Acid catalysed backbone rearrangement of cholesta-2,4,6-triene: On the origin of ring A and ring B aromatic steroids in recent sediments
نویسندگان
چکیده
Rearrangement of cholesta-2,4,6-triene in the presence of p-toluenesulfonic acid in acetic acid at 70 C leads to 4-methyl-19-nor-cholesta-1,3,5(10)-triene and 1(10 ! 6)-abeo-14b-cholesta-5,7,9(10)-triene in less than 2 h. Postulated mechanisms of formation of these products are supported by molecular mechanics calculations of the relative stabilities of reaction intermediates. The results suggest that D-sterols, the most common natural precursors of triunsaturated steroidal hydrocarbons in contemporary sediments, constitute another major source for monoaromatic A and B steroids in addition to D-sterols. 2006 Elsevier Ltd. All rights reserved.
منابع مشابه
The synthesis of Beta-Carbonhomologous Intermediate of Norcardicin A. A General Method for Selective Preparation of The Beta-Lactam Ring in the Presence of Free Phenolic Hydroxyl Groups
The synthesis of cis-N-[a-carbobenzyloxy-b-(p-hydroxyphenyl)ethyl]-3-phthalimido-4-styryl-2-azetidinone is described. We have found that the electron-rich Schiff bases can afford the cis-b-lactam ring even in the presence of the free hydroxyl functions. The mechanisms of cis and trans-b-lactam ring formation are discuss...
متن کاملQuinolones: Recent Structural and Clinical Developments
Quinolones are a very important family of antibacterial agents that are widely prescribed for the treatment of infections in humans. Since their discovery in the early 1960s, the quinolone group of antibacterials has generated considerable clinical and scientific interest. Two major groups of compounds have been developed from the basic molecule: quinolones and naphthyridones. The 4-pyridone-3-...
متن کاملQuinolones: Recent Structural and Clinical Developments
Quinolones are a very important family of antibacterial agents that are widely prescribed for the treatment of infections in humans. Since their discovery in the early 1960s, the quinolone group of antibacterials has generated considerable clinical and scientific interest. Two major groups of compounds have been developed from the basic molecule: quinolones and naphthyridones. The 4-pyridone-3-...
متن کاملRelative stabilities of cholestadienes calculated by molecular mechanics and semi-empirical methods: application to the acid-catalyzed rearrangement reactions of cholesta-3,5-diene
The study of geochemical transformations undergone by `biological markers' after their incorporation into sediments is an important ®eld of organic geochemistry. Combined with laboratory simulation experiments, molecular mechanics calculations have been shown to be very useful to establish the reaction pathways, and to predict intermediate components and stable reaction end products, especially...
متن کاملAN APPROACH TO THE A RING OF VITAMIN D ANALOGUES VIA SEQUENTIAL CARBOMETALATION/ ANION CAPTURE
An intramolecular palladium catalysed carbometalation followed by anion capture achieves construction of a model comprised of the A ring of Vitamin D oxygen analogues.
متن کامل