Synthesis and structure of iso-C4B18H22

1983 ◽  
Vol 48 (1) ◽  
pp. 228-231 ◽  
Author(s):  
Zbyněk Janoušek ◽  
Jaromír Plešek ◽  
Bohumil Štíbr ◽  
Stanislav Heřmánek
Keyword(s):  
Nmr Spectra ◽  
Suggested Structure ◽  
A Minor

Iso-C4B18H22 isolated earlier as a minor by-product in the H2CrO4 oxidation of the C2B9H12(-) anion was prepared in 10% yield by thermolysis of 7,8-C2B9H13. The originally suggested structure, 3-(8'-nido-5,6-C2B8H11)-1,2-C2B10H11, is confirmed by the 11B NMR spectra.

scholarly journals Competitive Diels–Alder and ene addition of N-arylmaleimides to 7-dehydrocholesteryl acetate

1992 ◽  
Vol 70 (11) ◽  
pp. 2730-2744 ◽  
Author(s):  
William J. Leigh ◽  
Donald W. Hughes ◽  
D. Scott Mitchell
Keyword(s):  
Molecular Mechanics ◽  
Nmr Spectra ◽  
Benzene Solution ◽  
Diels Alder ◽  
Spectroscopic Techniques ◽  
Two Dimensional ◽  
A Minor ◽  
C Nmr ◽  
Alder Adduct ◽  
Ene Addition

Thermolysis of N-phenyl, N-para-biphenyl, and N-para, para′-terphenylmaleimide with 7-dehydrocholesteryl acetate in benzene solution at 200 °C yields mixtures of four cycloadducts in relative yields that are essentially independent of the maleimide substituent. The three major products are those of ene addition to C7 of the steroid with abstraction of the proton at C9 or C14. The α-endo-Diels-Alder adduct is formed as a minor product. The structures of the adducts have been elucidated on the basis of one- and two-dimensional 1H and 13C NMR spectroscopic techniques, including homonuclear 1H decoupling, NOE, 1H–1H COSY, heteronuclear 1H–13C shift correlation, and TOCSY 2-D experiments, and the results of molecular mechanics (MMX) calculations. The combination of these techniques has made it possible to almost completely assign the 1H and 13C NMR spectra for two of the ene adducts and the Diels–Alder adduct from reaction of 7-dehydrocholesteryl acetate with N-phenyl maleimide.

Fastigiatine, a lycopodium alkaloid with a new ring system

1986 ◽  
Vol 64 (5) ◽  
pp. 943-949 ◽  
Author(s):  
Robert V. Gerard ◽  
David B. MacLean ◽  
Romolo Fagianni ◽  
Colin J. Lock
Keyword(s):  
Mass Spectrum ◽  
Nmr Spectra ◽  
Minor Component ◽  
Ring System ◽  
Free Base ◽  
Relative Configuration ◽  
X Ray ◽  
H Nmr ◽  
Lycopodium Alkaloid ◽  
A Minor

Fastigiatine, C19H28N2O, is a minor component of the alkaloids of Lycopodiumfastigiatum R•Br•collected in New Zealand. Its structure and relative configuration have been resolved by an X-ray analysis of the free base. The pentacyclic ring system of fastigiatine has not been previously observed in the Lycopodium family of alkaloids or elsewhere. A proposal is presented for its derivation from the tetracyclic flabellidane ring system that is widely distributed among Lycopodium species. The mass spectrum and the 13C and 1H nmr spectra of fastigiatine are discussed.

scholarly journals Anomeric Spironucleosides of β-d-Glucopyranosyl Uracil as Potential Inhibitors of Glycogen Phosphorylase

Molecules ◽  
2019 ◽  
Vol 24 (12) ◽  
pp. 2327 ◽  
Author(s):  
Aggeliki Stathi ◽  
Michael Mamais ◽  
Evangelia D. Chrysina ◽  
Thanasis Gimisis
Keyword(s):  
Type 2 Diabetes ◽  
High Glucose ◽  
Nmr Spectra ◽  
Glycogen Phosphorylase ◽  
Biological Function ◽  
Chemical Shifts ◽  
Glucose Production ◽  
A Minor ◽  
Potential Inhibitors

In the case of type 2 diabetes, inhibitors of glycogen phosphorylase (GP) may prevent unwanted glycogenolysis under high glucose conditions and thus aim at the reduction of excessive glucose production by the liver. Anomeric spironucleosides, such as hydantocidin, present a rich synthetic chemistry and important biological function (e.g., inhibition of GP). For this study, the Suárez radical methodology was successfully applied to synthesize the first example of a 1,6-dioxa-4-azaspiro[4.5]decane system, not previously constructed via a radical pathway, starting from 6-hydroxymethyl-β-d-glucopyranosyluracil. It was shown that, in the rigid pyranosyl conformation, the required [1,5]-radical translocation was a minor process. The stereochemistry of the spirocycles obtained was unequivocally determined based on the chemical shifts of key sugar protons in the 1H-NMR spectra. The two spirocycles were found to be modest inhibitors of RMGPb.

