18815-74-2Relevant articles and documents
Rhodium-Catalyzed Desymmetrization of meso -Glutaric Anhydrides to Access Enantioenriched anti, anti -Polypropionates
Cochran, Brian M.,Henderson, Daniel D.,Thullen, Scott M.,Rovis, Tomislav
, p. 306 - 309 (2018)
An expedient desymmetrization of 3,5-dimethyl-4-alkoxyglutaric anhydrides to access anti, anti -polypropionates is described. The previously unknown anhydrides are rapidly assembled from readily available precursors. A Rh(I)· t -BuPHOX catalyst system was found to provide good yield and high selectivities. With these conditions, the trisubstituted anhydrides were desymmetrized with various alkyl zinc reagents to provide synthetically useful enantioenriched anti,anti -2,4-dimethyl-3-hydroxy-δ-ketoacids. An identical catalyst system also affords access to syn, syn -stereotriads as well as a partial kinetic resolution of a chiral anhydride.
Enantioconvergent and Regioselective Synthesis of Allenylsilanes by Nickel-Catalyzed C(sp2)-C(sp3) Cross-Coupling Starting from Racemic α-Silylated Propargylic Bromides
Xu, Yan,Yi, Hong,Oestreich, Martin
supporting information, p. 2194 - 2197 (2021/05/07)
A direct synthesis of enantioenriched allenylsilanes from racemic α-silylated propargylic bromides by an enantioconvergent nickel-catalyzed cross-coupling is reported. The high regioselectivity is governed by the bulky silyl group, and the C(sp2)-C(sp3) bond formation occurs exclusively at the γ-position of the propargyl electrophile. The level of enantioselection induced by a chiral Pybox ligand is moderate.
The Catalytic Alkylative Desymmetrization of Anhydrides in a Formal Synthesis of Ionomycin
Oberg, Kevin M.,Cochran, Brian M.,Cook, Matthew J.,Rovis, Tomislav
supporting information, p. 4343 - 4350 (2018/06/08)
The catalytic desymmetrization of anhydrides with zinc reagents provides access to deoxypolypropionate and polypropionate synthons. A synthesis of ionomycin was pursued in which three of the four fragments were assembled using this methodology. Two of the strategies (enol silane/oxocarbenium coupling and reductive cyclization) were not successful at installing the C23 stereocenter, but this stereochemical issue was overcome through a reduction/S N 2 approach. In addition to the synthesis of a protected diastereomer of ionomycin, the synthesis of a C17-C32 fragment constitutes a formal total synthesis.
Synthesis and Characterization of Urofuranoic Acids: In Vivo Metabolism of 2-(2-Carboxyethyl)-4-methyl-5-propylfuran-3-carboxylic Acid (CMPF) and Effects on in Vitro Insulin Secretion
Nagy, Edith,Liu, Ying,Prentice, Kacey J.,Sloop, Kyle W.,Sanders, Phillip E.,Batchuluun, Battsetseg,Hammond, Craig D.,Wheeler, Michael B.,Durham, Timothy B.
, p. 1860 - 1875 (2017/03/17)
CMPF (2-(2-carboxyethyl)-4-methyl-5-propylfuran-3-carboxylic acid) is a metabolite that circulates at high concentrations in type 2 and gestational diabetes patients. Further, human clinical studies suggest it might have a causal role in these diseases. CMPF inhibits insulin secretion in mouse and human islets in vitro and in vivo in rodents. However, the metabolic fate of CMPF and the relationship of structure to effects on insulin secretion have not been significantly studied. The syntheses of CMPF and analogues are described. These include isotopically labeled molecules. Study of these materials in vivo has led to the first observation of a metabolite of CMPF. In addition, a wide range of CMPF analogues have been prepared and characterized in insulin secretion assays using both mouse and human islets. Several molecules that influence insulin secretion in vitro were identified. The molecules described should serve as interesting probes to further study the biology of CMPF.
Overriding felkin control: A general method for highly diastereoselective chelation-controlled additions to α-silyloxy aldehydes
Stanton, Gretchen R.,Johnson, Corinne N.,Walsh, Patrick J.
, p. 4399 - 4408 (2010/06/14)
According to the Felkin-Anh and Cram-chelation models, nucleophilic additions to α-silyloxy aldehydes proceed through a nonchelation pathway due to the steric and electronic properties of the silyl group, giving rise to Felkin addition products. Herein we describe a general method to promote chelationcontrol in additions to α-silyloxy aldehydes. Dialkylzincs, functionalized dialkylzincs, and (E)-disubstituted, (E)-trisubstituted, and (Z)-disubstituted vinylzinc reagents add to silyl-protected α-hydroxy aldehydes with high selectivity for chelation-controlled products (dr of 10:1 to 20:1) in the presence of alkylzinc halides or triflates, RZnX. With the high functional group tolerance of organozinc reagents, the mild Lewis acidity of RZnX, and the excellent diastereoselectivities favoring the chelation-controlled products, this method will be useful in the synthesis of natural products. A mechanism involving chelation is supported by (1) NMR studies of a model substrate, (2) a dramatic increase in reaction rate in the presence of an alkylzinc halide, and (3) higher diastereoselectivity with larger alkyl substituents on the α-carbon of the aldehyde. This method provides access to chelation-controlled addition products with high diastereoselectivity previously unavailable using achiral organometallic reagents.
Process for the preparation of substituted fluorenes
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Page/Page column 22-23, (2008/06/13)
Methods for the preparation of fluorenyl-type ligand structures and substituted fluorenyl groups which may be employed in metallocene-type olefin polymerization catalysts. There is provided a 2,2′-dihalogen-diphenylmethylene having a methylene bridge conn
