 903-929 ◽  
Author(s):  
Miroslav Holub ◽  
Miloš Buděšínský ◽  
Zdenka Smítalová ◽  
David Šaman ◽  
Urszula Rychłewska
Keyword(s):  
Absolute Configuration ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Nmr Data ◽  
Chemical Correlation ◽  
The Absolute

On the basis of spectroscopic, particularly 1H NMR data, isosilerolide was assigned structure I, including the absolute configuration. The structure was confirmed by X-ray diffraction. Isosilerolide represents a new stereoisomeric type of natural eudesmanolides, characterized as 5βH, 6αH, 7αH, 10αCH3-eudesman-6,12-olide. As shown by the chemical correlation of isosilerolide (I) with silerolide (III) and lasolide (X), the latter two natural lactones belong to this stereoisomeric group of eudesmanolides. Analysis of models and 1H NMR data shows that structures of some eudesman-6,12-olides, published by other authors, should be corrected.

1H—NMR-spektroskopische Bestimmung der diastereomeren Reinheit und der absoluten Konfiguration am Phosphoratom von tButyl-phenyl-phosphinsäure-(—)-menthylester / Determination of the Diastereomeric Purity and the Absolute Configuration at Phosphorus of tButyl-phenyl-phosphinic Acid (—)-Menthyl Ester by Means of 1H NMR Spectroscopy

1977 ◽  
Vol 32 (5) ◽  
pp. 589-593 ◽  
Author(s):  
Reiner Luckenbach ◽  
Hans-H. Bechtolsheimer
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
Absolute Configuration ◽  
1H Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Phosphinic Acid ◽  
H Nmr ◽  
The Absolute ◽  
Diastereomeric Purity

The preparation and separation into diastereomers of tbutyl-phenyl-phosphinic acid (—)-menthyl ester (1a) is reported. The diastereomeric purity as well as the absolute configuration at phosphorus of 1 a can be deduced from the detailed analysis of the 1H NMR spectra of samples of 1a differing in their diastereomer ratios.

scholarly journals Determination of Absolute Stereochemistry of Natural Alicyclic Glycosides by 1H NMR Spectroscopy without Application of Chiral Reagents – An Indication

2011 ◽  
Vol 6 (5) ◽  
pp. 1934578X1100600 ◽  
Author(s):  
Tatyana N. Makarieva ◽  
Larisa K. Shubina ◽  
Alla G. Guzii ◽  
Natalya V. Ivanchina ◽  
Vladimir A. Denisenko ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
Absolute Configuration ◽  
1H Nmr Spectroscopy ◽  
Nmr Spectra ◽  
H Nmr ◽  
Steroid Glycosides ◽  
The Absolute ◽  
Absolute Stereochemistry

A study has been made of the 1H NMR spectra of peracetylated β-glucopyranosides and α-arabinopyranosides obtained by reaction of D- and L-glucoses, and L- and D-arabinoses with either ( R)- or ( S)-2-octanols. The obtained and literature data show that 1H NMR spectra may be used to determine the absolute configuration of the aglycone moieties of some alicyclic glycosides without the need to synthesize derivatives with chiral reagents, as long as the absolute configuration of their monosaccharide moiety is known or vice versa. Spectra of marine steroid glycosides and their acetates containing glycosylated side chains as alicyclic fragments were also examined. It was shown that analysis of 1H NMR spectra for the determination of the absolute configuration is more applicable in the cases when glycosides have the same substitution in the D-ring of the aglycone moiety.

Notizen: The Absolute Configuration of Julifloridine

1983 ◽  
Vol 38 (5) ◽  
pp. 660 ◽  
Author(s):  
Viqar Uddin Ahmad ◽  
Sabiha Qazi
Keyword(s):  
Absolute Configuration ◽  
Nmr Spectra ◽  
H Nmr ◽  
The Absolute

Abstract The absolute configuration of julifloridine is proposed to be 2 R, 3 R, 6 R through 13C Spectra, 1H NMR Spectra,

Synthesis and absolute configuration at C(20) of 21,26,27-trinor-5α-cholestan-25→20-olide derivatives

1981 ◽  
Vol 46 (11) ◽  
pp. 2758-2765 ◽  
Author(s):  
Vladimír Pouzar ◽  
Miroslav Havel
Keyword(s):  
Absolute Configuration ◽  
Chemical Correlation ◽  
Unsaturated Lactones

Reaction of the aldehyde I with 4-(methoxymethoxy)butylmagnesium chloride yielded compounds II and VII which were converted into diols III and VIII, respectively. By oxidation of the diols III and VIII were obtained saturated lactones XVI and XX, respectively, which were converted into unsaturated lactones XIX and XXIII, respectively. On the basis of chemical correlation with methyl ethers XIV and XV of a known configuration at C(20), the compounds II-VI, XII, XVI-XIX were assigned the 20R-configuration whereas 20S configuration was established for the compounds VII-XI, XIII and XX-XXIII.

