Synthesis and Conformation of 6-Amino-3,6-dideoxyhexono-1,6-lactams

2002 ◽  
Vol 67 (5) ◽  
pp. 622-644 ◽  
Author(s):  
Michaela Hamerníková ◽  
Jaroslav Havlíček ◽  
Hana Votavová ◽  
Karel Kefurt
Keyword(s):  
Nmr Spectroscopy ◽  
Chair Conformation ◽  
Cd Spectra ◽  
Equatorial Substituent

Three isomeric 6-amino-3,6-dideoxyhexono-1,6-lactams of D-ribo (1a), L-lyxo (2a) and L-arabino (3a) configuration were synthesized via the corresponding 6-azido-3,6-dideoxyhexoses starting from 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose. Conformation of lactams 1a, 2a and 3a and their tri-O-acetyl derivatives 1b, 2b and 3b was studied using NMR spectroscopy. CD spectra of the lactams 1a-3a, together with the D-xylo diastereoisomer 4a, were measured and interpreted according to semiempirical rules. NMR and CD measurements confirmed the chair conformation with an equatorial substituent on C-2 as prevailing for the all measured lactams.

Structural studies of digitoxin and related cardenolides by two-dimensional NMR

1990 ◽  
Vol 68 (2) ◽  
pp. 272-277 ◽  
Author(s):  
Torbjörn Drakenberg ◽  
Peter Brodelius ◽  
Deane D. McIntyre ◽  
Hans J Vogel
Keyword(s):  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Chair Conformation ◽  
Coupling Constants ◽  
Two Dimensional ◽  
Structural Studies ◽  
Solution Conformation ◽  
Phase Sensitive ◽  
Multiple Relay ◽  
C Nmr

The 1H and 13C NMR spectra of the cardenolides digitoxigenin, digoxigenin, digitoxin, and mono- and bis-digitoxigenin digitoxosides have been completely assigned by two-dimensional NMR spectroscopy. The techniques used include phase-sensitive COSY, multiple relay COSY, and carbon–proton correlation (HETCOR and HMQC) spectra. Various aspects of the solution conformation of the steroid moiety of digitoxin and digoxigenin could be determined from coupling constants and NOE difference experiments and they are indicative of an all-chair conformation. The carbohydrate rings in digitoxin and the mono- and bis-digitoxigenin digitoxosides are also in the chair conformation. Keywords: cardenolides, digitoxigenin, digitoxin, 2-dimensional NMR, conformational analysis.

Conformation studies of isomeric 1-acyloxy-2-(4-methoxybenzyl)-cyclohexanes by 1H NMR spectroscopy

1982 ◽  
Vol 47 (10) ◽  
pp. 2763-2767 ◽  
Author(s):  
Miloš Buděšínský ◽  
David Šaman ◽  
Zdeněk Wimmer
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Chair Conformation ◽  
Acetoxy Group ◽  
Cyclohexane Ring ◽  
H Nmr

The conformation of the cyclohexane ring and the p-methoxybenzyl substituent in the series of isomeric 1-acyloxy-2-(4-methoxybenzyl)cyclohexanes was studied by means of 1H NMR spectroscopy. In all the substances investigated the cyclohexane ring assumes chair conformation. trans-Isomers have both substituents in equatorial positions, while in cis-isomers the p-methoxybenzyl group is always equatorial and the hydroxy or acetoxy group axial.

