Mixture Of Erythro Research Articles

Enzymatic synthesis of ω-carboxy-β-hydroxy-( l)-α-amino acids

Commercially available ω-carboxy-aldehydes and glycine have been subjected to the catalytic action of an l-threonine aldolase from Escherichia coli to give the corresponding β-hydroxy-α-( l)-amino acids as a mixture of erythro/ threo epimers. Specifically, the reaction with glyoxylic acid ( 2) gave the epimeric β-hydroxy-( l)-aspartates ( t, e)-9 that could be isolated by ion-exchange chromatography in 67% yield. Following esterification and N-Boc protection, the two epimers could be isolated as pure compounds. Similarly, the aldolase-catalyzed addition of glycine to succinic semialdehyde ( 4) gave the expected mixture of β-hydroxy- l-α-aminoadipic acids ( t)-12 and ( e)-12 in 34% yield.

Acid hydrolysis kinetics and identification of erythro and threo α-ethyl ether derivatives of non-phenolic arylglycerol-β-syringyl ether lignin model compounds

Abstract Based on their hydrolysis behavior, NMR spectra of the erythro and threo forms of 3-(3,4-dimethoxy-phenyl)-2-(2,6-dimethoxyphenoxy)-3-ethoxypropan-1-ol (named VSE, i.e., α-ethyl ether derivative of veratrylglycerol-β-syringylether) were successfully assigned. A mixture of erythro and threo VSEs was treated at 90°C in pH 1.2 nitric acid solution. In order to assign them, the molar ratios of erythro and threo forms of 1-(3,4-dimethoxyphenyl)-2-(2,6-dimethoxy-phenoxy)propane-1,3-diol (named VS, i.e., veratrylglycerol-β-syringyl) ether given by each VSE were kinetically determined during the treatment. It was found that the inversion ratio at which the first VSE isomer gave erythro-VS was 0.73. Therefore, this isomer was identified as threo-VSE. In addition, from calculations using the least-squares method, the inversion ratio at which the other VSE isomer gave threo-VS was found to be >0.73. These values mean that threo-VSE yields 73% erythro- and 27% threo-VS, while erythro-VSE yields mainly threo-VS.

Selective Anodic Fluorination of Electrophilic Alkenes.

Abstract Anodic fluorination of some electrophilic alkenes (conjugated with electron-withdrawn groups), ethyl cinnamates, R C 6 H 4 CH CH CO 2 Et (R = H, CH 3 , CH 3 O, F and CF 3 ), cinnamonitrile, C 6 H 4 CH CH CN, phenyl stryryl ketone, and t -butyl styryl ketone using ammonium fluorides as the fluorine source and supporting electrolyte, in CH 2 Cl 2 as electrolytic solvent yields the expected vicinal difluoro compounds, as mixture of erythro and threo isomers. The anodic fluorination of phenyl 3,5-di- t -butyl-4-hydroxystyryl ketone yields two monofluoro compounds. A possible reaction mechanism is discussed.

Electrochemical Partial Fluorination of α,β‐Unsaturated Ketones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Selective anodic fluorination of electrophilic alkenes

Anodic fluorination of some electrophilic alkenes (conjugated with electron-withdrawn groups), ethyl cinnamates, R C 6H 4 CH CH CO 2Et (R = H, CH 3, CH 3O, F and CF 3), cinnamonitrile, C 6H 4 CH CH CN, phenyl stryryl ketone, and t-butyl styryl ketone using ammonium fluorides as the fluorine source and supporting electrolyte, in CH 2Cl 2 as electrolytic solvent yields the expected vicinal difluoro compounds, as mixture of erythro and threo isomers. The anodic fluorination of phenyl 3,5-di- t-butyl-4-hydroxystyryl ketone yields two monofluoro compounds. A possible reaction mechanism is discussed.

Enantiomeric discrimination in coordination of sulfoxides to platinum(II): X-ray structure of the kinetically over thermodynamically favoured erythro cis-dichloro-bis(methyl- p-tolylsulfoxide)platinum(II)

The erythro bis-sulfoxide complex cis-[PtCl 2R-S(O)MeTol pS-S(O)MeTol p] has been isolated, as the kinetically preferred product, in the reaction of K 2PtCl 4 with methyl- p-tolysulfoxide in water/methanol. The crystal and molecular structure of the title complex has been determined by X-ray diffraction methods and compared with those of the thermodynamically preferred threo species cis-[PtCl 2S(O)R′R″ 2] (R′Me, R n Ph or Tol p ). Crystal data: monoclinic, space group P2 1/n, a = 19.081(3), b = 5.992(1), c = 19.398(3) A ̊ , β = 119.05(2) a, Z = 4, R = 0.0355 . The kinetics of isomerization in chloroform of the erythro cis-[PtCl 2(S(O)MeTol p 2] to a 1:3 mixture of erythro and threo species has been investigated.