scholarly journals Synthesis and Characterization of Aza-Trimetalla Tetrahedranes

1996 ◽  
Vol 51 (11) ◽  
pp. 1621-1626 ◽  
Author(s):  
Max Herberhold ◽  
Uwe Bertholdt ◽  
Bernd Wrackmeyer
Keyword(s):  
Nitrogen Atom ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Double Resonance ◽  
Synthesis And Characterization ◽  
Exchange Reactions ◽  
H Nmr ◽  
A Minor

The sulfimide complex Fe2(CO)6(μ-SNH) (1) reacts with Co2(CO)8 to form a 1:1 mixture of the known clusters FeCo2(CO)9(μ3-S) (2) and FeCo2(CO)9(μ3-NH) (3). The azatetrahedrane 3 may be used as a precursor for the synthesis of the new aza-trimetalla tetrahedranes Fe2Co(CO)9(μ-H)(μ3-NH) (5), CpMoFeCo(CO)8(μ3-NH) (6), CpNiFeCo(CO)6(μ3-NH) (7) and (CpNi)2Fe(CO)3(μ3-NH) (8) which were obtained from exchange reactions of 3 with Na2[Fe(CO)4], Na[CpMo(CO)3] and [CpNi(CO)]2. However, the reactions of 3 with Na2[Fe(CO)4] and Fe3(CO)12 gave Fe3(CO)9(μ-H)2(μ3-NH) (9) only as a minor product in addition to large amounts of Fe3(CO)9(μ-H)2(μ3-S) (10). The 1H NMR spectra of 3 and 5 - 9 show a broadened triplet for the NH proton between δ(1H) 8.21 and 9.53. Chemical shifts δ(14N) were determined most efficiently by heteronuclear 1H {14N} double resonance experiments. The δ(14N) values for aza-trimetalla tetrahedranes (-180 to -202) indicate delocalized bonding between the μ3-bridging nitrogen atom and the metal triangle.

(8Z)-1(15),8(9)-Trinervitadien-3α-ol from Nasutitermes nigriceps termites. The revised structure for a deffense compound of Trinervitermes gratiosus termites

1990 ◽  
Vol 55 (6) ◽  
pp. 1580-1585 ◽  
Author(s):  
Irena Valterová ◽  
Miloš Buděšínský ◽  
Jan Vrkoč ◽  
Glenn D. Prestwich
Keyword(s):  
Detailed Analysis ◽  
Nmr Spectra ◽  
Suggested Structure

The structure of (8Z)-1(15),8(9)-trinervitadien-3α-ol (IIa) was established by a detailed analysis of its NMR spectra for a trinervitane derived alcohol isolated from the species Nasutitermes nigriceps. The previously suggested structure I for the same compound isolated from Trinervitermes gratiosus is now revised.

Construction of the Side-Chain in 14β-Androst-5-ene Derivatives. Preparation of 14β-Pregnenolone

1994 ◽  
Vol 59 (12) ◽  
pp. 2691-2704 ◽  
Author(s):  
Ivan Černý ◽  
Miloš Buděšínský ◽  
Pavel Drašar ◽  
Vladimír Pouzar
Keyword(s):  
Nmr Spectra ◽  
Side Chain ◽  
Grignard Reaction ◽  
Diisobutylaluminum Hydride ◽  
Subsequent Oxidation ◽  
Hydride Reduction ◽  
Methylmagnesium Iodide ◽  
A Minor

Stepwise side-chain construction schemes leading to pregnane derivatives were tested in the 14β-androst-5-ene series. 6β-Methoxy-3α,5-cyclo-5α,14β-androstan-17-one (I) gave after methylenation and hydroboration the 17α-hydroxymethyl derivative III. Subsequent oxidation to the aldehyde VI, Grignard reaction with methylmagnesium iodide, and reoxidation led to the ketone VII and to the isomeric 17β-derivative VIII as a minor product. Final i-steroid cleavage of VII furnished the known 14β,17α-pregnenolone IX; the minor product VIII gave the 17β-isomer X. Alternatively, the ketone X was prepared from 6β-methoxy-3α,5-cyclo-5α,14β-androstan-17α-ol p-toluenesulfonate (XI) by cyanide substitution, diisobutylaluminum hydride reduction to the aldehyde XIV, and further as described for IX. The mass and NMR spectra of the four pregnenolone derivatives IX, X, XVIII, and XIX, isomeric in positions 14 and 17, were studied.

scholarly journals Anomeric Spironucleosides of β-D-Glucopyranosyl Uracil as Potential Inhibitors of Glycogen Phosphorylase

2019 ◽  
Author(s):  
Aggeliki Stathi ◽  
Michael Mamais ◽  
Evangelia D. Chrysina ◽  
Thanasis Gimisis
Keyword(s):  
Type 2 Diabetes ◽  
High Glucose ◽  
Nmr Spectra ◽  
Glycogen Phosphorylase ◽  
Biological Function ◽  
Chemical Shifts ◽  
Glucose Production ◽  
A Minor ◽  
Potential Inhibitors

