George Ryback
Royal Dutch Shell
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Biocatalysis and Biotransformation | 1995
Colette S. Matthews; John T. Rossiter; Douglas W. Ribbons; Philip John Geary; George Ryback; Robert J. Pryce
Biotransformation of benzene and derivatives has been used to accumulate meta-ring fission products of several catechols, including catechol, 3- and 4- methylcatechols, and 3- (trifluoromethyl) catechol. Dilute solutions of these yellow highly absorbing products were used to examine reaction conditions that affect their facile cyclizations with nitrogen nucleophiles, principally NH3. The effects of NH4+/NH3 concentration, pH and temperature on the non-enzymic cyclizations of 2-hydroxymuconic semialdehyde to 2-picolinate and its substituted derivatives have been characterised. As expected, the enzymic product from 3-(trifluoromethyl) catechol cyclised 20 times more slowly than that from 3-methylcatechol under identical reaction conditions. Most of the biological and chemical transformations were studied in very dilute solutions for the convenience of optical absorbance measurements. Because of the known sensitivity of the spectral shifts and extinction coefficients to minor changes in pH between 4 and 8 bo...
Journal of The Chemical Society-perkin Transactions 1 | 1994
Sheetal Handa; George J. Earlam; Phillip J. Geary; John E. Hawes; Gareth T. Phillips; Robert J. Pryce; George Ryback; Jeremy H. Shears
Two new routes to the important intermediate (–)-8 for the carbocyclic-based nucleosides are reported. The intermediate (–)-8 has also been synthesised in high. Enantiomeric excess via an enzymatic resolution of the racemic amide (+)-8 or an enzymatic enantiotopic hydrolysis of the meso diester 12.
Journal of The Chemical Society-perkin Transactions 1 | 1989
Carlos A. Pittol; Robert J. Pryce; Stanley M. Roberts; George Ryback; Vladimir Šik; Julian O. Williams
The title compound was treated with several dienophiles to give cycloadducts resulting from addition to the less hindered face of the molecule. An exceptional case was provided by N-ethylmaleimide which added in endo-fashion to both faces of the diene. 1,2-Isopropylidenedioxy-3-trifluoromethylcyclohexa-3,5-diene acted as a dienophile on addition to cyclopentadiene and underwent dimerization to give a stable [4 + 2] adduct.
Journal of The Chemical Society-perkin Transactions 1 | 1991
Mary F. Mahon; Kieren Molloy; Carlos A. Pittol; Robert J. Pryce; Stanley M. Roberts; George Ryback; Vladimir Šik; Julian O. Williams; John A. Winders
Various cycloadditions involving the cyclohexadiene derivatives 7–10 have been investigated. Diets–Alder reactions involving dimethyl acetylenedicarboxylate, nitrosobenzene and N-ethylmaleimide gave the adducts 11–14, 16–17 and 18–23 respectively. Hydrolysis of the tricyclic compound 11 with pig liver esterase provided the optically active monoester 15. Tropone, and three carbenes reacted with the diene 7 to give the polycyclic compounds 24 and 29, 31 and 33 as expected. The structure of the adduct 24 was elucidated by X-ray crystallography. The ester 32 was converted into the lactone 36 by way of an oxa-Cope rearrangement of the aldehyde 34. The dienes 7 and 8 reacted with diphenylketene in an unexpected fashion giving the enol ethers 27 and 28 as well as the expected [2 + 2] cycloaddition products 25 and 26.
Journal of The Chemical Society-perkin Transactions 1 | 1990
Wendy Downing; Regine Latouche; Carlos A. Pittol; Robert J. Pryce; Stanley M. Roberts; George Ryback; Julian O. Williams
The reactions of cis-1,2-isopropylidenedioxycyclohexa-3,5-diene (1) with two N-substituted maleimides, diphenylketene, dichlorocarbene and ethoxycarbonylcarbene are described. Selected reactions of the 3-triflucromsthyl-(2) and 3-fluoro-(3) analogues with these reagents are also reported.
Journal of The Chemical Society, Chemical Communications | 1990
Philip John Geary; Robert J. Pryce; Stanley M. Roberts; George Ryback; John A. Winders
Norbornadiene is oxidized by a Pseudomonad to give the diol (2)(35%) while 7-phenylnorbornadiene furnishes 3-norbornadienylcyclohexa-3,5-diene-1,2-diol (10)(41%) on incubation with the same organism; cyclization reactions involving the acetonide (15) have been investigated.
Proceedings of the Royal Society of London. Series B, Biological sciences | 1966
J. W. Cornforth; Rita H. Cornforth; C. Donninger; G. Popják; George Ryback; G. J. Schroepfer
FEBS Journal | 1970
János Rétey; Josef Seibl; Duilio Arigoni; J. W. Cornforth; George Ryback; Willem P. Zeylemaker; Cees Veeger
Journal of Chromatography A | 1976
George Ryback
Archive | 1987
George Ryback; John A. Schofield