scholarly journals Crystal structures of 4-{(E)-3-[(imino-λ5-azanylidene)amino]prop-1-enyl}-N,N-dimethylimidazole-1-sulfonamide and 2-[(imino-λ5-azanylidene)amino]-4-{(E)-3-[(imino-λ5-azanylidene)amino]prop-1-enyl}-N,N-dimethylimidazole-1-sulfonamide

2019 ◽  
Vol 75 (5) ◽  
pp. 695-699
Author(s):  
Lorenzo M. Cruz ◽  
Raakiyah Y. Moore ◽  
Marcela Torres Gutierrez ◽  
Apsara K. Herath ◽  
Carl J. Lovely ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Protecting Group ◽  
Azide Group ◽  
Imidazole Derivatives ◽  
Acidic Conditions ◽  
Allylic Azides

The structures of two azide containing imidazole derivatives are reported. Allylic azides are fairly reactive making them attractive starting compounds to convert into amides. The first, C8H12N6O2S, contains one azide group with an Nα—Nβ distance of 1.229 (2) Å and an Nβ—Nγ distance of 1.128 (2) Å. The second, C8H11N9O2S, contains two azide groups with an average Nα—Nβ distance of 1.249 (2) Å and an average Nβ—Nγ distance of 1.132 (2) Å. Each compound contains a bulky protecting group (dimethylaminosulfonyl) which can be easily removed under mildly acidic conditions.

Introduction of 4-Chlorophenyl: A Protecting Group for the Hydroxy Function

Synlett ◽  
2018 ◽  
Vol 29 (11) ◽  
pp. 1510-1516 ◽  
Author(s):  
Koichi Fukase ◽  
Yuji Otsuka ◽  
Toshihiro Yamamoto
Keyword(s):  
Hydroxy Group ◽  
Copper Catalyst ◽  
Pd Catalyst ◽  
Protecting Group ◽  
Acidic Conditions ◽  
Initial Conversion

4-Chlorophenyl ether was utilized as a new protecting group for the hydroxy function. This group was readily introduced to a sugar hydroxy group by using diaryliodonium triflate. Regioselective introduction of this protecting group at the vicinal cis-diol was achieved by using a copper catalyst and diaryliodonium triflate. This protecting group is stable under the Lewis acidic conditions of glycosylation, but it can be readily removed by the initial conversion into the corresponding 4-methoxyphenyl ether with use of a Pd catalyst, followed by oxidation with ammonium cerium (IV) nitrate [(NH4)2Ce(NO3)6] (CAN).

Total synthesis of (±)-9-deoxygoniopypyrone. Application of the iodocyclofunctionalization reaction of bold α-allenic alcohol derivatives

1998 ◽  
Vol 76 (1) ◽  
pp. 94-101 ◽  
Author(s):  
Richard W Friesen ◽  
Suzanne Bissada
Keyword(s):  
Total Synthesis ◽  
Primary Alcohol ◽  
Silyl Ether ◽  
Protecting Group ◽  
Acetylenic Ester ◽  
The Third ◽  
Vicinal Diol ◽  
Epoxide Opening ◽  
Vinyl Iodide ◽  
Acidic Conditions

The synthesis of ( ±)-9-deoxygoniopypyrone (1) from the α-allenic alcohol 5 is described. Iodocyclofunctionaliztion of the N-tosyl carbamate derivative of 5 using I2 and Ag2CO3 provided, in a highly diastereoselective and regioselective fashion, the vinyl iodo syn-vicinal diol 4. Two routes were explored in order to introduce the third stereogenic centre in the molecule. Reductive deiodination of the vinyl iodide and diastereoselective epoxidation of the derived acetonide14 using mCPBA provided a mixture of epoxides 15 and 16 (2:1) in which the desired threo diastereomer predominated. Alternatively, dihydroxylation of acetonide 14 (OsO4, NMO) yielded a mixture of diols 21 and 22 (2:3) which were separated after monosilylation (TBDMSCl) of the primary alcohol. The major silyl ether erythro diastereomer 24 was converted to the desired epoxide 15 by mesylation (MsCl, Et3N) and epoxide formation (TBAF) with inversion of stereochemistry. The minor threo diastereomer 23 was also converted to the desired epoxide 15 (TBAF; ArSO2Cl; NaOMe). Epoxide opening was effected with lithium acetylide and the resulting alkyne 27 was carbonylated (MeLi, ClCO2Me) to afford the α , β-acetylenic ester 28. Semi hydrogenation over Lindlar's catalyst followed by protecting- group removal under acidic conditions provided ( ±)-8-epigoniodiol 30. Finally, conversion of 30 to ( ±)-9-deoxygoniopypyrone 1 was effected under basic conditions (DBU).Key words: ( ±)-9-deoxygoniopypyrone, α-allenic alcohol, iodocyclofunctionalization, syn-diol.

