1,3-Oxazolidin-4-ones. Synthesis and configuration of cis and trans isomers

Mixtures of cis and trans 1,3-oxazolidin-4-ones were obtained by cyclodehydration, in the presence of p-toluenesulfonic acid or boron trifluoride etherate, of lactamide and N-methyl-lactamide with aromatic and aliphatic aldehydes. The products were separated by column (silica) chromatography and their configurations were determined.     

Novel syntheses of cis and trans isomers of combretastatin A-4.

A high-yielding, two-step stereoselective synthesis of the anticancer drug (Z)-combretastatin A-4 (1) has been devised. The method uses the Perkin condensation of 3,4,5-trimethoxyphenylacetic acid and 3-hydroxy-4-methoxybenzaldehyde followed by decarboxylation of the cinnamic acid intermediate using copper and quinoline. The iodine-catalyzed isomerization of the Z isomer 1 results in complete conversion to the E isomer. The Suzuki cross-coupling of an aryl boronic acid and vinyl bromide has also been successfully employed to produce both Z and E isomers of combretastatin A-4 stereoselectively. Both methods are far superior to the current five-step Wittig synthesis in which both isomers are produced nonstereoselectively.     

Chromatographic analysis of cis/trans carotenoid isomers.

Cis/trans configurations of carotenoids are known to effect the biochemistry of carotenoids in certain situations. Methodology for separating carotenoid cis/trans isomers is of importance to nutritionists and food scientists because cis isomers of provitamin A carotenoids have lower provitamin A activities than the all-trans form. Traditional food processing and preservation methods, especially thermal treatments, induce the formation of cis isomeric forms. However, many challenges, are apparent for identifying and analyzing cis/trans isomers present in foods and other biological tissues. The development of current chromatographic methods for the separation of carotenoid cis/trans isomers is reviewed. For the separation of beta-carotene isomers, most procedures employ either Ca(OH)2 or Vydac C18 columns. In general, polymeric C18 columns allow for the detection of cis carotenes, while monomeric C18 columns provide for some separation of certain xanthophylls. The main cis isomers detected in foods are the 13-cis and 9-cis forms, although other forms have also been found (mainly 15-cis and various di-cis isomers). More studies involving the metabolism and physiological consequences of cis/trans isomers in the diet are needed. However, due to limitations in current techniques, further method development in the area of separation, detection and quantitation of cis/trans carotenoid isomers will be required.     

Controlled synthesis of cis or trans isomers of 1,3-disubstituted tetrahydroisoquinolines and 2,5-disubstituted pyrrolidines

[reactions: see text] The stereoselective outcome of Pd(II)- or Ag(I)-catalyzed intramolecular N-alkylation to afford 1,3-disubstituted 1,2,3,4-tetrahydroisoquinolines was examined. In the absence of additional substituents, Pd(II) allows a facile access to the cis isomers, while Ag(I) favors formation of the trans isomers. The same observation was made for the synthesis of 2,5-disubstituted pyrrolidines. Possible reasons for the observed stereoselectivities are discussed.     

Vistas in the field of 1,3-oxathiolan-5-ones: Synthesis and chemical reactivity

This review covers many reports of the applications of multicomponent domino reactions (MDRs) in the synthesis of novel stereocontrolled mercapto-heterocycles from the 1972 up to the end of 2016. The reported approaches were employed for modifications of the oxathiolanone core for new construction of a mercapto-heterocycles scaffold from mercaptoacetyl transfer agent with various reagents.     

Derivate des 1,3-Dioxolan-4-ons und des 1,3-Oxathiolan-5-ons

Zusammenfassung Es wird die Synthese einer Anzahl von 1,3-Dioxolan-4-onen und 1,3-Oxathiolan-5-onen beschrieben und über eine pharmakologische Prüfung dieser Substanzen berichtet.Herrn Prof. Dr.J. W. Breitenbach mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Preparation of 4-substituted 1,3-oxathiolan-5-ones via the sulphenium ion intermediate generated by the pummerer rearrangement

4-Substituted 1,3-oxathiolan-5-ones have been synthesized via the Pummerer rearrangement from the S-oxide of the parent molecule. The 4,5-dione is obtained in the presence of pyridine N-oxide.     

