Revision of the structure of 3-methoxy-14α-hydroxy-D-homo-1,3,5-(10)-estratrien-17a-one. A simple 1H NMR method for the determination of configuration of hydroxy group in position 5 and/or 14 of the D-homo-steroid skeleton

1991 ◽  
Vol 56 (7) ◽  
pp. 1512-1524 ◽  
Author(s):  
Miloš Buděšínský ◽  
Alexander Kasal ◽  
Želimír Procházka ◽  
Huynh Kim Thoa ◽  
Soňa Vašíčková ◽  
...  
Keyword(s):  
Hydroxy Group ◽  
Chemical Shifts ◽  
Cotton Effect ◽  
Hydroxyl Group ◽  
H Nmr ◽  
Nmr Method ◽  
Synthetic Models ◽  
Steroid Skeleton

Eignerova and Prochazka found in 1974 the Cotton effect value for 3-methoxy-14α-hydroxy-D-homo-1,3,5(10)-estratrien-17a-one (Ia) to be Δε – 2.76.Calculation of the Δε value for this compound led, however, to a substantially lower value, which suggested the hypothesis that the compound was in fact rather an epimer with the hydroxy group in position 14β. This hypothesis was studied by means of 1H NMR spectra of synthetic models, using the changes of the chemical shifts of angular methyls, induced by in situ acylation of the angular hydroxyl with an α- or β-configuration with trichloroacetyl isocyanate (TAI). The observed TAI-acylation shifts on model compounds indicated the structure Ib with a 14b-configuration of the hydroxyl group. Indenpendent proof has been given by the synthesis of both 14-hydroxy epimers, Ia and Ib. A simple 1H NMR method is proposed for the determination of configuration of the hydroxyl in position 5 or 14 of D-homo-steroid skeleton.

Synthesis of a sequence-controlled in-chain alkynyl/tertiary amino dual-functionalized terpolymer via living anionic polymerization

2018 ◽  
Vol 9 (1) ◽  
pp. 108-120 ◽  
Author(s):  
Lincan Yang ◽  
Hongwei Ma ◽  
Li Han ◽  
Xinyu Hao ◽  
Pibo Liu ◽  
...  
Keyword(s):  
Anionic Polymerization ◽  
Kinetic Characteristics ◽  
Living Anionic Polymerization ◽  
Sequence Structure ◽  
H Nmr ◽  
Nmr Method ◽  
Tertiary Amino

A dual-functionalized sequence-defined terpolymer was synthesized via living anionic polymerization; meanwhile its kinetic characteristics and sequence structure were investigated in detail via the in situ1H NMR method.

scholarly journals Formation of highly quaternized N,N,N-trimethylchitosan: a chemoselective methodology in aqueous media

2019 ◽  
Vol 91 (3) ◽  
pp. 489-496 ◽  
Author(s):  
Youssouf D. Soubaneh ◽  
Steeven Ouellet ◽  
Caroline Dion ◽  
Jonathan Gagnon
Keyword(s):  
Biomedical Applications ◽  
Chemical Shifts ◽  
Aqueous Media ◽  
Acid Base ◽  
Specific Chemical ◽  
H Nmr ◽  
Low Degree ◽  
Simple Step ◽  
Carbonate Salt

Abstract N,N,N-Trimethylchitosan (TMC) represents a rare example of cationic polysaccharides and numerous studies have shown its potential in biological and biomedical applications. TMC with high degrees of quaternization (DQ) were synthesized from N-methylation of N,N-dimethylchitosan (DMC), which was obtained by reductive alkylation of high molecular weight chitosan in a simple step process and in good yields. The effects of base and solvents were evaluated on the quaternization reaction. The N-methylation of DMC was performed selectively by CH3I and carbonate in water where quaternization was achieved quantitatively with a low degree of O-methylation (17 %). Moreover, the greener procedure allows easy recovery and purification by conventional filtration as a carbonate salt, in which the anion can be exchanged by an acid-base reaction. Quantification of DQ involving 1H NMR integration of methyl peaks must be performed on protonated TMC. High field NMR spectra of TMC showed two specific chemical shifts for anomeric peaks (5.0 and 5.4 ppm) that can also be used for the determination of DQ. This latter method avoids the superimposition problems with other pyranosyl peaks.