scholarly journals Crystal Structures of two Imidazole Derivatives

2003 ◽  
Vol 393 (1) ◽  
pp. 75-82 ◽  
Author(s):  
P. Ambalavanan ◽  
K. Palani ◽  
M. N. Ponnuswamyand ◽  
R. A. Thirumuruhan ◽  
H. S. Yathirajan ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Imidazole Derivatives

A convenient protection for 4-oxopyrimidine moieties in nucleosides by the pivaloyl group

2010 ◽  
Vol 75 (1) ◽  
pp. 33-57 ◽  
Author(s):  
Michał Sobkowski
Keyword(s):  
Selective Removal ◽  
Protecting Group ◽  
Experimental Conditions ◽  
Reaction Proceeding ◽  
Mild Conditions ◽  
Acidic Conditions ◽  
Rapid Reaction

Application of the pivaloyl group as a protection for the N3 position of thymidine and uridine was investigated. Pivaloylation of thymidine is a very rapid reaction proceeding under mild conditions with excellent regioselectivity for sugar or thymine moiety, depending on the amines used. Several pivaloylated thymidine derivatives were obtained by treatment of unprotected thymidine with pivaloyl chloride under various experimental conditions. Stability of the N3-pivaloyl protecting group under basic and acidic conditions was evaluated and the conditions for its selective removal were found.

Pentamethylbenzyl esters of α-hydroxy acids and their use in depsipeptide synthesis

1968 ◽  
Vol 21 (5) ◽  
pp. 1327 ◽  
Author(s):  
FHC Stewart
Keyword(s):  
Amino Acids ◽  
Trifluoroacetic Acid ◽  
Hydroxy Acid ◽  
Ester Group ◽  
Protecting Group ◽  
Hydroxy Acids ◽  
Acidic Conditions ◽  
Crystalline Nature

Pentamethylbenzyl esters of several a-hydroxy acids have been prepared as possible intermediates in depsipeptide synthesis. Potentially useful features of pentamethylbenzyl as a carboxyl-protecting group are the crystalline nature of the esters, and the rapid cleavage of the group under mild acidic conditions. The glycollate, lactate, and mandelate were coupled with various protected amino acids to form crystalline aminoacyl hydroxy acid derivatives. Selective cleavage of the ester group in these compounds was readily effected with cold trifluoroacetic acid, and the products were used in the synthesis of some representative protected depsipeptides.

scholarly journals 8-Fluoro-N-2-isobutyryl-2′-deoxyguanosine: Synthesis and Reactivity

Molbank ◽  
10.3390/m1119 ◽  
2020 ◽  
Vol 2020 (1) ◽  
pp. M1119 ◽  
Author(s):  
Andrei Solodinin ◽  
James Helmkay ◽  
Samuel Ollivier ◽  
Hongbin Yan
Keyword(s):  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Ammonium Hydroxide ◽  
Dichloroacetic Acid ◽  
Protecting Group ◽  
Phase Synthesis ◽  
Phosphoramidite Chemistry ◽  
Acidic Conditions

