57665-71-1Relevant academic research and scientific papers
Reactivities and products of free radical oxidation of cholestadienols
Xu, Libin,Porter, Ned A.
, p. 5443 - 5450 (2014)
7-Dehydrocholesterol (7-DHC) is the most oxidizable lipid molecule reported to date, with a propagation rate constant for free radical peroxidation that is 200 times that of cholesterol. To better understand the high reactivity of 7-DHC and elucidate the reaction mechanism, we synthesized conjugated and skipped nonconjugated cholestadienols that would give one of the two putative pentadienyl-radical intermediates formed in 7-DHC peroxidation. The additional dienols include 6,8(9)-dienol, 5,8(14)-dienol, 6,8(14)-dienol, and the biologically important 8-dehydrocholesterol (8-DHC; 5,8(9)-dienol). We found that all of the dienols are significantly (at least 40 times) more reactive than cholesterol. Among them, dienols leading to the formation of the pentadienyl radical in ring B (termed endo-B) of the sterol are more reactive than those leading to the pentadienyl radical spanning rings B and C (termed exo-B). By comparing the oxysterol profile formed from 7-DHC and those formed from 8-DHC and 5,8(14)-dienol, products formed from abstraction of the hydrogen atoms at C-9 and C-14 (H-9 or H-14 mechanism) were clearly differentiated. When the oxidation was carried out in the presence of the good hydrogen atom donor α-tocopherol, the oxysterol profile of 7-DHC peroxidation differed distinctly from the profile observed in the absence of the antioxidant and resembles more closely the profile observed in biological systems. This study suggests that oxidative stress and the accumulation of oxysterols should be considered as two key factors in cholesterol biosynthesis or metabolism disorders, where dienyl sterol intermediates are accumulated.
Stereo and chemical course of acid-catalyzed double bond migration of cholesta-5,7-dien-3β-ol to 5α-cholesta-8,14-dien-3β-ol
Seto, Hideharu,Fujioka, Shozo,Koshino, Hiroyuki,Takatsuto, Suguru,Yoshida, Shigeo
, p. 1697 - 1703 (2007/10/03)
Acid-catalyzed double bond migration of steroid 5,7-dienes to the 5α-8,14-dienes, a well-known reaction in steroid chemistry, was reinvestigated by using cholesta-5,7-dien-3β-ol 1, and the stereo and chemical course of this reaction was detailed. Treatment of 1 with 36% hydrochloric acid in refluxing ethanol for 3 h afforded a 6:11:65:16:2 mixture of dienols (93%): 5α- and 5β-cholesta-6,8(14)-dien-3β-ols 7a,b, 5α- and 5β-cholesta-8,14-dien-3β-ols 2a,b, and 5α-cholesta-14,16-dien-3β-ol 10a, along with a mixture of enones (1.7%): 5β-cholest-8(14)-,5β-cholest-14- and 14-epi-5β-cholest-8-en-3-ones 11-13. The experiments using 7a,b and 2a,b suggested the reaction sequence: 1→7a,b?7,14-dienols 8a,b?2a,b?8(14),15-dienols 9a,b?10a,b, in which 8a,b?9a,b should be also implicated. The initial step, 1 to 7a,b proceeded irreversibly with the stereoselectivity, ca. 7:3 of 5α-H to 5β-H. Dienols 7a, 8a, 2a and 10a with 5α-H were identified, which were equilibrated at 6:0:92:2. Among dienols with 5β-H, only 7b and 2b were identified, which were equilibrated at 2:98, and this interconversion proceeded in competition with an intramolecular hydride shift from the C-3α to C-6α of 7b, leading to the formation of a mixture of enones 11-13. The considerable difference in activation energies between 1→7a,b and 7a,b→8a,b/11-13 realized the predominant formation of 7a,b: by treatment at 30°C for 44 h, 1 gave a 53:27:5:15 mixture (94%) of 7a, 7b, 8a and 2a. The Royal Society of Chemistry 2000.
SYNTHESIS OF POTENTIAL ECDYSTEROID PRECURSORS FROM Δ7,22 STEROLS
Hedtmann, Udo,Hobert, Kurt,Milkova, Tsenka,Welzel, Peter
, p. 1941 - 1952 (2007/10/02)
Two routes for the conversion of 5α-cholest-7-ene-3β-ol (11) into 7, which has the typical ecdysteroid substitution pattern in rings B, C, and D, have been developed.Making use of one of the methods, 5,6-dihydroergosterol (31) was converted into the 38, p
