Synthesis of 8-homocastanospermine

2006 ◽  
Vol 84 (4) ◽  
pp. 534-539 ◽  
Author(s):  
Konrad Paśniczek ◽  
Dariusz Socha ◽  
Margarita Jurczak ◽  
Jolanta Solecka ◽  
Marek Chmielewski
Keyword(s):  
Nitrogen Atom ◽  
Carbon Atom ◽  
Malic Acid ◽  
Inhibitory Activity ◽  
Lactone Ring ◽  
Dipolar Cycloaddition ◽  
Sugar Chain ◽  
Terminal Carbon Atom ◽  
Intramolecular Alkylation ◽  
Chain Cleavage

The 1,3-dipolar cycloaddition of a five-membered cyclic nitrone derived from malic acid (4) and unsaturated D-threo-hexaldonolactone (1) leads to a single adduct 6, which can be transformed into the 8-homocastanospermine (13) via a sequence involving rearrangement of the six-membered lactone ring into the five-membered one, removal of the terminal carbon atom from the sugar chain, cleavage of the N—O bond, and the intramolecular alkylation of the nitrogen atom. The iminosugar (13) does not show any interesting inhibitory activity towards α- and β-glucosidases.Key words: iminosugars, homocastanospermine, nitrones, aldono-1,5-lactone, 1,3-dipolar cycloaddition, glucosidases.

Nucleophile/Electrophile Combinations in Aromatic Substitution: From Wheland to Wheland–Meisenheimer Intermediates Using Strongly Activated Arenes

Synthesis ◽  
2017 ◽  
Vol 49 (15) ◽  
pp. 3347-3356 ◽  
Author(s):  
Gabriele Micheletti ◽  
Carla Boga
Keyword(s):  
Nitrogen Atom ◽  
Carbon Atom ◽  
Short Review ◽  
Alkyl Halides ◽  
Aryl Halides ◽  
Aromatic Substitution ◽  
Aromatic Carbon ◽  
Isolation And Characterization ◽  
Acyl Halides

This short review provides an overview on the interaction between 1,3,5-triaminobenzene derivatives and different kinds of electrophiles. Due to the ambident reactivity of these nucleophiles (i.e., at the nitrogen atom of the substituents and at the aromatic carbon atom) different compounds can be obtained. Particular attention is devoted to the detection, isolation, and characterization of covalent intermediates of aromatic substitution, starting from Wheland intermediates until the first detection and characterization of Wheland–Meisenheimer intermediates.1 Introduction2 Reactions between 1,3,5-Triaminobenzene Derivatives and Charged Electrophiles2.1 The Proton as an Electrophile2.2 Arenediazonium Salts as Electrophiles3 Reactions between 1,3,5-Triaminobenzene Derivatives and Neutral­ Electrophiles3.1 Alkyl Halides as Electrophiles3.2 Acyl Halides and Sulfonyl Chlorides as Electrophiles3.3 Aryl Halides and Heteroaryl Halides as Electrophiles3.4 Polynitroheteroaromatics as Electrophiles4 Conclusion

Dative behavior of N-heterocyclic carbenes (NHCs) with selenium in Se-NHC compounds

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Munazzah Yaqoob ◽  
Mahvish Abbasi ◽  
Hira Anwar ◽  
Javed Iqbal ◽  
Mohammad Asad ◽  
...  
Keyword(s):  
Nitrogen Atom ◽  
Carbon Atom ◽  
Lone Pair ◽  
Heterocyclic Ring ◽  
Heterocyclic Carbenes ◽  
The Other ◽  
Donor Ligands ◽  
Important Research ◽  
Dative Bond ◽  
Back Bonding

Abstract N-heterocyclic carbenes (NHCs) are an eminent class of carbenes having a heterocyclic ring in which a divalent carbon atom is attached directly to a nitrogen atom. In the NHCs, the donation of lone pair is another important research in the dative bonding and not only in NHCs the dative bond plays a functionalized role in the other classes of complex formation like ylidones L → E ← L and carbones L → C ← L. M–NHC bond is L-M sigma-dative bond and NHCs are considered as strong sigma-donor ligands. The clear picture of the M–NHC bond can be better understood by M–NHC pi-interaction. M-L pi interaction is comprised of two steps. One is L → M sigma-donation and M → L π* back bonding. This dative donor nature of NHC and also its behavior in organoselenium is studied through DFT in which it’s optimized structure, bond lengths, molecular vibrations are calculated.

