Differential reactivity of carbohydrate hydroxyls in glycosylations. II. The likely role of intramolecular hydrogen bonding on glycosylation reactions. Galactosylation of nucleoside 5′-hydroxyls for the syntheses of novel potential anticancer agents

1994 ◽  
Vol 72 (11) ◽  
pp. 2225-2238 ◽  
Author(s):  
Dennis M. Whitfield ◽  
Stephen P. Douglas ◽  
Ting-Hua Tang ◽  
Imre G. Csizmadia ◽  
Henrianna Y.S. Pang ◽  
...  
Keyword(s):  
Anticancer Agents ◽  
Hydrogen Abstraction ◽  
Intramolecular Hydrogen Bonding ◽  
Nucleophilic Attack ◽  
Side Reactions ◽  
Silver Triflate ◽  
Differential Reactivity ◽  
Intramolecular Hydrogen ◽  
Hydroxy Groups ◽  
First Time

Contrary to expectations, many primary hydroxy groups are completely unreactive in glycosylation reactions, or give the desired glycosides in very low yields accompanied by products of many side reactions. Hydrogens of such primary hydroxyls are shown to be intramolecularly hydrogen bonded. Intermediates formed by nucleophilic attack by these hydroxyls on activated glycosylating agents may resist hydrogen abstraction. This resistance to proton loss is postulated to be the origin of the observed unreactivity. It is shown that successful glycosylations take place under acidic conditions under which such hydrogen bonds cease to exist. Accordingly, direct galactosylations of the normally unreactive 5′-hydroxyls of nucleosides were accomplished for the first time with a galactose trichloroacetimidate donor in chloroform under silver triflate promotion. It is noted that such galactosylated anticancer nucleosides may have improved biological specificity.

Synthesis of 2', 6'-Dihydroxychalcones by Using Tetrahydropyran-2-yl and Trialkylsilyl Protective Groups; the Crystal Structure Determination of 2',6'-Dihydroxy-2,4,6-trimethoxychalcone

1989 ◽  
Vol 42 (7) ◽  
pp. 1103 ◽  
Author(s):  
CO Miles ◽  
L Main ◽  
BK Nicholson
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Silyl Ether ◽  
X Ray ◽  
Protective Groups ◽  
Intramolecular Hydrogen ◽  
First Time ◽  
Mild Acid

Two improved general routes to 2′,6′-dihydroxychalcones are described in which the final step is protective-group removal from O 2′ under mild acid conditions. The first involves base-catalysed condensation of benzaldehydes with 2′-hydroxy-6′-tetrahydropyran-2-yloxyacetophenone, the second ring-opening of 5-hydroxyflavanones with 1,8-diazabicyclo[5.4.0]undec-7-ene in the presence of a trialkylchlorosilane to trap out the chalcone as a bis silyl ether. Chalcones prepared by the first route are 2',6'-dihydroxychalcone (1), and its 4-methoxy (2), 3,4-dimethoxy (3), 3,4,5-trimethoxy (4), and 2,4,6-trimethoxy (5) derivatives. The 4-chloro derivative (6) and the chalcone from hesperetin are prepared by the second method. .The X-ray crystal structure of 2',6'-dihydroxy-2,4,6-trimethoxychalcone (5), the first for a 2',6′-dihydroxychalcone, is reported, the hydrogen involved in intramolecular hydrogen-bonding between the carbonyl and phenolic oxygens being located for the first time for any 2'-hydroxychalcone derivative. The O 6' involved in the intramolecular hydrogen-bonding is also hydrogen-bonded intermolecularly to the hydrogen of the other (2'-)hydroxy group of a neighbouring molecule in the lattice. 13C n.m.r. data are the first reported for a series of 2',6'-dihydroxychalcones.

