69422-80-6Relevant articles and documents
Synthesis of [3-D3]-, [3-13C]-, and [1,2-13C2]propynes and their use for the synthesis of [5-D3-methyl]-, [5-13C-methyl]-, and [5,6- 13,C2-2,5-cyclohexadienyl]ubiquinones 3
Boullais, Claude,Rannou, Christelle,Reveillere, Emmanuel,Mioskowski, Charles
, p. 723 - 727 (2007/10/03)
Three selectively labeled propynes were prepared either with deuterium or carbon-13 at position 3 and doubly labeled with carbon-13 at positions 1 and 2 by an alkylation reaction from the corresponding labeled or unlabeled monolithio acetylides and dimethylsulfates. Their lithiation with nBuLi gave the corresponding propynyllithium derivatives which reacted with dimethyl squarate to afford the corresponding propargylic alcohols. These were thermolysed in p-xylene to furnish [5-D3-methyl]-, [5-13C-methyl]-, and [5,6-13C2-2,5-cyclohexadienyl]ubiquinone. The farnesyl side chain was introduced onto the labeled quinones with farnesyl trimethyltin under BF3 catalysis to provide [5-D3-methyl]-, [5-13C-methyl]-, and [5,6-13C2- 2,5-cyclohexadienyl]ubiquinone 3 (6c, 6b, 6a, respectively).
The surprisingly high reactivity of phenoxyl radicals
Foti,Ingold,Lusztyk
, p. 9440 - 9447 (2007/10/02)
Rate constants have been measured in nonaqueous media for hydrogen atom abstraction by the phenoxyl radical from some biologically important phenols and related compounds. Although the thermochemistry for these reactions must be very similar to the thermochemistry for H atom abstraction from the same substrate by a peroxyl radical, the phenoxyl rate constants, k5, are ca. 100-300 times greater than the (already well-known) peroxyl rate constants, k1. For example, with α-tocopherol in benzene/di-tert-butyl peroxide (1:3, v/v) k5293K = 1.1 × 109 M-1 s-1 vs k1303K = 3.2 × 106 M-1 s-1 in a similar nonpolar medium, and with ubiquinol-10 in the same solvent mixture k5293k = 8.4 × 107 M-1 s-1, while the corresponding value for k1 is 3.5 × 105 M-1 s-1. The greater reactivity of the phenoxyl radical has been traced to the fact that the Arrhenius preexponential factors are much larger than for the corresponding peroxyl radical reactions, i.e., A5 ～ 102A1. For example, with α-naphthol log(A5/M-1 s-1) = 8.9 and E5 = 2.2 kcal/mol vs log(A1/M-1 s-1) = 6.4 and E1 = 1.7 kcal/mol. The preexponential factors for H-atom donors more reactive than α-naphthol are even greater; for example, with α-tocopherol in CH3CN/di-tert-butyl peroxide (1:2, v/v) log(A5/M-1 s-1) = 10.0 and E5 = 2.0 kcal/mol, and with ubiquinol-0 in benzene/di-tert-butyl peroxide (1:3, v/v) log(A5/M-1 s-1) = 10.5 and E5 = 3.5 kcal/mol. The role that intermediate hydrogen-bonded complexes between the reacting radical and the phenolic hydrogen donor may play in these reactions is discussed, and it is pointed out that our results are likely to be relevant to in vivo radical chemistry.
Quinones. Part 2. General Synthetic Routes to Quinone Derivatives with Modified Polyprenyl Side Chains and the Inhibitory Effects of these Quinones on the Generation of the Slow Reacting Substance of Anaphylaxis (SRS-A)
Terao, Shinji,Shiraishi, Mitsuru,Kato, Kaneyoshi,Ohkawa, Shigenori,Ashida, Yasuko,Maki, Yoshitaka
, p. 2909 - 2920 (2007/10/02)
General synthetic routes to quinone acids (8), quinone amides (9), quinone alcohols (10), and quinone methylketones (11) with polyprenyl side chains, in which allylic alcohols (3) are employed as the key intermediates, are described.The Claisen rearrangements and the Carrol reactions of the allylic alcohols (3) with ethyl orthoacetate and diketen produced the ethyl esters (4) and the methylketones (5), respectively.Quinone products (8), (10), and (11) were recovered by oxidative demethylation of hydroquinone dimethyl ethers (4), (5), and (7) or by acid hydrolysis of hydroquinone bis(methoxymethyl) ethers (4) and (5) followed by ferric chloride oxidation.Amidation of quinone acids (8) led to the formation of quinone amides (9).Inhibitory effects of these quinone derivatives on the generation of the slow reacting substance of anaphylaxis (SRS-A) in the lungs of sensitised guinea pigs are evaluated.