N-Glycoside Complexes of Nickel(II); Probing Carbohydrate - Transition Metal Interactions

2009 ◽  
Vol 62 (3) ◽  
pp. 265 ◽  
Author(s):  
Dale Jones ◽  
Marcelis van Holst ◽  
Shigenobu Yano ◽  
Tomoaki Tanase ◽  
Janice Aldrich-Wright
Keyword(s):  
Chelate Ring ◽  
Chair Conformation ◽  
Nickel Atom ◽  
Cd Spectra ◽  
Metal Centre ◽  
Ring Conformation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Metal Interactions ◽  
Helical Configuration

Nickel(ii) complexes prepared from d- and l-arabinose (d-ara and l-ara) and 1,2-diaminoethane (en), [Ni(en-d-ara)2](ClO4)2·2H2O 1 and [Ni(en-l-ara)2](ClO4)2·2H2O 2 (where en-d-ara is 1-((2-aminoethyl)amino)-1-deoxy-d-arabinose) were synthesized and characterized by absorption spectroscopy, circular dichroism (CD), and X-ray crystallography. The CD spectra of 1 and 2 in the d–d transition region indicate a C2 chiral configuration around the metal centre. X-ray crystallography of 1 revealed that two 1-((2-aminoethyl)amino)-1-deoxy-d-arabinose ligands coordinate to the nickel atom in nearly C2 symmetry, through the C(2) hydroxy group of the arabinose moiety and two nitrogen atoms of the diamine in a meridional mode. This results in a Λ-C2-helical configuration around the metal centre. The arabinose ring adopts the rare α-1C4 chair conformation and the carbohydrate–chelate ring conformation is δ.

Stereochemistry of Substituted Isomeric 3-Oxa-7-aza-bicyclo[3.3.1]nonan-9-ones

1987 ◽  
Vol 42 (2) ◽  
pp. 221-228 ◽  
Author(s):  
Horst Küppers ◽  
Karl-F. Hesse ◽  
Ulrike Ashauer-Holzgrabe ◽  
Rolf Haller ◽  
Roland Boese
Keyword(s):  
Nmr Spectroscopy ◽  
Nitrogen Atom ◽  
Crystal Structures ◽  
Chair Conformation ◽  
Heterocyclic Ring ◽  
Boat Conformation ◽  
Bulky Substituent ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
X Ray

Abstract Two isomers of 7-methyl-9-oxo-2,4-diphenyl-3-oxa-7-aza-bicyclo[3.3.1]nonan-1,5-ethyl dicarboxylate (1a and 1b) were obtained by condensation of 2,6-diphenyl-1-oxa-4-oxo-cyclohexan-3,5-ethyl dicarboxylate with methylamine and formaldehyde. Their crystal structures were determined by X-ray diffraction. They crystallize in the triclinic space group P1̄ with (for 1a) a = 12.907(5), b = 11.223(4), c = 8.993(4) Å, α = 105.82(4), β = 100.14(5), γ = 97.35(4)°, and (for 1b) a = 16.400(7), b = 13.062(4), c = 11.336(2) Å, α = 94.19(3), β = 94.74(3), γ = 102.56(4)°. This investigation has shown that isomer 1a has the boat-chair conformation, and isomer 1b has the chair-chair conformation. The formation of la causes a configurational change of the phenyl substituents. The two species are characterized by NMR spectroscopy. - Another comparable bicyclononanone with a bulky substituent at the nitrogen atom has been synthesized and was investigated spectroscopically. This compound should have chair-boat conformation (with the boat conformation in the N-heterocyclic ring) whereas 1a has the boat conformation in the O-heterocyclic ring.

scholarly journals New Butenolide and Pentenolide from Dysidea cinerea

2013 ◽  
Vol 8 (12) ◽  
pp. 1934578X1300801
Author(s):  
Phan Van Kiem ◽  
Nguyen Xuan Nhiem ◽  
Ngo Van Quang ◽  
Chau Van Minh ◽  
Nguyen Hoai Nam ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Marine Sponge ◽  
2D Nmr ◽  
Cd Spectra ◽  
2D Nmr Spectroscopy ◽  
Chemical Methods ◽  
Nmr Data

Two new butenolide and pentenolide derivatives, dysideolides A-B, were isolated from the marine sponge Dysidea cinerea. Their structures were determined by the combination of spectroscopic and chemical methods, including 1D- and 2D-NMR spectroscopy, and CD spectra, as well as by comparing with the NMR data reported in the literature.