PMR spectra of derivatives of the cis and trans isomers of 4-amino-3-hydroxythiophane

The PMR and proton magnetic double resonance (PMDR) spectra were obtained for five cis and trans isomer pairs of substituted 4-amino-3-hydroxythiophanes. A comparison of the PMR parameters of the cis and trans isomers made it possible to formulate the characteristic differences in their spectra. On the basis of the data obtained, the trans configuration is proposed for the ethoxycarbonylamino and hydroxy groups in 4-ethoxycarbonylamino-3-hydroxy-3-cyanothiophane, the configuration of which has not been previously determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp.316–319, March, 1971.     

Vibrational spectra and structures of the cis and trans isomers of linear benzindigo

The resonance Raman and IR spectra of the cis and trans isomers of linear benzindigo were investigated, and the frequencies of the vibrations of the multiple bonds were assigned. The large splitting of the frequencies of the symmetrical (_s) and asymmetrical (_as) vibrations of the carbonyl groups of the trans isomer of benzindigo and indigo is associated with the electronic interaction of these groups in the process of vibration.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 501–504, April, 1981.     

A convenient synthesis of 1,3-oxazolidin-4-ones and 1,3-oxazin-4-ones

1,3-Oxazolidin-4-ones and 1,3-oxazin-4-ones were synthesized by formal cyclocondensation of imines with α- or β-hydroxy acids.     

1,3-二甲基-4-芳氧乙酰基-5-吡唑啉酮类化合物的合成

以双乙烯酮和甲基肼为原料合成1,3-二甲基-5-吡唑啉酮, 再在氢氧化钙催化下,以异丙醇为溶剂, 与芳氧基乙酰氯缩合制得一纱列标题化合物. 并用红外, 紫外, 质谱研究了它们的结构 . 测定了它们对于家稗的生物活性, 探讨了除草活性与结构的关系.     

Synthesis and properties of 5-methylene-1,3-dioxolan-4-ones

A general method, which consists in the dehydroxypropanoic of 5-chloromethyl-1,3-dioxolan-4-ones, is proposed for the synthesis of 5-methylene-1,3-dioxolan-4-ones. With respect to their structure, the synthesized compounds are simultaneously derivatives of acrylic acid and vinyl ethers.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1316–1318, October, 1985.     

顺、反二氟乙烯分子结构和稳定性的ab initio研究

The geometries and their harmonic frequencies of the difluoroethylene isomers were gradient optimized using ab initio methods at the different levels. High-level methods give very good structural parameters in comparison to experiment. The single energy of stable structure and the frontier orbital energy gap were calculated using MP4SDTQ/6-311++G(2df,2pd) method, and it is found that the single energy of stable structure of cis isomer is lower than that of trans isomer. This is consistent with the experimental result. Mulliken population analyses were also performed to interpret the internal nature of cis preference of difluoroethylene isomers.     

Isomeric Diruthenium Complexes Bridged by Deprotonated Indigo in cis and trans Configuration

The doubly deprotonated form L^2? of indigo=H₂L can bind two [Ru(acac)₂] complex fragments in the cis ( 1 ) and trans configuration ( 2 ), as evidenced from crystal structure analysis. While the latter type of N,O; N ^’ ,O ^’ coordination has been observed earlier, for example, with [Ru(bpy)₂]²⁺, leading to two equivalent six‐membered ring chelates, the cis arrangement in 1 is observed here for the first time in a dinuclear complex, producing one five‐membered ring chelate with N,N ^’ coordination and one seven‐membered chelate with O,O ^’ coordination. The different structures of the isomers result in differing electrochemical and spectroelectrochemical (EPR, UV‐Vis‐NIR) responses for various accessible charge states 1 ⁿ and 2 ⁿ, n=–, 0, +, 2+. The associated electronic structures were analyzed by DFT (structures, spin density) and TD‐DFT calculations (electronic transitions), revealing mainly metal‐based reduction but largely indigo ligand‐based oxidation of both neutral precursors.