- α-haloenamines as reagents for the conversion of phosphorus oxyacids to their halogenated analogues
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Phosphorus oxyacids are converted to their halogenated analogues under mild conditions. α-Haloenamines are shown to be effective halogen transfer reagents affording good to high yields of the desired products at reaction times, in some cases, less than one minute. Georg Thieme Verlag Stuttgart.
- Norlin, Rikard,Juhlin, Lars,Lind, Per,Trogen, Lars
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p. 1765 - 1770
(2007/10/03)
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- METHYLPHOSPHINYL (Dmp): A NEW PROTECTING GROUP OF TYROSINE SUITABLE FOR PEPTIDE SYNTHESIS BY USE OF BOC-AMINO ACIDS
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Use of dimethylphosphinyl (Dmp) group as a side-chain phenolic OH protecting group of tyrosine in peptide synthesis was studied.The Dmp group is resistant to trifluoroacetic acid and hydrogenolysis and removed by fluoride ion or liquid HF.
- Ueki, Masaaki,Sano, Yoshiyuki,Sori, Ichiro,Shinozaki, Kozo,Oyamada,Hidekazu,Ikeda, Shigeru
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p. 4181 - 4184
(2007/10/02)
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- Evaluation of Phosphinic Acid Derivatives as Reagents For Amine Protection in Peptide Synthesis
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The results of a kinetic study of the acid-catalysed methanolysis of a series of N-(2-phenyl-ethyl)phosphinamides incorporating selected substituents on phosphorus have been evaluated in order to define the optimum reagent and conditions for amine protection of α-amino acids during peptide synthesis.
- Ramage, Robert,Atrash, Butrus,Hopton, David,Parrot, Maxwell J.
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p. 1217 - 1226
(2007/10/02)
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- Magnetic properties of anhydrous and hydrated dimethylphosphinates of manganese(II). The crystal and molecular structure of poly-bis(μ-dimethylphosphinato)diaquomanganese(II)
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The dimethylphosphinate of manganese(II), Mn2, and its dihydrate have been prepared and studied using magnetic susceptibility, differential scanning calorimetry,and electronic and vibrational spectroscopic methods.The dihydrate was obtained in crystalline form and a single crystal X-ray diffraction study revealed a polymeric structure.Crystals of poly-bis(μ-dimethylphosphinato)diaquomanganese(II) are monoclinic, a = 20.722(3), b = 4.8652(2), c = 11.0689(14) Angstroem, β = 102.209(7) deg, Z = 4, space group C2/c.The structure was solved by conventional heavy-atom methods and was refined by full-matrix least-squares procedures to R = 0.030 and Rw = 0.033 for 983 reflections with I >/= 3?(I).The structure consists of infinite centrosymmetric chains of Mn(II) atoms linked by double phosphinate bridges and extending along the crystallographic b axis.The water molecules are involved in both interchain and bifurcated intrachain hydrogen bonding (O...O = 2.734(2), 2.899(3) and 3.120(3) Angstroem).The coordination about Mn is slightly distorted octahedral with libration-corrected bond lenghts Mn-O(phosphinato) = 2.156(2) and 2.212(2), Mn-OH2 = 2.247(2) Angstroem.Magnetic susceptibility studies on the dihydrate from 300 to 4.2 K reveal a magnetic moment of ca. 5.9 BM over most of the range and give no evidence for significant magnetic exchange.The anhydrous compound, which is considered on the basis of indirect evidence to retain the double phosphinate bridged structure exhibited by the dihydrate, shows relatively strong antiferromagnetic behaviour.The data have been analyzed according to two theoretical models both of which employ the isotropic Heinsenberg Hamiltonian.The scaling model of Wagner and Friedberg gives J = -2.94 cm-1 and g = 2.02 and the interpolation scheme of Weng gives J = -2.69 cm-1 and g = 2.01.The manitude of the exchange coupling is considered in relation to that observed in related manganese compounds and possible reasons for the observed damping of the exchange on hydration are discussed.
- Cicha, Walter V.,Haynes, John S.,Oliver, Katherine W.,Rettig, Steven J.,Thompson, Robert C.,Trotter, James
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p. 1055 - 1062
(2007/10/02)
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- PHOSPHORIC, PHOSPHONIC, AND PHOSPHINIC ACID AMIDES AS BASES
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Potentiometric titration in nitromethane, IR- and NMR-spectroscopy were used to study the processes of protonation and H-bonding for a number of phosphoric, phosphonic and phosphinic acid amides. 12N)nP(O)R23-n(R1=Me, Et; R2=EtO, Me, Et; n=1-3) including 1,3,2-dioxa-, 1,3,2-oxazaphospholane and phosphorinane derivatives>.It was shown that in these compounds the center of the highest basicity is the oxygen of the phosphoryl group.
- Matrosov, E. I.,Kryuchkov, E. E.,Nifantyev, E. E.,Kozachenko, A. G.,Kabachnik, M. I.
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- Preparation of 3-substituted cephalosporins
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There is described a process for preparing an enamine of formula (IX): STR1 where R2 is a carboxylic acid protecting group and R3 is the residue of a carboxylic acid derived acyl group and where R5 and R6 are the same or different C1-4 alkyl or C7-10 aralkyl groups; or taken together with the adjacent nitrogen atom form a heterocyclic ring containing from 4 to 8 carbon atoms and optionally a further heteroatom selected from oxygen and nitrogen; by reacting a compound of formula (XII): STR2 with an amine of formula HNR5 R6, the reactant of formula (XII) being prepared by reaction of an appropriate enol derivative with a phosphorus reagent. The enamines of formula (IX) are useful in the preparation of 3-hydroxycephalosporins.
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