Supposed acetyl migration from the 3β- to the 19-hydroxyl group in Δ5-steroids

1974 ◽  
Vol 27 (2) ◽  
pp. 323 ◽  
Author(s):  
DR Baigent ◽  
KG Lewis
Keyword(s):  
Chemical Shifts ◽  
Hydroxyl Group ◽  
Ether Group ◽  
Acetyl Migration

The product of monotritylation of 3β,19-dihydroxyandrost-5-en-17-one is the 3β-trityl ether, not the 19-trityl ether as previously proposed. In consequence the product of acetylation of the monotrityl ether is 19-acetoxy-3β-trityloxyandrost-5-en-17-one and thus acid-catalysed detritylation of this compound yields directly the 19-acetoxy derivative without the invoking of an acid-catalysed rearrangement. The isomeric 3β-hydroxy-19-trityloxyandrost-5-en-17-one has been prepared as well as a number of 3β-tritylated Δ5-steroids which have been used to study the influence of the trityl ether group upon p.m.r. chemical shifts in this series.

Configurationally dependent hydroxyl group effects on 13C nuclear magnetic resonance chemical shifts of olefinic carbons in cyclic six-membered allylic alcohols

1988 ◽  
Vol 66 (12) ◽  
pp. 3128-3131 ◽  
Author(s):  
Teodoro S. Kaufman
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Hydroxyl Group ◽  
Allylic Alcohols ◽  
Stereochemical Assignment ◽  
13C Nuclear Magnetic Resonance ◽  
Group Effects ◽  
Nuclear Magnetic

The differences in chemical shifts of olefinic carbons, Δδ(sp2), of pseudoequatorial and pseudoaxial six-membered allylic alcohols were correlated with the Δδ(sp2) values of their parent olefins. The results obtained reflect configurationally dependent substituent effects, the magnitude of which could be used for the stereochemical assignment of the hydroxyl group in these compounds.

A 51V NMR investigation of the interactions of aqueous vanadate with hydroxylamine

1997 ◽  
Vol 75 (7) ◽  
pp. 1002-1010 ◽  
Author(s):  
Sarah J. Angus-Dunne ◽  
Pradip C. Paul ◽  
Alan S. Tracey
Keyword(s):  
Chemical Shifts ◽  
Formation Constants ◽  
Hydroxyl Group ◽  
Methyl Groups ◽  
Trigonal Bipyramidal ◽  
Anionic Complexes ◽  
Acidic Conditions ◽  
A Charge ◽  
Neutral Conditions ◽  
Lower Ligand

The aqueous reactions of hydroxylamine and N-methylhydroxylamine with vanadate have been studied. Ligand, vanadium, and proton stoichiometries of the products have been obtained as have their formation constants. At lower ligand concentrations the predominant complex contains a single hydroxamido ligand and this has been assigned a five-coordinate, tetrahedral-like structure where the hydroxamido group is coordinated in a side-on fashion. Four bishydroxamido products were observed. These four complexes consisted of two distinct groups of two isomeric complexes each and have been assigned six-coordinate (tetrahedral-like) and seven-coordinate (trigonal bipyramidal-like) geometries. For the N-methylhydroxamido ligand, 10 bisligand products in 2 groups of 5 isomers each were observed. The additional products over the hydroxylamine situation arise from the relative orientations of the ligand methyl groups. For both ligands, the monoligand products carried a single negative charge and did not have a pKa, within the range of about 6–10. The bisligand products did not carry a charge under neutral conditions. The tetrahedral bisligand products could be protonated under acidic conditions (pKa ~ 6.6) but could not be deprotonated. In contrast, the trigonal bipyramidal products were not protonated under acidic conditions but could give up a proton under basic conditions (pKa ~ 7.4) to form anionic complexes. The relative orientations of the ligands and also the number of methyl groups and their relative orientations in the complex have a significant influence on the 51V chemical shifts. One additional complex was observed to form and was assigned to an ester-like product formed by reaction at the hydroxyl group. Keywords: vanadate, complexes, hydroxylamine, methylhydroxylamine, peroxovanadate.

Synthesis and nuclear magnetic resonance spectra of some partially acylated β-D-glucopyranosides

1968 ◽  
Vol 46 (15) ◽  
pp. 2485-2493 ◽  
Author(s):  
A. P. Tulloch ◽  
A. Hill
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Trimethylsilyl Ether ◽  
Ether Group ◽  
Nuclear Magnetic Resonance Spectra ◽  
The Difference ◽  
Derivatives Of ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The synthesis of ten new partially acylated derivatives of methyl β-D-glucopyranoside, all with an acyl group at C-6, is described. The nuclear magnetic resonance spectra of these compounds, and of a number of related derivatives, have been measured using pyridine, acetone-d6, and deuteriochloroform as solvents. When OH-4 is acylated, the H-6 signals are at higher field (by 0.1–0.3 p.p.m.) than when OH-4 is not acylated, but this effect is not observed when OH-3 is acylated. When a trimethylsilyl ether group is introduced at C-4 the difference between the chemical shifts of the H-6 protons (δA –δB) increases markedly. Estimation of JBX and JAX (where B is the H-6 proton at higher field and X is H-5), from spectra obtained using acetone-d6 and pyridine as solvents, shows that JBX < JAX when there is an acyl group at C-4 but JBX > JAX when there is no acyl group at C-4.