Hydroboration of acyclic allenes with disiamylborane

1969 ◽  
Vol 47 (6) ◽  
pp. 1083-1086 ◽  
Author(s):  
D. S. Sethi ◽  
G. C. Joshi ◽  
D. Devaprabhakara
Keyword(s):  
Carbon Atom ◽  
Transition State ◽  
Steric Effects ◽  
Electrophilic Attack ◽  
Terminal Carbon Atom ◽  
Central Carbon Atom ◽  
Central Carbon

The present investigation demonstrates the hydroboration of 1,2-nonadiene, phenylpropadiene, 3-phenyl-1,2-butadiene, 4,5-nonadiene, and tetramethylallene with disiamylborane. All the allenes except tetramethylallene underwent 100% conversion. Examination of the products indicated preferential electrophilic attack of boron on the least substituted terminal carbon atom in the case of 1,2-nonadiene, phenylpropadiene, 3-phenyl-1,2-butadiene, and on the central carbon atom in 4,5-nonadiene. In tetramethylallene boron, attack was exclusively on the central carbon atom. These results have been explained in terms of steric effects on a four-centered transition state.

scholarly journals Synthesis and crystal structures of two purpurin derivatives: 1,4-dihydroxy-2-propoxyanthraquinone and 2-butoxy-1,4-dihydroxyanthraquinone

2017 ◽  
Vol 73 (11) ◽  
pp. 1687-1691 ◽  
Author(s):  
Eric Bosch ◽  
Emily N. McClain
Keyword(s):  
Carbon Atom ◽  
Hydrogen Bonds ◽  
Sodium Hydride ◽  
Maximum Deviation ◽  
Independent Molecule ◽  
Asymmetric Unit ◽  
Terminal Carbon Atom ◽  
Butyl Group ◽  
Independent Molecules ◽  
Hydroxy Groups

The title compounds were obtained by deprotonation of 1,2,4-trihydroxyanthraquinone (purpurin) using sodium hydride followed by reaction with either 1-bromopropane or 1-bromobutane. 1,4-Dihydroxy-2-propoxyanthraquinone crystallizes as a 1:1 solvate from acetonitrile, C17H14O5·CH3CN. The anthraquinone core of the molecule is essentially planar and both hydroxy groups participate in intramolecular O—H...O (carbonyl) hydrogen bonds. The propyl chain is angled slightly above the plane of the anthraquinone moiety with a maximum deviation of 0.247 (2) Å above the plane for the terminal carbon atom. In contrast, 2-butoxy-1,4-dihydroxyanthraquinone, C18H16O5, crystallizes from nitromethane with two independent molecules in the asymmetric unit. The anthraquinone core of each independent molecule is essentially planar and both hydroxy groups on both molecules participate in intramolecular O—H...O(carbonyl) hydrogen bonds. The butyl chain in one molecule is also angled slightly above the plane of the anthraquinone moiety, with a maximum deviation of 0.833 (5) Å above the plane for the terminal carbon atom. In contrast, the butyl group on the second molecule is twisted out of the plane of the anthraquinone core with a torsion angle of 65.1 (3)°, resulting in a maximum deviation of 1.631 (5) Å above the plane for the terminal carbon atom.

scholarly journals Effect of the sugar chain of soluble recombinant CD59 on complement inhibitory activity

FEBS Letters ◽  
1996 ◽  
Vol 399 (3) ◽  
pp. 272-276 ◽  
Author(s):  
Hiroshi Suzuki ◽  
Noboru Yamaji ◽  
Akira Egashira ◽  
Kunio Yasunaga ◽  
Yuji Sugita ◽  
...  
Keyword(s):  
Inhibitory Activity ◽  
Sugar Chain

Intramolecular Diels-Alder Additions of Benzynes to Furans. Exploratory Studies

1986 ◽  
Vol 39 (4) ◽  
pp. 635 ◽  
Author(s):  
WM Best ◽  
D Wege
Keyword(s):  
Carboxylic Acid ◽  
Carbon Atom ◽  
Anthranilic Acid ◽  
Furan Ring ◽  
Alkoxy Group ◽  
Diels Alder ◽  
Ring Systems ◽  
Terminal Carbon Atom ◽  
Furan Moiety

A series of 3-alkoxyanthranilic acids, in which a furan ring is attached to the terminal carbon atom of the alkoxy group, has been prepared. When the chain linking the anthranilic acid and furan ring systems is three or four atoms long, decomposition of the derived diazonium chlorides generates the corresponding benzynes , which are efficiently trapped intramolecularly by the furan moiety. Diazotization of 2-amino-3-furfuryloxybenzoic acid, where the linking chain is two atoms long, results in fragmentation with the formation of 6-diazo-5- oxocyclohexa-1,3-diene-1-carboxylic acid.