Synthesis of β-O-4 lignin model dimers and their chlorinated derivatives

The unknown lignin model dimers with hydroxymethyl group at the para position of the phenoxy moiety and their chlorinated derivatives (compounds 1–13, except 8) have been synthesized. During the preparation of 6 from 5, a byproduct was isolated and identified as 9. The compounds 4, 7, and 8 were obtained as a mixture of erythro and threo isomers in the ratio of about 5:4, estimated from their 13C NMR spectra, and the erythro isomer 8a was crystallized from the mixture. Chlorinated derivatives 12a (erythro) and 12b (threo) were also isolated. Their relative configuration was assigned on the basis of both 13C and 1H NMR spectroscopy.

A simple stereoselective synthesis of C 2-branched 2-deoxy-pentitols.

2,3-O-isopropylidene-D(+)-glyceraldehyde reacts with di- l-menthyl-malonate to give the penturonates 2a, and 3a in an erythro- threo 8.5:1 ratio. The C 2-branched sugars 2-deoxy-2-hydroxymethyl-3,4- erythro-pentitol 6 and 2-deoxy-2-hydroxymethyl-3,4- threo-pentitol 7 were obtained by submitting 2a and 3a to routine procedures. The same reaction, performed with di- d-menthylmalonate, resulted in a decreased diastereoselectivity, providing a 2.5:1 mixture of erythro and threo diastereomers.

Metabolism of 3,4-dimethoxycinnamyl alcohol and derivatives byCoriolus versicolor

3,4-Dimethoxycinnamyl alcohol (I) was actively metabolized by a white-rot fungus Coriolus versicolor in low nitrogen and high oxygen stationary cultures favouring the ligninolytic activity in the fungus. Substrate I was mainly oxidized to veratrylglycerol (III) which was a mixture of erythro and threo forms. Both isomers were degraded by cleavage between Cα and Cβ of the side chain to give veratraldehyde (VI), and (VI) was then reduced to veratryl alcohol (VII). A part of I was also metabolized via 1-(3,4-dimethoxyphenyl)-propane-3-ol (IV) and 1-(3,4-dimethoxyphenyl) propane-1,3-diol (VIII) by the fungus.

Metabolism of 3,4-dimethoxycinnamyl alcohol and derivatives by Coriolus versicolor

3,4-Dimethoxycinnamyl alcohol (I) was actively metabolized by a white-rot fungus Coriolus versicolor in low nitrogen and high oxygen stationary cultures favouring the ligninolytic activity in the fungus. Substrate I was mainly oxidized to veratrylglycerol (III) which was a mixture of erythro and threo forms. Both isomers were degraded by cleavage between Cα and Cβ of the side chain to give veratraldehyde (VI), and (VI) was then reduced to veratryl alcohol (VII). A part of I was also metabolized via 1-(3,4-dimethoxyphenyl)-propane-3-ol (IV) and 1-(3,4-dimethoxyphenyl) propane-1,3-diol (VIII) by the fungus.

A Reinvestigation of the Dichlorination of Thymidine

Abstract The reaction of thymidine with thionyl chloride in HMPA, reported1 to give pure 1-(3,5-dichloro-2,3,5-trideoxy-β-D-threo-pentofuranosyl)thymine, has been found to give a mixture of erythro and threo isomers. Upon reacting thymidine with thionyl chloride, according to the literature procedure,1 a product was isolated which melted 138–141°C [reported1 138–140°C] and gave one spot in CHCl3/ETOH (4:1) on Eastman silica gel sheets at Rf=0.6 [reported1 one spot at Rf=0.7 on Baker silica gel sheets]. However, the TLC of the product in neat ethyl acetate or CHCl3/MeOH (9:1) gave two spots. A sample was separated into pure components by flash chromatography2.

Synthesis of Oximes, Aziridines, and Allyl Alcohols Derived from Substituted l-Phenyl-l-nonen-3-ones as Potential Cytotoxic and Antitumor Agents

A number of nuclear-substituted l-phenyl-l-nonen-3-one oximes were synthesized. Reduction of several of these compounds with lithium aluminum hydride yielded the corresponding l-phenyl-2,3-epi- minononanes, shown by 100-MHz NMR spectroscopy to be the cis- geometrical isomers. When several ring-substituted 4-dimethylami- nomethyl-l-phenyl-l-nonen-3-ones were treated with hydroxylamine hydrochloride under forcing conditions, the product isolated was the corresponding oxime. Reaction under mild conditions led only to the isolation of the Michael addition product of the oxime in low yield. Reduction of some nuclear-substituted 4-dimethylaminomethyl-l-phenyl- 1 -nonen-3-ones with sodium borohydride led to the formation of the corresponding allyl alcohols, and the products were shown by 1H- and 13C-NMR spectroscopy to be the threo-isomers or, alternatively, a mixture of erythro- and threo- isomers. Reaction of phosphoric acid with one of the substituted allyl alcohols led to a diolefin, shown by NMR spectroscopy to be a mixture of (E, E)- and (E, Z)-isomers in a ratio of 65: 35.