Glycogen phosphorylase (GP) has been a target for compounds, inhibitors of GP that might prevent unwanted glycogenolysis under high glucose conditions and thus aim at the reduction of excessive glucose production from the liver, in the case of type 2 diabetes. Anomeric spironucleosides, such as hydantocidin, present a rich synthetic chemistry and possess important biological function. We have successfully applied the Suárez radical methodology to synthesize the first example of a 1,6-dioxa-4-azaspiro[4.5]decane system, not been previously constructed via a radical pathway, starting from 6-hydroxymethyl-β-D-glucopyranosyluracil. We have shown that in the rigid pyranosyl conformation the required [1,5]-radical translocation is a minor process. The stereochemistry of the spirocycles obtained were unequivocally determined based on the chemical shifts of key sugar protons in the 1H NMR spectra. The two spirocycles were found to be modest inhibitors of RMGPb.

195Pt- und 19F-NMR-Spektren der Fluoro-Chloro-Platinate(IV), [PtFnCl6-n]2-, n = 0-6 / 195Pt and 19F NMR Spectra of the Fluoro-Chloro-Platinates(IV), [PtFnCl6-n]2-, n = 0-6

1993 ◽  
Vol 48 (9) ◽  
pp. 1169-1174 ◽  
Author(s):  
E. Parzich ◽  
G. Peters ◽  
W. Preetz
Keyword(s):  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
19F Nmr ◽  
Complex Ions ◽  
19F Nmr Spectra ◽  
Trans Influence ◽  
Wide Range ◽  
A Minor ◽  
Cl Atom

The 10 complex ions of the system [PtFnCl6-n]2-, n = 0—6, including the three pairs of stereoisomers for n = 2, 3, 4 have been characterized by 195Pt and 19F NMR spectroscopy in CD2Cl2 solution. A wide range from 4731 ([PtCl6]2-) to 11816 ppm ([PtF6]2-) is covered by the clearly separated 195Pt resonances. The chemical shift δ(195Pt) depends nearly linearly on the sum of the electronegativities of the ligands. In accordance with increasing deshielding of the 195Pt nucleus by increasing coordination with F ligands an averaged major downfield shift of 1181 ppm per substitution of Cl by F is observed, while a minor averaged value of 354 ppm downfield is found for the trans/mer isomers in comparison to the related cis/fac isomers. Coupling with 19F results in characteristic 195Pt multiplets, with 1J(PtF) coupling constants for symmetric F—Pt—F axes of averaged 1890 Hz about 31% larger than 1J(PtF•) for asymmetric F•—Pt—Cl′ axes with averaged 1296 Hz. The data reflect the trans influence of the ligands. Highly resolved and expanded 195Pt spectra reveal clearly separated isotopomer signals with intensities according to the expected statistical ratios given by the natural abundance of 35Cl and 37Cl. For [Pt35Cln37Cl6-n]2- five distinct signals related to n = 6-2 with 0,18 ppm highfield shift per 37Cl atom have been reliably assigned. Resolved isotopomer peaks have also been observed for mer-[PtF335Cl3]2-/mer-[PtF335Cl237Cl]2- with 0,21 ppm and for [PtF535Cl]2/[PtF537Cl]2- with 0,32 ppm highfield shift per 37Cl atom, respectively. The 19F resonances of symmetric axes appear at higher field, in the range from —357 to —382 ppm, than those of asymmetric axes, from —266 to —287 ppm. Under high resolution compounds with inequivalent F nuclei show multiplets originating from homonuclear 2J(FF•) couplings of about 40 Hz.

Rating Post-Operative Backs (Part I)

1997 ◽  
Vol 2 (4) ◽  
pp. 1-3
Author(s):  
James B. Talmage
Keyword(s):  
Spinal Stenosis ◽  
Foot Drop ◽  
Neurogenic Claudication ◽  
Root Damage ◽  
Fourth Edition ◽  
Minor Strain ◽  
Injury Model ◽  
Strain Type ◽  
A Minor ◽  
Anterior Tibialis

Abstract The AMA Guides to the Evaluation of Permanent Impairment, Fourth Edition, uses the Injury Model to rate impairment in people who have experienced back injuries. Injured individuals who have not required surgery can be rated using differentiators. Challenges arise when assessing patients whose injuries have been treated surgically before the patient is rated for impairment. This article discusses five of the most common situations: 1) What is the impairment rating for an individual who has had an injury resulting in sciatica and who has been treated surgically, either with chemonucleolysis or with discectomy? 2) What is the impairment rating for an individual who has a back strain and is operated on without reasonable indications? 3) What is the impairment rating of an individual with sciatica and a foot drop (major anterior tibialis weakness) from L5 root damage? 4) What is the rating for an individual who is injured, has true radiculopathy, undergoes a discectomy, and is rated as Category III but later has another injury and, ultimately, a second disc operation? 5) What is the impairment rating for an older individual who was asymptomatic until a minor strain-type injury but subsequently has neurogenic claudication with severe surgical spinal stenosis on MRI/myelography? [Continued in the September/October 1997 The Guides Newsletter]

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