Synthesis of Monobactams via the Diastereoselective Kinugasa Reaction

Synthesis ◽  
2018 ◽  
Vol 50 (10) ◽  
pp. 1991-2000 ◽  
Author(s):  
Kamil Kabala ◽  
Barbara Grzeszczyk ◽  
Bartłomiej Furman ◽  
Marek Chmielewski ◽  
Jolanta Solecka ◽  
...  
Keyword(s):  
Biological Activity ◽  
Nitrogen Atom ◽  
Carbon Atom ◽  
Bulky Substituent ◽  
Protecting Group ◽  
Acetylene Molecule ◽  
Cyclic Nitrones ◽  
Lactam Ring

The Kinugasa reaction between phthalimidoacetylene and cyclic nitrones derived from l-phenylglycine or l-serine and glyoxylic acid­, catalyzed by copper(I) chloride in the presence of triethylamine, is reported. The acetylene molecule approaches the nitrone exclusively anti to the bulky substituent next to the nitrogen atom to provide the cis-substituted β-lactam ring preferentially. The six-membered oxazinone ring can be easily opened, the phthaloyl residue can be transformed into a Boc protecting group, and substituents at the C-4 carbon atom and the nitrogen atom of the β-lactam ring can be easily removed or transformed into groups suitable for further synthesis of a variety of monobactam structures. Selected synthesized compounds were evaluated for their biological activity, showing interesting properties.

scholarly journals Hyperconjugative aromaticity and protodeauration reactivity of polyaurated indoliums

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Kui Xiao ◽  
Yu Zhao ◽  
Jun Zhu ◽  
Liang Zhao
Keyword(s):  
Nitrogen Atom ◽  
Carbon Atom ◽  
Electron Density ◽  
Cyclic Structure ◽  
Indole Ring

AbstractAromaticity generally describes a cyclic structure composed of sp2-hybridized carbon or hetero atoms with remarkable stability and unique reactivity. The doping of even one sp3-hybridized atom often damages the aromaticity due to the interrupted electron conjugation. Here we demonstrate the occurrence of an extended hyperconjugative aromaticity (EHA) in a metalated indole ring which contains two gem-diaurated tetrahedral carbon atoms. The EHA-involved penta-aurated indolium shows extended electron conjugation because of dual hyperconjugation. Furthermore, the EHA-induced low electron density on the indolyl nitrogen atom enables a facile protodeauration reaction for the labile Au-N bond. In contrast, the degraded tetra-aurated indolium with a single gem-dimetalated carbon atom exhibits poor bond averaging and inertness in the protodeauration reaction. The aromaticity difference in such two polyaurated indoliums is discussed in the geometrical and electronic perspectives. This work highlights the significant effect of metalation on the aromaticity of polymetalated species.

MINDO-Forces Study of Phenyl and Cyclopropyl Substituted Allyl Cations and Anions

1987 ◽  
Vol 42 (3) ◽  
pp. 297-304
Author(s):  
Hayfa M. Jarjis ◽  
Salim M. Khalil
Keyword(s):  
Carbon Atom ◽  
Energy Minimization ◽  
Phenyl Ring ◽  
Terminal Carbon Atom ◽  
Allyl Cation ◽  
Allyl Anions

MINDO-force calculations have been performed on phenyl and cyclopropyl substituted allyl cations and anions with complete energy minimization. It is found that the phenyl ring destabilizes the allyl cations when substituted at the terminal and at the center carbon atom of the cation, while the cyclopropyl ring stabilizes the allyl cation when substituted at the terminal carbon atoms, but destabilizes the cation when substituted at the center carbon atom of the cation. These results agree with the experimental ones. In the case of the allyl anions, it is found that the phenyl ring destabilizes the allyl anions when substituted on the terminal and on the center carbon atoms of the allyl anions, while the cyclopropyl ring stabilizes the allyl anion when substituted on the terminal carbon atom but destabilizes the anion when substituted on the center carbon atom. Also, it is found that both the phenyl and cyclopropyl rings are electron withdrawing when substituted on the allyl anions, while they are electron donating when substituted on the allyl cations.

Sign in / Sign up

Export Citation Format

Share Document