4,5-Seco-4,6-cyclosteroids. II. Synthesis of 4,5-Seco-4,6-cyclo-6β-cholestan-5α-ol

1969 ◽  
Vol 22 (3) ◽  
pp. 627
Author(s):  
DJ Collins ◽  
JJ Hobbs ◽  
RJ Rawson

5-oxo-4,5-secocholestan-4-oic acid methyl ester (XIIIb) was converted into the corresponding cyclic ethylene acetal (XIVb) which, upon successive reduction with lithium aluminium hydride and acid hydrolysis, gave 4-hydroxy-4,5-secochol-estan-5-one (XVa), converted into the tosyl ester (XVb). Base-catalysed intra-molecular alkylation of the latter gave mainly A-homo-4a-oxacholest-5-ene (XVII), together with 4,5-seco-4,6-cyclo-6β-cholestan-5-one (IIIc), reduced with lithium aluminium hydride to 4,5-seco--1,6-cyclo-6β-cholestan-5α-ol (IIb). This was identical with material previously prepared by transformation of 4,5-seco-4,6-cyclo-6β-cholestane-3β,5α-diol (IIa), obtained from reductive rearrangement of 6β-bromo-4β,5-epoxy-5,β-cholestan-3β-ol (I). ��� Some other approaches to the synthesis of 4,5-seco-4,6-cyolo-6β- cholestane derivatives are described.

1999 ◽  
Vol 82 (3) ◽  
pp. 766-769 ◽  
Author(s):  
Fred J Eller

Abstract Gas chromatographic fatty acid methyl ester (GC FAME) analyses of some acid-hydrolyzed foods revealed a large peak that did not correspond to any FAME standards. The unknown peak eluted just after the C12 FAME. If the fatty acid response factor and the conversion factor for the nearest calibrated peak (C12 FAME) were used to determine the total fat, the resulting total fat determination was much higher than expected. This peak was present only in acid-hydrolyzed samples and was absent in extracts obtained with supercritical CO2 or solvents without acid hydrolysis. The compound was isolated, analyzed by mass spectrometry and nuclear magnetic resonance spectroscopy, and proved by synthesis to be methyl-4-oxopentanoate (methyl levulinate). Its source was determined to be sugar in the product formula. Levulinic acid is produced by acid hydrolysis of sugar and is transesterified by BF3 in methanolto methyl levulinate. Although methyl levulinate may appear in the GC analyses of any acid-hydrolyzed products containing sugar, if the ratio of fat to sugar is high, the impact of methyl levulinate on fat determination would be small. Onthe other hand, the presence of methyl levulinate in analyses of low-fat, high-sugar prod ucts is potentially problematic if not recognized, al though GC analysis can account for the presence of this compound.


1959 ◽  
Vol 37 (2) ◽  
pp. 345-350 ◽  
Author(s):  
Arthur A. Amos ◽  
P. Ziegler

Bromination of 3α,12α-diacetoxypregnan-20-one ethylene ketal provided in good yield the corresponding 21-monobromo compound. This product, on acid hydrolysis and subsequent acetolysis, gave the known 3α,12α,21-triacetoxypregnan-20-one. Acid hydrolysis of the bromoketal, followed by Faworsky rearrangement, led to 3α,12α-diacetoxy-17α-methyletiocholanic acid methyl ester.


2013 ◽  
Author(s):  
Jr Morris ◽  
Shardo Robert W. ◽  
Higgins James ◽  
Cook Kim ◽  
Tanner Rhonda ◽  
...  

2020 ◽  
Vol 16 (4) ◽  
pp. 556-567
Author(s):  
Asma Khalil ◽  
Zubair Ahmad ◽  
Farid Touati ◽  
Mohamed Masmoudi

Background: The photo-absorption and light trapping through the different layers of the organic solar cell structures are a growing concern now-a-days as it affects dramatically the overall efficiency of the cells. In fact, selecting the right material combination is a key factor in increasing the efficiency in the layers. In addition to good absorption properties, insertion of nanostructures has been proved in recent researches to affect significantly the light trapping inside the organic solar cell. All these factors are determined to expand the absorption spectrum and tailor it to a wider spectrum. Objective: The purpose of this investigation is to explore the consequence of the incorporation of the Ag nanostructures, with different sizes and structures, on the photo absorption of the organic BHJ thin films. Methods: Through a three-dimensional Maxwell solver software, Lumerical FDTD, a simulation and comparison of the optical absorption of the three famous organic materials blends poly(3- hexylthiophene): phenyl C71 butyric acid methyl ester (P3HT:PCBM), poly[N-9″-heptadecanyl-2,7- carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]: phenyl C71 butyric acid methyl ester (PCDTBT:PCBM) and poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt- 4,7-(2,1,3-benzothiadiazole)]: phenyl C71 butyric acid methyl ester (PCDPDTBT:PCBM) has been conducted. Furthermore, FDTD simulation study of the incorporation of nanoparticles structures with different sizes, in different locations and concentrations through a bulk heterojunction organic solar cell structure has also been performed. Results: It has been demonstrated that embedding nanostructures in different locations of the cell, specifically in the active layer and the hole transporting layer had a considerable effect of widening the absorption spectrum and increasing the short circuit current. The effect of incorporation the nanostructures in the active layer has been proved to be greater than in the HTL. Furthermore, the comparison results showed that, PCDTBT:PCBM is no more advantageous over P3HT:PCBM and PCPDTBT:PCBM, and P3HT:PCBM took the lead and showed better performance in terms of absorption spectrum and short circuit current value. Conclusion: This work revealed the significant effect of size, location and concentration of the Ag nanostructures while incorporated in the organic solar cell. In fact, embedding nanostructures in the solar cell widen the absorption spectrum and increases the short circuit current, this result has been proven to be significant only when the nanostructures are inserted in the active layer following specific dimensions and structures.


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