3′,5′-O-Bis(tert-butyldimethylsilyl)-8-fluoro-N-2-isobutyryl-2′-deoxyguanosine was synthesized from 3′,5′-O-bis(tert-butyldimethylsilyl)-N-2-isobutyryl-2′-deoxyguanosine by the treatment with N-fluorobenzenesulfonimide. A similar fluorination reaction with 3′,5′-O-bis(tert-butyldimethylsilyl)-N-2-(N,N-dimethylformamidine)-2′-deoxyguanosine, however, failed to give the corresponding fluorinated product. It was found that 8-fluoro-N-2-isobutyryl-2′-deoxyguanosine is labile under acidic conditions, but sufficiently stable in dichloroacetic acid used in solid phase synthesis. Incorporation of 8-fluoro-N-2-isobutyryl-2′-deoxyguanosine into oligonucleotides through the phosphoramidite chemistry-based solid phase synthesis failed to give the desired products. Furthermore, treatment of 8-fluoro-N-2-isobutyryl-2′-deoxyguanosine with aqueous ammonium hydroxide did not give 8-fluoro-2′-deoxyguanosine, but led to the formation of a mixture consisting of 8-amino-N-2-isobutyryl-2′-deoxyguanosine and C8:5′-O-cyclo-2′-deoxyguanosine. Taken together, an alternative N-protecting group and possibly modified solid phase synthetic cycle conditions will be required for the incorporation of 8-fluoro-2′-deoxyguanosine into oligonucleotides through the phosphoramidite chemistry-based solid phase synthesis.

The crystal packing modes of three sterically overcrowded imidazole derivatives

1996 ◽  
Vol 52 (2) ◽  
pp. 369-375
Author(s):  
C. André ◽  
P. Luger ◽  
S. Lotz ◽  
W.-P. Fehlhammer
Keyword(s):  
Crystal Structures ◽  
Inclusion Compound ◽  
Crystal Packing ◽  
Layer Structure ◽  
Host Lattice ◽  
Imidazole Derivatives ◽  
Hexagonal Pattern ◽  
Yin And Yang

The crystal packing of racemic 4-cyclohexylamino-5-hydroxy-1,5-diphenyl-Δ3-imidazolin-2-one resembles the bilayered packing arrangements with alternating hydrophilic and hydrophobic layers observed in the crystal structures of lipids. The hydrophobic layers of the imidazolinone are built up individually by phenyl and cyclohexyl groups. In contrast, the corresponding 4-tert-butylamino derivative crystallizes optically resolved in a non-bilayer layer structure. This crystal packing is similar to the host-lattice of the inclusion compound formed by 9-(4-tert-butylphenyl)fluoren-9-ol and dioxane [Csöregh, Weber, Nassimbeni, Gallardo, Dörpinghaus, Ertan & Bourne (1993). J. Chem. Soc. Perkin Trans. 2, pp. 1775–1781]. The major building units of 4-tert-butylamino-1,5-diphenylimidazole are centrosymmetrical dimers in which the molecules display a `yin-and-yang'-like self-complementarity. The dimers pack in columns, which form a distorted hexagonal pattern.

scholarly journals Transformations of Griseofulvin in Strong Acidic Conditions – Crystal Structures of 2′-Demethylgriseofulvin and Dimerized Griseofulvin

2012 ◽  
Vol 7 (3) ◽  
pp. 1934578X1200700
Author(s):  
Barbara Lesniewska ◽  
Said Jebors ◽  
Anthony W. Coleman ◽  
Kinga Suwińska
Keyword(s):  
Hydrogen Bonding ◽  
Biological Activity ◽  
Hydrogen Bonds ◽  
Water Molecule ◽  
Crystal Structures ◽  
Π Interactions ◽  
Acidic Conditions

The structure of griseofulvic acid, C16H15ClO6, at 100 K has orthorhombic (P21212) symmetry. It is of interest with respect to biological activity. The structure displays intermolecular O–H···O, C–H···O hydrogen bonding as well as week C–H···π and π ···π interactions. In strong acidic conditions the griseofulvin undergoes dimerization. The structure of dimerized griseofulvin, C34H32Cl2O12·C2H6O·H2O, at 100 K has monoclinic (P21) symmetry. The molecule crystallized as a solvate with one ethanol and one water molecule. The dimeric molecules form intermolecular O–H···O hydrogen bonds to solvents molecules only but they interact via week C–H···O, C–H···π, C–Cl···π and π···π interactions with other dimerized molecules.

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