Anomalous α-effects due to methyl substitution in the half-chair conformation in carbon-13 NMR spectroscopy

1977 ◽  
Vol 18 (8) ◽  
pp. 699-702 ◽  
Author(s):  
Malick Sangaré ◽  
Bernard Septe ◽  
Guy Bérenger ◽  
Gabor Lukacs ◽  
Kazuo Tori ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Chair Conformation ◽  
Methyl Substitution

The anomeric effect in thio derivatives of benzocycloheptene

1992 ◽  
Vol 70 (10) ◽  
pp. 2650-2658 ◽  
Author(s):  
S. Désilets ◽  
M. St-Jacques
Keyword(s):  
Nmr Spectroscopy ◽  
Low Temperature ◽  
High Field ◽  
Chair Conformation ◽  
Anomeric Effect ◽  
Conformational Properties ◽  
Y Fragment ◽  
Derivatives Of ◽  
Twist Boat

The conformational properties of six thio derivatives of benzocycloheptene were studied by 1H and 13C high-field NMR spectroscopy in solution at low temperature. Both parent compounds 2 and 6, with sulfur at positions 3 and 1, respectively, were found to exist in the chair conformation. The 2-substituted derivatives of 2 (3: Y = OCH3 and 4: Y = Cl) revealed the presence of the Ca form only. In contrast, the 2-substituted derivatives of 6 (7: Y = OCH3 and 8: Y = Cl), with sulfur at position 1, showed mixtures of three conformers, namely Ca:Ce:TB (Ca = axial chair, Ce = equatorial chair, and TB = twist-boat), whose populations in CHF2Cl were, respectively, 93:5:2 and 85:12:3. The predominance of the Ca form in both series argues in favour of a strong anomeric effect in spite of the large departure from coplanarity (~35°) in the:—S—C—Y fragment of both 7 and 8. This noncoplanarity appears to weaken only slightly the n–σ* overlap characteristic of the endo-anomeric effect, contrary to earlier observations for the:—O—C—Y fragment in 5. The differences between the effects of O and S are discussed.

Structural characterization and thermal stability of Notothenia coriiceps metallothionein

2001 ◽  
Vol 354 (2) ◽  
pp. 291-299 ◽  
Author(s):  
Sabato D'AURIA ◽  
Vincenzo CARGINALE ◽  
Rosaria SCUDIERO ◽  
Orlando CRESCENZI ◽  
Daniela DI MARO ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Antarctic Fish ◽  
Metal Mobility ◽  
Effect Of Temperature ◽  
Amino Acid Residues ◽  
Cd Spectra ◽  
Multinuclear Nmr Spectroscopy ◽  
Notothenia Coriiceps ◽  
Mammalian Metallothioneins ◽  
Thermal Stability Of

Fish and mammalian metallothioneins (MTs) differ in the amino acid residues placed between their conserved cysteines. We have expressed the MT of an Antarctic fish, Notothenia coriiceps, and characterized it by means of multinuclear NMR spectroscopy. Overall, the architecture of the fish MT is very similar to that of mammalian MTs. However, NMR spectroscopy shows that the dynamic behaviour of the two domains is markedly different. With the aid of absorption and CD spectroscopies, we studied the conformational and electronic features of fish and mouse recombinant Cd-MT and the changes produced in these proteins by heating. When the temperature was increased from 20 to 90°C, the Cd-thiolate chromophore absorbance at 254nm of mouse MT was not modified up to 60°C, whereas the absorbance of fish MT decreased significantly starting from 30°C. The CD spectra also changed quite considerably with temperature, with a gradual decrease of the positive band at 260nm that was more pronounced for fish than for mouse MT. The differential effect of temperature on fish and mouse MTs may reflect a different stability of metal-thiolate clusters of the two proteins. Such a conclusion is also corroborated by results showing differences in metal mobility between fish and mouse Zn-MT.