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.

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.

SPIN ECHOES IN ALCOHOLS AND DERIVATIVES

1956 ◽  
Vol 34 (7) ◽  
pp. 653-667 ◽  
Author(s):  
G. J. B. Crawford ◽  
J. S. Foster
Keyword(s):  
Chemical Shifts ◽  
Spin Echo ◽  
Larmor Frequency ◽  
Molecular Structures ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hydroxyl Group ◽  
Primary Alcohols ◽  
Field Evidence ◽  
Spin Echo Technique

The spin echo technique has been employed to measure the relative chemical shifts and the indirect spin–electron–spin coupling constants between protons at different structural sites in ethyl, propyl, isopropyl, butyl, isobutyl, and amyl alcohols and certain of their derivatives at a Larmor frequency of 29.0 Mc./s. The separation between the two r-f. pulses applied to the sample increases regularly in accurately known steps which are controlled electronically. Thus the frequencies modulating the echo envelope have been readily measured with a precision as high as 4% in favorable cases. Relative chemical shifts found by slow passage experiments have been checked with higher accuracy, particularly for the primary alcohols. Encouraged by the implications of these earlier data, we have here analyzed the longer hydrocarbon chains on the basis of the theoretical computations of Hahn and Maxwell for only two groups of non-equivalent protons. This more precise investigation confirms the assumptions made as to where the major shifts and couplings do and do not exist in the molecular structures. In the halide molecules, it is found that the observed relative chemical shifts are linearly proportional to the paramagnetic fields arising from the valence orbits of the halogens polarized by the external field. Evidence for the particular J-coupling to the hydroxyl group in the alcohols suggests that this bond is effectively stronger in the heavier molecules which are only slightly soluble in water.

The characterization of primary, secondary, and tertiary vanadate alkyl esters by 51V nuclear magnetic resonance spectroscopy

1988 ◽  
Vol 66 (10) ◽  
pp. 2570-2574 ◽  
Author(s):  
Alan S. Tracey ◽  
Michael J. Gresser
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Chemical Shifts ◽  
Hydroxyl Group ◽  
Resonance Spectroscopy ◽  
Low Field ◽  
Nuclear Magnetic

A variety of alkyl vanadates has been studied by 51V nuclear magnetic resonance spectroscopy. It was found that the equilibrium constant for condensation of vanadate with alcohols is insensitive to whether the hydroxyl group is primary, secondary, or tertiary. These products, however, have characteristic vanadium chemical shifts that allow assignment of nmr signals to the appropriate ester. It was also found that chemical shifts are additive in the sense that the chemical shifts of the esters ROVO3H− are one half the chemical shift of the diesters (RO)2VO2− when those shifts are given relative to −559 ppm. This effect is independent of whether the signals are to high or low field of −559 ppm and the additivity extends to mixed ligand systems. This value of −559 ppm is close but not equal to the chemical shift of the vanadate monoanion, H2VO41−, which is at −561 ppm. These results are at variance with arguments concerning the effects of ligand bulkiness on chemical shifts of vanadium(V) complexes.

A Proton Magnetic Resonance Study of the Influence of Base Ionization on the Conformation of Pseudouridine

1972 ◽  
Vol 50 (7) ◽  
pp. 766-774 ◽  
Author(s):  
Roxanne Deslauriers ◽  
Ian C. P. Smith
Keyword(s):  
Hydrogen Bond ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Deuterium Oxide ◽  
Coupling Constants ◽  
Hydroxyl Group ◽  
Basic Solution ◽  
Hydroxymethyl Group ◽  
Ultraviolet Spectra

The proton magnetic resonance spectra of alkaline deuterium oxide solutions of α-pseudouridine (α-ψ), β-pseudouridine (β-ψ), and 1-(β-D-ribofuranosyl)-cyanuric acid (β-CAR) are analyzed to explore the possibility that conformational changes are responsible for the unusual ultraviolet spectra of β-ψ at high pH. The largest change in ribose ring conformation due to increased alkalinity is observed in β-ψ; the ribose ring, although interconverting between various puckered forms, shows a slight preference for the 2′-endo and 3′-exo conformations. There is also a preference by α-ψ and β-ψ for the gauche-gauche rotamers about the exocyclic C4′–C5′ bond; this preference is not shown by β-CAR. No change occurs in the chemical shifts of the protons of α-ψ and β-ψ on going from neutral or acidic to basic solution. Increasing temperature to 60 °C causes no significant change in either coupling constants or chemical shifts. Comparison of chemical shifts observed in β-ψ with those found in β-CAR leads us to believe that the base remains in the anti conformation with respect to the ribose ring and is therefore incapable of forming a hydrogen bond with the exocyclic hydroxyl group as had been postulated previously to explain anomalous ultraviolet spectral data. A weak hydrogen bond between the 5′-hydroxymethyl group and the 5–6 double bond remains as a plausible explanation for the unusual ultraviolet spectra.

Sign in / Sign up

Export Citation Format

Share Document