The stereochemistry of the Peters reaction (RSO 2HgX → RHgX)

Thermal decomposition of either exo- or endo-2-norbornylsulfinatomercuric chloride ( exo-A or endo-A) in DMF at 100°C yields only exo-2-norbornylmercuric chloride. Under similar conditions, erythro-3,3-dimethylbutyl-1-sulfinatomercuric chloride-1,2- d 2 yields a 1 1 mixture of erythro- and threo-3,3-dimethylbutyl-1-mercuric chloride-1,2- d 2. endo-2-Norbornylmercuric chloride is not epimirized under the reaction conditions, and endo-A is recovered from partial decompositions without detectable epimerization. These results suggest that the product-forming step proceeds via a stereochemically labile intermediate. Although several qualitative experiments provide evidence against a free radical chain mechanism, the detailed pathway of the reaction has not been established.

The Hydroxyphenylation of Methylstyrenes with Phenylpalladium Chloride

Abstract The reaction of α- or β-methylstyrene with phenylpalladium chloride in aqueous acetone were studied. From cis- or trans-β-methylstyrene, a mixture of erythro and threo isomers of hydroxyphenylation products PhMeCHCHOHPh (VIa, VIb) and chlorophenylation products PhMeCHCHClPh (IVa, IVb) were obtained accompanying the phenylated olefins (I, II, and III). The main reaction product was the tertiary alcohol PhCH2C(OH)MePh (V). The reaction of α-methylstyrene with phenylpalladium chloride gave V exclusively. Phenylpalladium acetate and phenylpalladium bromide were used as phenylating agents. The yields of hydroxyphenylation products are in decreasing order: chloride>bromide>acetate.

Polyfluoroalkyl derivatives of nitrogen. Part XLII. Reaction of N-bromobistrifluoromethylamine with 1H-pentafluoropropene and some further studies on the thermal rearrangement of NN-bistrifluoromethyl-vinylamines

N-Bromobistrifluoromethylamine reacts with a 95 : 5 mixture of cis- and trans-1H-pentafluoropropene under free-radical conditions to give a high yield of a mixture of erythro- and threo-2-bromo-1,2,3,3,3-pentafluoro-NN-bistrifluoromethylpropylamine in the ratio 62 : 38. Dehydrobromination of the erythro-isomer affords a mixture of cis- and trans-1,2,3,3,3-pentafluoro-NN-bistrifluoromethylprop-1-enylamine in the ratio 38 : 62 whereas the threo-isomer yields the cis-olefin exclusively. The static pyrolysis of perfluoro-(NN-dimethylvinylamine) at 500 °C affords perfluoro-2-azapent-2-ene in reasonable yield, together with hexafluoroethane and other decomposition products. Pyrolysis in the presence of an excess of toluene gives trifluoromethane and only a low yield of the azapent-2-ene. Similarly 1,2-difluoro-NN-bistrifluoromethylvinylamine affords 4H-octafluoro-2-azapent-2-ene on pyrolysis, but 2-bromo-1,2-difluoro-NN-bistrifluoromethylvinylamine and NN-bistrifluoromethylvinylamine give mainly decomposition products.

Addition of free radicals to unsaturated systems. Part XXI. Reactions of 1H-pentafluoropropene with bromine, hydrogen bromide, and trifluoroiodomethane under free-radical conditions

1H-Pentafluoropropene, as a 95 : 5 mixture of cis- and trans-isomers, reacts with bromine in light to give a 75 : 25 mixture of the threo- and erythro-dibromides which on dehydrobromination affords a mixture of cis- and trans-1-bromo-1,2,3,3,3-pentafluoropropene. Photochemical reaction of the olefin with hydrogen bromide gives as the major products a mixture of erythro- and threo-1-bromo-1,2,3,3,3-pentafluoropropane and 2-bromo-1,1,1,2,3-pentafluoropropane in the ratio 70 : 16. The threo-adduct undergoes dehydrobromination to give a mixture of cis- and trans-1H-pentafluoropropene; the two other isomers afford the cis-olefin exclusively. Trifluoroiodomethane reacts with the olefin under photochemical or thermal conditions to give a mixture of erythro- and threo-1,1,1,2,3,4,4,4-octafluoro-2-iodobutane and 1,1,1,2,3-pentafluoro-3-iodo-2-trifluoromethylpropane in the ratios 56 : 40 : 4 and 50 : 43 : 7, respectively; dehydroiodination of the two former adducts separately yields trans-octafluorobut-2-ene and a 95 : 5 mixture of the cis- and trans-olefins, respectively.

Anodic oxidation. Part XII. Synthesis of 5-methoxy-5-phenylpentan-4-olide

Electrochemical oxidation of sodium (E)-5-phenylpent-4-enoate in methanol gives a mixture of erythro- and threo-5-methoxy-5-phenylpentan-4-olide.

Acid-catalysed reactions of methyl .BETA.-(34-dimethoxyphenyl) glycidate.

Methyl trans-β-(3,4-dimethoxyphenyl)glycidate was found to rearrange to methyl 3,4-dimethoxyphenylpyruvate in high yield in DMSO, DMF or HMPT solution in the presence of boron trifluoride etherate or sulfuric acid at room temperature. It was also revealed that the glycidate, when treated with boron trifluoride in methanol at room temperature, opened at the β-position to give methyl β-(3,4-dimethoxyphenyl)-α-hydroxy-β-methoxy-propionate in 94% yield, which was a mixture of erythro and threo isomers in the ratio of 1 to 2.