56519-61-0Relevant academic research and scientific papers
Hydrolysis of the Vinyl Ether Functional Group in a Model for Prostacyclin in Which the Carboxyl Group Has Been Replaced by a Pyridine Ring
Bergman, Niels-Ake,Halvarsson, Tornbioern
, p. 2137 - 2142 (1989)
The hydrolysis of the vinyl ether functional group in the three isomeric compounds (Z,E)-2-methoxy-6-(2-pyridyl)hex-2-ene (3 and 4) and 2-methoxy-6-(2-pyridyl)hex-1-ene (5) has been studied in hydrochloric acid solutions and acetic acid and biphosphate ion buffer solutions.The rate constant ratio for the hydronium ion catalysis of the neutral and positive forms of the substrates are 45.7, 44.9 and 15.7, respectively.The rate accelerations are interpreted in terms of intramolecular general acid catalysis and the results are discussed in relation to the suggested mechanism for hydrolysis of prostacyclin.
Copper(I)-Catalyzed Ketone, Amine, and Alkyne Coupling for the Synthesis of 2-Alkynylpyrrolidines and -piperidines
Van Beek, Wim E.,Van Stappen, Joren,Franck, Philippe,Abbaspour Tehrani, Kourosch
supporting information, p. 4782 - 4785 (2016/10/14)
A Cu(I)-catalyzed coupling of a ω-chloro ketone, a primary amine, and an alkyne is described. This protocol allows for the synthesis of α-quaternary carbons in 2-alkynyl-substituted N-heterocycles. The key step is the in situ generation of a cyclic ketiminium species, which has enhanced reactivity for alkynylation compared to acyclic ketiminium species.
β-Carotene autoxidation: Oxygen copolymerization, non-vitamin A products, and immunological activity
Burton, Graham W.,Daroszewski, Janusz,Nickerson, James G.,Johnston, James B.,Mogg, Trevor J.,Nikiforov, Grigory B.
supporting information, p. 305 - 316 (2014/05/06)
Carotenoids are reported to have immunological effects independent of vitamin A activity. Although antioxidant activity has been suggested as a basis of action, the ability of carotenoids to autoxidize to numerous non-vitamin A products with immunological activity is an alternative yet to be fully explored. We have undertaken a systematic study of β-carotene autoxidation and tested the product mixture for immunological activity. Autoxidation proceeds predominantly by oxygen copolymerization, leading to a defined, reproducible product corresponding to net uptake of almost 8 molar equivalents of oxygen. The product, termed OxC-beta, empirical formula C40H60O 15 versus C40H56 for β-carotene, contains more than 30% oxygen (w/w) and 85% β-carotene oxygen copolymers (w/w) as well as minor amounts of many C8-C18 norisoprenoid compounds. No vitamin A or higher molecular weight norisoprenoids are present. The predominance of polymeric products has not been reported previously. The polymer appears to be a less polymerized form of sporopollenin, a biopolymer found in exines of spores and pollen. Autoxidations of lycopene and canthaxanthin show a similar predominance of polymeric products. OxC-beta exhibits immunological activity in a PCR gene expression array, indicating that carotenoid oxidation produces non-vitamin A products with immunomodulatory potential.
Synthesis of novel analogs of acetyl coenzyme A: Mimics of enzyme reaction intermediates
Martin, David P.,Bibart, Richard T.,Drueckhammer, Dale G.
, p. 4660 - 4668 (2007/10/02)
An improved method for the synthesis of analogs of coenzyme A (CoA) and its thioesters, which are modified in the thiol or thioester moiety, has been developed using a combination of chemical and enzymatic reactions. The enzymes catalyzing the last two steps of CoA biosynthesis were used to prepare a CoA analog (Ic) in which an amide bond is replaced by a thioester bond and the thiol group is replaced by a methyl group. Reaction of Ic with a primary amine in aqueous solution results in aminolysis of the thioester linkage to form the desired CoA analog. Reaction with different amines permits the introduction of a variety of functional groups in place of the normal thiol or thioester group. This methodology has been used in the synthesis of five new analogs of acetyl-CoA in which the thioester sulfur is replaced by a methylene group and the acetyl group is replaced by carboxylate (14a), nitro (14b), carboxamide (14c), methyl sulfoxide (14d), and methyl sulfone (14e) groups. 14a-c were designed to mimic the possible enolate or enol intermediate in the reaction of citrate synthase and related enzymes. 14a and 14c are potent inhibitors of citrate synthase, with K(i) values 1000- and 570-fold lower than the K(m) for acetyl-CoA, respectively. CD titrations indicate that 14a and 14c have low affinity for citrate synthase in the absence of oxaloacetate, consistent with their recognition as enol or enolate analogs. 14b is a poor inhibitor of citrate synthase, with affinity slightly lower than that for acetyl-CoA. These results are consistent with generation of the enol form of acetyl-CoA as the nucleophilic intermediate in the reaction of citrate synthase. 14d and 14e were designed to mimic the tetrahedral intermediate or transition state in the reaction of chloramphenicol acetyltransferase and related acetyl-CoA-dependent acetyltransferases. Both compounds are poor inhibitors of chloramphenicol acetyltransferase, with affinities slightly lower than that of acetyl-CoA, indicating that these compounds are not good mimics of the enzyme-bound tetrahedral intermediate or transition state.
Synthesis and spectroscopic characterization of the doubly locked 9E,11Z retinal model systems 7E,13E-11,19-10,29-dimethanoretinal and its 13Z isomer
Groesbeek, M.,Robijn, G. W.,Lugtenburg, J.
, p. 92 - 98 (2007/10/02)
7E,13E-11,19-10,20-dimethanoretinal (1) and its 13Z isomer 2 were prepared from β-ionone, using the novel synthon 2-(diethoxyphosphinyl)-5,5-dimethoxyhexanenitrile.This synthon was also used to prepare 7E,9E,13E-10,20-methanoretinal (3) and its 13Z isomer 4 in high yield, starting from β-ionone.Spectroscopic analysis (mass, 1H and 13C NMR and UV/Vis) of these compounds is discussed.The introduction of the methano bridges leads to minimal steric and electronic changes.The photostationary state reached from 1 and 2 has the 13Z form 2 as the main constituent.This is one of the very few with a Z form as the main constituent of the photostationary state. 1 and 2 are very sensitive to acid-catalyzed isomerization of the 13-C=14-C double bond.The presence of the 11,19-methano bridge is responsible for this efficient Z-E isomerization.