Copolymerization of two bromine containing methacrylate monomers with methylmethacrylate. Determination of reactivity ratios by in situ quantitative 1H NMR monitoring

e-Polymers ◽  
2007 ◽  
Vol 7 (1) ◽  
Author(s):  
Ichim Ionut Cameliu ◽  
Marius Ciprian Rusu ◽  
Mihai Rusu ◽  
Popa Marcel ◽  
Christelle Delaite ◽  
...  
Keyword(s):  
Side Chain ◽  
Random Structure ◽  
Reactivity Ratios ◽  
Medical Implants ◽  
Propyl Methacrylate ◽  
H Nmr ◽  
Methacrylate Monomers ◽  
Methacrylic Monomers

AbstractAn important method used to make medical implants radiologically visible is based on introduction of radiopaque bromine or iodine containing methacrylic monomers. Thus, 2-(2-bromopropionyloxy) propyl methacrylate (BPPM) and 2-(2-bromoisobutyryloxy) propyl methacrylate (BIPM) were synthesized with the aim to use them as radiopaque agents. The free radical initiated copolymerization of BPPM and BIPM with methyl methacrylate (MMA) were performed directly in a thermostatic cell of the NMR spectrometer. The copolymer compositions obtained from 1H NMR spectra led to the determination of the reactivity ratios (rMMA = 1.08 ± 0.12; rBPPM = 1.01 ± 0.13 and rMMA = 0.95 ± 0.09; rBIPM = 0.95 ± 0.1). The reactivity ratios of these two monomers is similar to that of MMA suggesting that the length of the bromine containing monomers side chain does not affect significantly the reactivity of the methacrylic double bond. From the results we conclude the copolymers to have random structure.

Simple NMR Determination of 5α/5β Configuration of 3-Oxosteroids

2001 ◽  
Vol 66 (10) ◽  
pp. 1529-1544 ◽  
Author(s):  
Hana Chodounská ◽  
Miloš Buděšínský ◽  
Romana Šídová ◽  
Miroslav Šíša ◽  
Alexander Kasal ◽  
...  
Keyword(s):  
Nmr Spectra ◽  
Low Frequency ◽  
Simple Method ◽  
H Nmr ◽  
Steroid Skeleton ◽  
C Nmr

A simple method to distinguish the 5α- from the 5β-isomers of 3-oxosteroids based on low-frequency 1H NMR spectra was proposed. Additional 1H and 13C NMR characteristics were derived from the comparison of completely assigned spectra of the 5α- and 5β-isomers. The effect of substitution at different positions of steroid skeleton was evaluated on a series of isomeric 3-oxosteroids, prepared for this purpose.

Zusammensetzung von Rohsulfan, Nachweis der Sulfane H2S9 bis H2S35 Composition of Crude Sulfane Oil, Identification of the Sulfanes H2S9 to H2S35

1985 ◽  
Vol 40 (2) ◽  
pp. 263-272 ◽  
Author(s):  
Josef Hahn
Keyword(s):  
Narrow Range ◽  
Benzene Solution ◽  
Chemical Shifts ◽  
Upfield Shift ◽  
Downfield Shift ◽  
H Nmr ◽  
Intramolecular Hydrogen ◽  
Hydrogen Bondings ◽  
Nmr Signals

In benzene solution the position of the 1H NMR signals of sulfanes, H2Sn, strongly depends on the sulfur chain length and on the sulfane concentration. Under proper conditions all sulfanes in a mixture are characterized by well-resolved NMR signals showing a downfield shift with increasing length of the sulfur chain. The shift differences between the higher homologues ( n > 8 ) remain nearly constant, thus allowing the assignment of the signals up to H2S35 and the determination of the complete sulfane distribution in crude oils. In sulfane mixtures without solvent as well as in CS2 and CCl4 solutions, however, H2S8 shows the largest downfield shift. The signals of the higher sulfanes overlap in a narrow range at slightly higher field and cannot be characterized except for the CCl4 solution where an assignment up to H2S11 is possible. The chemical shifts are interpreted in terms of inter- and intramolecular hydrogen bondings. The upfield shift caused by benzene is attributed to the formation of H2Sn · benzene complexes.

