Synthesis Davidson

Application of the Davidson oxazole synthesis to products of the Passerini reaction has expanded the usefulness of this well-known route <91LAll07>. The a-acyloxy ketones or a-acyloxy -keto esters employed in the Davidson synthesis are not readily available. However, the use of arylglyoxals as the carbonyl component of the Passerini reaction, along with cyclohexyl isocyanide and carboxylic acids, gives a wide variety of iV-cyclohexyl-2-acyloxy-3-aryl-3-oxopropionamides (151). Reaction of these intermediates with ammonium formate in acetic acid affords A -cyclohexyl-2,4-diaryl-5-oxazolecarboxamides (152) in fair yields (Scheme 69). 

The Davidson oxazole synthesis is the reaction of an acylated a-hydroxy carbonyl with an ammonium cation, typically ammonium acetate to yield oxazoles. The Davidson synthesis is also linear, as all three substituents are contained in the precursor. The reaction is most efficient in preparing 2,4,5-trisubstituted oxazoles, where C5 is aryl substituted. Yields suffer when preparing a 2,4-disubstituted or a mono-substituted oxazole. The COX-2 inhibitor tilmacoxib was prepared by Haruta in this manner. ... 

DAVIDSON Oxazole Synthesis Synthesis of Iriaryl oxazoles from a-hydroxyketones (benzoins)... 

Tri-O-acetyl-a-D-xylopyranosyl bromide106 (138) and N-tosyl-L-serine methyl ester107 (139) were condensed in the presence of Drierite and silver oxide, and then the O-acetyl and methyl ester groups were removed by treatment with sodium hydroxide, and the N-tosyl group by means of sodium in liquid ammonia, to give 140. Synthesis of this compound has also been described by other workers108-110 and the a-D an-omer by Brendel and Davidson.108... 

The remaining four chapters of the present volume involve topics new to the series. Two of them deal with specific groups of compounds (C. J. Moody on Azodicarbonyl Compounds and T. Sasaki on Heteroada-mantanes ) and two others deal with the Use of Transition Organome-tallic Compounds in Heterocyclic Synthesis (J. L. Davidson and P. N. Preston) and Sulfur Transfer Reagents (M. Davis). 

Finally the synthesis of inorganic-polymer composite membranes should be mentioned. Several attempts have been made to combine the high permeability of inorganic membranes with the good selectivity of polymer membranes. Furneaux and Davidson (1987) coated a anodized alumina with polymer films. The permeability increased by a factor of 100, as compared to that in the polymer fiber, but the selectivities were low (H2/O2 = 4). Ansorge (1985) made a supported polymer film and coated this film with a thin silica layer. Surprisingly, the silica layer was found to be selective for the separation mixture He-CH4 with a separation factor of 5 towards CH4. The function of the polymer film is only to increase the permeability. No further data are given. 

Winnik, F. M., Davidson, A. R., Hamer, G. K., and Kitano, H. Amphiphilic poly(A-isopropylacrylamide) prepared by using a lipophilc radical initiator Synthesis and solution properties in water. Macromolecules, 1992, 25, 1876-1880. 

Davidson, G., L. A. Blewett, K. T. Call, and SHADA Center. 2004. Public Program Crowd-out of Private Coverage What Are the Issues Research Synthesis Report No. 5. Available at www.rwJf.org/publications/synthesis/reportsjnd briefs/issue5.html. 

Davidson, B.S. Schumacher, R. W. (1993) Isolation and synthesis of caprolactins A and B, new caprolactams from a marine bactoium. Tetratedron, 49,6569-74. 

S. Sabesan, S. Neira, F. Davidson, J. Duus, and K. Bock, Synthesis and enzymatic and NMR-studies of novel sialoside probes Unprecedented, selective neuraminidase hydrolysis of and inhibition by C-6-(methyl)-Gal sialosides, J. Am. Chem. Soc. 776 1616 (1994). 

Ericsson, 1990), the synthesis of fluorescently labeled DNA probes (L. M. Smith et al., 19 8 5), as a label in homogeneous immunoassay systems (Nithipatikom and McGown, 1987), to investigate specific interactions of proteins with cells surfaces (Hochman et al., 1988), and as an important fluorescent tag of antibodies in immunohistochemical staining techniques (Davidson and Hilchenbach, 1990). 

Bobbink R, Hicks K, Galloway J, Spranger T, Alkemade R, Ashmore M, Bustamante M, Cinderby S, Davidson E, Dentener F, Emmett B, Erisman JW, Fenn M, Gilliam F, Nordin A, Pardo L, de Vries W (2010) Global assessment of nitrogen deposition effects on terrestrial plant diversity a synthesis. Ecol Appl 20 30-59... 

Davidson s synthesis consists of the cydization of a-acyloxyketones with ammonia or ammonium acetate to give 2,4,5-trisubstituted oxazoles. The Passerini reaction between arylglyoxals, carboxylic acids, and isocyanides afforded N-substituted 2-acyloxy-3-aryl-3-oxopropionamides 83 in high yields. Upon heating with an excess of ammonium acetate in acetic acid, compounds 83 were cydized to N,2,4-trisubstituted oxazole-5-carboxamides 84 in fair yields [59]. A large number of a-acyloxy-jS-ketoamides can be prepared by changing the reaction components, so the method provides straightforward access to a variety of oxazole-5-carboxamides (Scheme 2.30). 

Scheme 2.31. Synthesis of imidazole wo tandem Ugi-4CR/Davidson reactions.

Ameduri B, Boutevin B, Caporiccio G, Guida-Pietrasanta F, Ratsimihety A. Use of fluori-nated telomers in the preparation of hybrid silicones. In Hougham G, Davidson T, Cassidy P (Eds) Fluorinated Polymers Synthesis and Applications, Plenum, New York (in press)... 

Arimori, S., Davidson, M. G., Fyles, T. M., Hibbert, T. G., James, T. D., Kociok-Kohn, G. I., Synthesis and structural characterisation of the first bis(bora)calixarene a selective, bidentate, fluorescent fluoride sensor. Chem. Commun. 2004, 1640-1641. 

K3. King, M. P., Koga, Y., Davidson, M., and Schon, E. A., Defects in mitochondrial protein synthesis and respiratory chain activity segregate with the tRNALe (UUR> mutation associated with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes. Mol. Cell. Biol. 12, 480-490 (1992). 

Shipps GW Jr, Pryor KE, Xian J, Skyler DA, Davidson EH, Rebek J Jr, Synthesis and screening of small molecule libraries active in binding to DNA, Proc. Natl. Acad. Sci. USA, 94 11833-11838, 1997. 

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