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.

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).

Absolute configuration at C(20) of the derivatives of 21-nor-5α-cholane-20,24-diol

1980 ◽  
Vol 45 (9) ◽  
pp. 2443-2451
Author(s):  
Vladimír Pouzar ◽  
Miroslav Havel
Keyword(s):  
Absolute Configuration ◽  
Side Chain ◽  
Chemical Correlation ◽  
The Absolute ◽  
Derivatives Of

Derivatives of 21-nor-5α-cholane-20,24-diol XI and XIX were prepared by stepwise construction of the side-chain in the position 17β. Their absolute configuration at C(20) was determined on the basis of chemical correlation with the derivatives of 21-nor-5α-cholan-20-ol, XVI and XXIV. The absolute configuration of alcohols XVI and XXIV was determined from the ratio of the yields in which they are formed during the reduction of ketone X and using the benzoate rule. To compounds XI-XVIII the configuration 20R and to compounds XIX-XXVI the configuration 20S has been assigned.

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.

Chiroptical properties of pyrrolidine derivatives

1983 ◽  
Vol 48 (6) ◽  
pp. 1618-1623
Author(s):  
Otakar Červinka ◽  
Ilja Sedlák ◽  
František Strejček
Keyword(s):  
Wave Function ◽  
Absolute Configuration ◽  
Molecular Geometry ◽  
Cd Spectra ◽  
Chiroptical Properties ◽  
Total Gradient ◽  
Gradient Optimization ◽  
Chemical Correlation ◽  
Rotational Strengths

CD spectra of (S)-(-)-2-phenyl-1-methylpyrrolidine (I) and (S)-(-)-1-methyl-2-(2-tolyl)pyrrolidine (II) were calculated. Rotational strengths were calculated by direct procedure based on the CNDO/S-CI wave function. The most stable conformations were determined by total gradient optimization of molecular geometry and their molar fractions were calculated. CD spectra, constructed from the molar fractions and rotational strengths, agreed well with the experimental ones. Absolute configuration of compound II was established by the chemical correlation with (S)-(-)-hygrinic acid.

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.

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