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Methylated Products (methylated + products)

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Chemistry	100%

Selected Abstracts

Improved Synthesis and Isolation of 2,- O -Methyladenosine: Effective and Scalable Enzymatic Separation of 2,/3,- O -Methyladenosine Regioisomers

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2009
Saúl Martínez-Montero
Abstract An efficient separation of a mixture of 2,/3,- O -methyladenosine regioisomers (1 + 2; 1:1) has been developed by selective enzymatic acylation using immobilized Pseudomonas cepacia lipase (PSL-C) in combination with acetonoxime levulinate as acyl donor. The 3,-hydroxy group of 2,- O -methyladenosine (1) was acylated with high selectivity (ca. 70,%), whereas an equal amount of 3,- O -methyladenosine (2) in the same solution resulted in minor acylation of 5,-hydroxy group (ca. 8,%). The differential behavior of both regioisomers towards enzymatic acylation allowed to develop a separation protocol. Upon extraction of the acylated products, the 3,- O -methyladenosine was isolated in 81,% yield and 97,% purity from the aqueous layer. Hydrolysis of acylated products in organic layer furnished 2,- O -methyladenosine in 67,% yield and 99,% purity. The separation process was successfully applied to the crude reaction mixture of methylated products (ca. 3:1 of 1/2) on 5-g scale. We also report on the use of methyl p -toluenesulfonate as a safe reagent for 2,- O -methylation of adenosine.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Chemoselectivity of the Reactions of Diazomethanes with 5-Benzylidene-3-phenylrhodanine

HELVETICA CHIMICA ACTA, Issue 9 2009
Martin
Abstract The reactions of 5-benzylidene-3-phenylrhodanine (2; rhodanine=2-thioxo-1,3-thiazolidin-4-one) with diazomethane (7a) and phenyldiazomethane (7b) occurred chemoselectively at the exocyclic CC bond to give the spirocyclopropane derivatives 9 and, in the case of 7a, also the C -methylated products 8 (Scheme,1). In contrast, diphenyldiazomethane (7c) reacted exclusively with the CS group leading to the 2-(diphenylmethylidene)-1,3-thiazolidine 11via [2+3] cycloaddition and a ,two-fold extrusion reaction'. Treatment of 8 or 9b with an excess of 7a in refluxing CH2Cl2 and in THF at room temperature in the presence of [Rh2(OAc)4], respectively, led to the 1,3-thiazolidine-2,4-diones 15 and 20, respectively, i.e., the products of the hydrolysis of the intermediate thiocarbonyl ylide. On the other hand, the reactions with 7b and 7c in boiling toluene yielded the corresponding 2-methylidene derivatives 16, 21a, and 21b. Finally, the reaction of 11 with 7a occurred exclusively at the electron-poor CC bond, which is conjugated with the CO group. In addition to the spirocyclopropane 23, the C -methylated 22 was formed as a minor product. The structures of the products (Z)- 8, 9a, 9b, 11, and 23 were established by X-ray crystallography. [source]

Historic review: Frederick Challenger, 1887,1983: chemist and biochemist

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2003
Thomas G. Chasteen
Abstract Frederick Challenger (1887,1983) lived a long life as a chemist and biochemist. He received a PhD for work with O. Wallach at the University of Göttingen in 1912 and a DSc from the University of Birmingham in 1920. After positions at Birmingham, UK, and Manchester, UK, he became Professor of Organic Chemistry at the University of Leeds, UK, in 1930, remaining as Head of the Department until 1953, when he retired as Emeritus Professor. He continued with scientific activity, publishing his final paper in 1978. Much of his work concerned the biological methylation of metalloids such as arsenic, selenium, and tellurium. He determined precise chemical structures for the methylated products and he established a role for adenosylmethionine in the process. An important finding was that the sulfonium compound, (CH3)2S+CH2CH2COO,, was present in several algae and on decomposition led to production of dimethylsulfide. This sulfonium compound was the first of this class to be found in a plant. He had many other wide-ranging interests, including the organic chemistry of compounds of bismuth and thallium. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Pd0 -Mediated Rapid Coupling between Methyl Iodide and Heteroarylstannanes: An Efficient and General Method for the Incorporation of a Positron-Emitting 11C Radionuclide into Heteroaromatic Frameworks,

CHEMISTRY - A EUROPEAN JOURNAL, Issue 45 2009
Masaaki Suzuki Prof.
Abstract The Pd0 -mediated rapid trapping of methyl iodide with an excess amount of a heteroaryl-substituted tributylstannane has been investigated with the aim of incorporating a short-lived 11C-labelled methyl group into the heteroaromatic carbon frameworks of important organic compounds, such as drugs with various heteroaromatic structures, in order to execute a positron emission tomography (PET) study of vital systems. The reaction was first performed by using our previously developed CH3I/stannane/[Pd2(dba)3]/P(o -CH3C6H4)3/CuCl/K2CO3 (1:40:0.5:2:2:2) system in DMF at 60,°C for 5,min (conditions A), however, the reaction gave low yields for various heteroaromatic compounds. Increasing the amount of phosphine ligand (conditions B) led to a significant improvement in the yield, but the conditions were still not suitable for a range of basic heteroaromatic structures. Use of the CuBr/CsF system (conditions C) also provided a result similar to that obtained under conditions B with an increased amount of the phosphine. Thus, pyridine and related heteroaromatic compounds remained less reactive substrates. The problem was overcome by replacing the DMF solvent with N -methyl-2-pyrolidinone (NMP). The reaction in NMP at 60,100,°C for 5,min using a CH3I/stannane/[Pd2(dba)3]/P(o -CH3C6H4)3/CuBr/CsF (1:40:0.5:16:2:5) combination (conditions D) gave the methylated products in yields of more than 80,% (based on the reaction of CH3I) for all of the heteroaromatic compounds listed in this study. Thus, the combined use of NMP and an increased amount of phosphine is important for promoting the reaction efficiently. The use of this general approach to rapid methylation has been well demonstrated by the synthesis of the PET tracers 2- and 3-[11C]methylpyridines by using [Pd2(dba)3]/P(o -CH3C6H4)3/CuBr/CsF (1:16:2:5) in NMP at 60,°C for 5,min, which gives the desired products in HPLC analytical yields of 88 and 91,%, respectively. [source]