The 1H NMR spectra and the conformation of 1,6-anhydro-β-D-hexopyranoses and their triacetates

1979 ◽  
Vol 44 (6) ◽  
pp. 1949-1964 ◽  
Author(s):  
Miloš Buděšínský ◽  
Tomáš Trnka ◽  
Miloslav Černý
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Shift Reagent ◽  
Point Of View ◽  
Coupling Constants ◽  
Lanthanide Shift Reagent ◽  
Pyranose Ring ◽  
H Nmr ◽  
Vicinal Coupling Constants

The 1H NMR spectra of 1,6-anhydro-β-D-hexopyranoses and their triacetates, measured in hexadeuteriodimethyl sulfoxide or deuteriochloroform, confirmed the existence of these compounds in 1C4(D) conformations, with the pyranose ring partly planarized in dependence on the configuration of the substituents in positions C(2), C(3) and C(4). The effects of the substituents on the chemical shifts and the adjusted relationship for the dependence of vicinal coupling constants on the torsion angle are discussed in detail from the point of view of the determination of the configuration and the conformation of 1,6-anhydro-β-D-hexopyranoses and their derivatives. The 1H NMR spectra of triacetates were also measured in the presence of the lanthanide shift reagent, tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione) europium (III) [Eu.(FOD)3].

Lupin alkaloids 6. Stereochemistry of bis-quinolizidine alkaloids with γ-oxo-α,β-enamine system

1994 ◽  
Vol 72 (1) ◽  
pp. 193-199 ◽  
Author(s):  
Tadeusz Brukwicki ◽  
Waleria Wysocka ◽  
Barbara Nowak-Wydra
Keyword(s):  
Conformational Changes ◽  
Chemical Shifts ◽  
Molecular Geometry ◽  
Coupling Constants ◽  
Hydroxyl Group ◽  
Coupling Constant ◽  
H Nmr ◽  
Time Signals ◽  
Low Sensitivity ◽  
First Time

1H nmr, 1H,1H and 1H,13C COSY, and 2D J-resolved spectra of multiflorine (1) and 13α-hydroxymultiflorine (2) in CDCl3 were taken. Some erroneously determined chemical shifts in 1 were corrected and for the first time signals in 2 were assigned. Most of the coupling constants in 1 and 2 were established. A coupling constant of H7–H17β and chemical shifts for H17β, C14, and C8 were used to define the conformational equilibrium of boat or chair forms in the C rings, in 1 and 2 in solution. The results obtained confirm the previous findings based on chemical shifts of C12: ca. 75 and 70% of the "boat" conformer in 1 and 2, respectively, at room temperature. Of all the criteria used, the H7–H17β coupling constant seems to be least sensitive to the influence of substituents at rings A and D. From the Haasnoot equation, torsion angles of HCCH in regions of molecular geometry featuring low sensitivity to conformational changes were calculated. The hydroxyl group at position 13α has a slight influence on the geometry of ring D.

Addition of the nitroxyl radical TEMPO to 1-naphthylketene: formation of an unusual adduct

1999 ◽  
Vol 77 (5-6) ◽  
pp. 806-809 ◽  
Author(s):  
Jennifer Carter ◽  
Michael H Fenwick ◽  
Wen-wei Huang ◽  
Vladimir V Popik ◽  
Thomas T Tidwell
Keyword(s):  
Nitroxyl Radical ◽  
Chemical Shifts ◽  
Wolff Rearrangement ◽  
Nmr Spectrum ◽  
X Ray ◽  
H Nmr ◽  
Naphthyl Ring ◽  
Nmr Signals ◽  
Very High

1-Naphthylketene (2), generated by thermal Wolff-rearrangement, is trapped in situ by 2,2,6,6-tetramethylpiridinyloxy radical (TEMPO, TO·) to form the adduct 1-naphthCH(OT)CO2T (4), whose structure is confirmed by an X-ray determination. The 1H NMR spectrum of 4 displays three CH3 groups with very high field chemical shifts (δ 0.10-0.47), and this is attributed to the location of these groups in the shielding region above the π system of the naphthyl ring. At -40°C, doubling of most of the 1H NMR signals occurs, and this is attributed to a freezing out of two conformations differing by rotation around the naphthyl—CH bond.Key words: ketene, TEMPO, restricted rotation, 1H NMR, conformational analysis, free radicals.

scholarly journals A simple and facile NMR method for the determination of hydrogen bonding by amide N–H protons in protein models and other compounds

2017 ◽  
Vol 41 (14) ◽  
pp. 6064-6066 ◽  
Author(s):  
Michael H. Abraham ◽  
Raymond J. Abraham
Keyword(s):  
Hydrogen Bonding ◽  
Chemical Shifts ◽  
Amide Group ◽  
Nmr Method ◽  
Protein Models

It is shown that measurements of the 1H chemical shifts of amide N–H protons in chloroform and in DMSO solvents are sufficient to determine the extent of hydrogen bonding of the N–H protons in a variety of compounds containing the amide group.

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