Optically active tricyclic dilactams with non-planar cis-amide groups: Synthesis, X-ray, NMR and CD studies

1982 ◽  
Vol 47 (3) ◽  
pp. 1000-1019 ◽  
Author(s):  
Karel Bláha ◽  
Miloš Buděšínský ◽  
Zdena Koblicová ◽  
Petr Maloň ◽  
Miloš Tichý ◽  
...  
Keyword(s):  
Absolute Configuration ◽  
Nmr Spectra ◽  
Condensation Reaction ◽  
Spatial Arrangement ◽  
Coupling Constants ◽  
X Ray Diffraction ◽  
Chiroptical Properties ◽  
X Ray ◽  
H Nmr ◽  
Cd Studies

Three tricyclic dilactams were investigated as models for study of chiroptical properties of homoconjugated non-planar cis-amide groups. Racemic 5,8-diazatricyclo[6,3,0,01,5]undecane-4,9-dione (I) was partially resolved into enantiomers by chromatography on acetylcellulose. The 6-isobutyl (II) and 6-methyl (III) derivatives were prepared in optically pure forms by condensation of diethyl 4-oxoheptanedioate with (S)-1,2-diamino-4-methylpentane and (S)-1,2-diamino-propane, respectively. The respective diamines were synthesized starting from (S)-leucine and (S)-alanine: this determined the absolute configuration on the C(6) atom in both dilactams. As shown by 1H and 13C NMR spectra, the condensation reaction afforded only one of the two possible diastereoisomeric dilactams. The configurational relation between the chiral center at C(6) and the chirality of the tricyclic moiety was derived from coupling constants in the 1H NMR spectra. The configuration of compound II was confirmed by X-ray diffraction. According to 1H NMR spectra, the spatial arrangement of II in solution is similar to that in crystal, the only difference being in the local conformation of the isobutyl side chain at C(6). IR spectroscopy identified only minor differences in geometry of the two lactam groupings in II and III. All CD parameters of compounds I-III, measured in various solvents, are very similar. The CD curves show the same absolute configuration (1S, 6S) of compounds II and III and the opposite configuration of the studied enantiomer of I(1R). Parameters of the n-π dichroic band indicate a non-planar amide-grouping whose geometry is known from the X-ray analysis. Its sign agrees with the relationship derived for the chiroptical properties of defined pyramidicity on nitrogen atom in non-planar amides. The π-π dichroic bands exhibit an exciton splitting into a couplet as a result of interaction between the amide groups.

Constituents of frontal gland secretion of peruvian termites Nasutitermes ephratae

1986 ◽  
Vol 51 (12) ◽  
pp. 2884-2895 ◽  
Author(s):  
Irena Valterová ◽  
Soňa Vašíčková ◽  
Miloš Buděšínský ◽  
Jan Vrkoč
Keyword(s):  
Absolute Configuration ◽  
Nmr Spectra ◽  
Phenylacetic Acid ◽  
Volatile Fraction ◽  
Cd Spectra ◽  
Model Compounds ◽  
Frontal Gland ◽  
Defense Secretion ◽  
H Nmr ◽  
Work Up

The defense secretion of Nasutitermes ephratae soldiers was analyzed and its constituents were identified. The volatile fraction contains monoterpenic hydrocarbons α-pinene, camphene, sabinene, β-pinene, myrcene, 4-carene, 3-carene, α-terpinene, limonene, γ-terpinene, β-phellandrene, and terpinolene. From the non-volatile fraction four alcohols derived from trinervitane skeleton were isolated: 1(15),8(19)-trinervitadien-3α-ol (I), 1(15),8(19)-trinervitadien-2β,3α-diol (II) and its 2α,3α- (III) and 2α,3β- (IV) isomers. 3α-Hydroxy-1(15),8(19)-trinervitadien-2-one (V), which was also isolated, is probably an artefact formed during the work-up of the extract. The structure of 3β-hydroxy-1(15),8(19)-trinervitadien-2-one (VI) was determined on the basis of mass, IR and 1H NMR spectra, comparison with model compounds and analogy with the literature. The absolute configuration of the trinervitane skeleton was studied by CD spectra of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)praseodymium complexes of the 2,3-diols II-IV and by the 1H NMR spectra of esters of the alcohol I with (R)- and (S)-α-methoxy-α-(trifluoromethyl)phenylacetic acid. The results obtained by both methods are identical and confirm the earlier suggested absolute configuration of the trinervitane skeleton.

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