scholarly journals Rhabdaprovidines D–G, Four New 6,6,5-Tricyclic Terpenoids from the Vietnamese Sponge Rhabdastrella providentiae

2018 ◽  
Vol 13 (10) ◽  
pp. 1934578X1801301 ◽  
Author(s):  
Duong Thi Dung ◽  
Dan Thi Thuy Hang ◽  
Nguyen Xuan Nhiem ◽  
Tran Hong Quang ◽  
Bui Huu Tai ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Cd Spectra ◽  
Esi Ms ◽  
Carbon Centers ◽  
Extensive Analysis ◽  
Chiral Carbon ◽  
Novel Structure ◽  
Ring Junction ◽  
The Absolute ◽  
Absolute Stereochemistry

Four new 6,6,5-tricyclic terpenoids, named rhabdaprovidines D-G (1–4), were isolated from the Vietnamese sponge Rhabdastrella providentiae. The structures of 1–4 were elucidated by extensive analysis of HR-ESI-MS and NMR spectroscopy. The absolute stereochemistry of compounds 3 and 4 were determined by both experimental and theoretical calculated circular dichroism (CD) spectra. Compounds 1, 2, and 4 contained trans-syn-trans 6,6,5-tricyclic nucleus meanwhile compound 3 possessed trans-syn-cis ring junction. Compound 4 displayed novel structure by the presence of five rings and nine chiral carbon centers in the isomalabaricane triterpene backbone.

Campnosperma Exudates. The Optically Active Long Chain 5-Hydroxycyclohex-2-Enones and Long-Chain Bicyclo[3.3.1]Nonane-3,7-Diones

1987 ◽  
Vol 40 (1) ◽  
pp. 79 ◽  
Author(s):  
SR Johns ◽  
JA Lamberton ◽  
TC Morton ◽  
H Suares ◽  
RI Willing
Keyword(s):  
Sodium Borohydride ◽  
Chair Conformation ◽  
Major Product ◽  
Optically Active ◽  
High Yield ◽  
Enol Ethers ◽  
Phenolic Components ◽  
Long Chain ◽  
Equatorial Substituent

Re-examination of the optically active long-chain 5-hydroxycyclohex-2-enones of Campnosperma species has confirmed the former structural assignments, except that in Tigaso oil both the 5- hydroxycyclohex-2-enones and the phenolic components contain a significant (35-40%) proportion of compounds with di-unsaturation in the C19-chain. Further study has been made of the conversion of (-)-endo-4-hexadecyl-l-hydroxybicyclo[3.3.l]nonane-3,7-dione (10) into a mixture of an optically inactive and optically active β- diketones. The major product from this reaction is (�)-5-(1-acetylheptadecy1)cyclohexane-1,3-dione (1l), which on methylation with diazomethane gives a mixture of two diastereoisomeric Omethyl ethers. These undergo cyclization to give a mixture of two epimeric 4-hexadecyl-l-methoxybicyclo[3.3.l]nonane-3,7-diones, (16) and (17), but reduction of the enol ethers followed by cyclization leads to an epimeric mixture of 4 hexadecylbicyclo [3.3.l]nonane-3,7-dion, (21) and (22). A detailed n.m.r. study of the bicyclo[3.3.l]nonane-3,7-diones, (10), (16), (17), (21), (22), (27) and (28), indicates that all have a chair-chair conformation, and also shows which of these compounds have an equatorial substituent, (10), (16), (21) and (27), and which an axial, (17), (22) and (28), at C4. Reduction of the bicyclo[3.3.1]nonane-3,7-diones with sodium borohydride gives oxaadamantane derivatives, and reduction of one diastereoisomeric β- diketone Omethyl ether gives a high yield of (�)-endo-4-hexadecyl-exo-3-methyl-2-oxabicyclo[3.3.l]nonane-7-one (25), the structure of which has been fully derived from n.m.r. study.

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