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.

(3aS,5aR,6R,8aR)-3a-Hydroxy-5a-methyl-6-[(1R,2E,4R)-1,4,5-trimethyl-2-hexen-1-yl]-3a,4,5,5a,6,7,8,8a-octahydro-2H-cyclopenta[e]benzofuran-2-one

2007 ◽  
Vol 63 (11) ◽  
pp. o4196-o4196
Author(s):  
Wen-liang Wang ◽  
Hong-wen Tao ◽  
Wei Sun ◽  
Qian-Qun Gu ◽  
Wei-Ming Zhu
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Absolute Configuration ◽  
Title Compound ◽  
Optical Rotation ◽  
Side Chain ◽  
Compound C ◽  
Extended Chain ◽  
Halotolerant Fungus ◽  
The Absolute

The title compound, C21H32O3, also known as dimethylincisterol A3, was isolated from halotolerant fungus THW-18. It is composed of three fused rings and a side chain. In the crystal structure, the molecules interact with each other via O—H...O hydrogen bonds, resulting in an extended chain along the b axis. The absolute configuration was assigned from the measured optical rotation and reference to the literature.

scholarly journals Circular Dichroic Properties of Flavan-3-ols

1999 ◽  
Vol 23 (7) ◽  
pp. 450-451
Author(s):  
Hendrik van Rensburg ◽  
Petrus J. Steynberg ◽  
Johann F. W. Burger ◽  
Pieter S. van Heerden ◽  
Daneel Ferreira
Keyword(s):  
Absolute Configuration ◽  
Heterocyclic Ring ◽  
The Absolute ◽  
Derivatives Of ◽  
Circular Dichroic

CD data of all four diastereoisomers of the permethylaryl ether 3- O-acetyl derivatives of a series of flavan-3-ols permit assignment of the absolute configuration at the stereocentres of the heterocyclic ring.

X-ray crystal structure analysis of a bisepoxide derived from secologanin: the structure and absolute configuration

1983 ◽  
Vol 61 (2) ◽  
pp. 282-283 ◽  
Author(s):  
Stanley C. Nyburg ◽  
Pik Y. Siew ◽  
Gavin N. Saunders ◽  
John R. Purdy ◽  
Stewart McLean
Keyword(s):  
Crystal Structure ◽  
Structure Analysis ◽  
Absolute Configuration ◽  
Dimethyl Acetal ◽  
Crystal Structure Analysis ◽  
Side Chain ◽  
Bench Mark ◽  
Chemical Transformations ◽  
X Ray ◽  
Derivatives Of

The structure and absolute configuration of a bisepoxide (2) produced by oxidation of tetraacetylsecologanin dimethyl acetal (1) with m-chloroperbenzoic acid have been established by X-ray crystal structure analysis. Epoxidation of the vinyl side chain is unexceptional; epoxidation of the β-alkoxyacrylate moiety is novel. This determination represents a valuable bench mark for configurational assignments, since the bisepoxide has been correlated by chemical transformations with a number of synthetic and naturally-occurring derivatives of secologanin.

Pterins. VIII. The absolute configuration at C 6 of natural 2-Amino-6-[(1'R,2'S)- 1',2'-dihydroxypropyl]-5,6,7,8-tetrahydropteridin-4(3H)-one (L-erythro-5,6,7,8-tetrahydrobiopterin)

1982 ◽  
Vol 35 (4) ◽  
pp. 785 ◽  
Author(s):  
WLF Armarego ◽  
P Waring ◽  
B Paal
Keyword(s):  
Hydrochloric Acid ◽  
Absolute Configuration ◽  
Side Chain ◽  
Methyl Group ◽  
Convenient Synthesis ◽  
The Absolute

The conformation of the side chain of 5,6,7,8-tetrahydrobiopterint (6) in 0.5 M DCl/D2O is predominantly quasi-equatorial (deduced from 3J (13C4a, 1H6) 1.1 HZ), and is the same as that of the methyl group in 2-methyl-1,2,3,4-tetrahydroquinoxaline and in 2-amino-6-methyl-5,6,7,8-tetrahydropteridin-4(3H)-one in the same solvent. Because (-)-(2S)-2-methyl-1,2,3,4-tetrahydroquinoxaline(4) and (-)-(6S)-2-amino-6-methyl-5,6,7,8-tetrahydropteridin-4(3H)-one (5) have the same conformation and negative c.d. spectra (O 248 nm and 263 nm respectively) as does the natural 5,6,7,8, tetrahydrobiopterin (O minimum at 265 nm) in 0.1 M hydrochloric acid, then the absolute conformations of the tetrahydropyrazine rings and the absolute configurations at the chiral centres C2, C6, and C6 of compounds (4), (5) and (6) respectively are the same. Hence the absolute configuration at C6 in natural 5,6,7,8 tetrahydrobiopterin is R.� A convenient synthesis of biopterin on a gram scale is described.

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.

Sign in / Sign up

Export Citation Format

Share Document