1,1-Diphenylbutane-1,3-diol: the First Structurally Characterized Example of an Intramolecularly Hydrogen-Bonded Open-Chain 1,3-diol

1996 ◽  
Vol 49 (11) ◽  
pp. 1251
Author(s):  
CF Carvalho ◽  
DP Arnold ◽  
RC Bott ◽  
G Smith
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Orthorhombic Space Group ◽  
Open Chain ◽  
Space Group ◽  
A Cell ◽  
Intramolecular Hydrogen ◽  
Hydroxy Groups ◽  
Hydrogen Bonded

The crystal structure of the asymmetric 1,3-diol 1,1-diphenylbutane-1,3-diol has been determined and refined to a residual R of 0.039 for 795 observed reflections. Crystals are orthorhombic, space group P212121, with four molecules in a cell of dimensions a 9.625(4), b 16.002(3), c 8.834(3) Ǻ. The compound is unique among the known crystallographically characterized open-chain 1,3-diols in having only intramolecular hydrogen bonding involving the hydroxy groups [O-- -O 2.602(5) Ǻ].

catena-Poly[[(2,9-dimethyl-1,10-phenanthroline-κ2 N,N′)lead(II)]-di-μ-2-hydroxybenzoato-κ3 O 1,O 1′:O 2;κ3 O 2:O 1,O 1′]

2007 ◽  
Vol 63 (11) ◽  
pp. m2678-m2678 ◽  
Author(s):  
Xiao-Peng Xuan ◽  
Pei-Zheng Zhao
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Packing ◽  
Rotation Axis ◽  
Intramolecular Hydrogen Bonding ◽  
Polymeric Chain ◽  
Π Interactions ◽  
Intramolecular Hydrogen ◽  
Hydroxy Groups

In the title polymeric comound, [Pb(C7H5O3)2(C14H12N2)] n , the PbII atom is located on a twofold rotation axis and is coordinated by two N atoms from one 2,9-dimethyl-1,10-phenanthroline (dmphen) ligand and six O atoms from four 2-hydroxybenzoate anions. The compound forms a zigzag polymeric chain along the c axis through bridging hydroxy groups of two 2-hydroxybenzoate ligands. The crystal packing is stabilized by the intramolecular hydrogen bonding and π–π interactions between dmphen rings of neighboring molecules, with a distance between the ring planes of 3.385 (3) Å.

Crystal Engineering Studies on Ionic Crystals of Pyridine and Carboxylic Acid Derivatives Containing Amide Functional Groups

2010 ◽  
Vol 63 (4) ◽  
pp. 578 ◽  
Author(s):  
Lalit Rajput ◽  
Ramkinkar Santra ◽  
Kumar Biradha
Keyword(s):  
Crystal Engineering ◽  
Intramolecular Hydrogen Bonding ◽  
Supramolecular Synthon ◽  
Pyromellitic Acid ◽  
Trimesic Acid ◽  
Supramolecular Architectures ◽  
Pyridinium Cations ◽  
Intramolecular Hydrogen ◽  
Hydroxy Groups ◽  
Planar Geometries

Seven crystal structures of pyromellitic acid or trimesic acid salts of molecules that contain pyridine and amide functionalities were determined and their structures were analyzed in detail in terms of various intermolecular interactions. The presence of multiple functionalities (acid, pyridine, amide, and hydroxy groups) in these structures resulted in diversified supramolecular architectures. Amide-to-amide hydrogen bonds are not observed in any of these structures because of interference by the anions, water molecules, or pyridinium cations. The symmetry of the components was found to be important in determining the resultant supramolecular synthon and, therefore, the overall architecture. The pyromellitate anions exhibited four types of geometries which, differ in valencies and intramolecular hydrogen bonding, and these anions also exhibit self stacks when they have planar geometries.

scholarly journals Multicentered hydrogen bonding in 1-[(1-deoxy-β-D-fructopyranos-1-yl)azaniumyl]cyclopentanecarboxylate (`D-fructose-cycloleucine')

2019 ◽  
Vol 75 (8) ◽  
pp. 1096-1101 ◽  
Author(s):  
Valeri V. Mossine ◽  
Charles L. Barnes ◽  
Thomas P. Mawhinney
Keyword(s):  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Side Chain ◽  
Slow Rotation ◽  
H Nmr ◽  
Compound C ◽  
Nmr Data ◽  
Cyclopentane Ring ◽  
Intramolecular Hydrogen ◽  
Hydroxy Groups

The title compound, C12H21NO7, (I), is conformationally unstable; the predominant form present in its solution is the β-pyranose form (74.3%), followed by the β- and α-furanoses (12.1 and 10.2%, respectively), α-pyranose (3.4%), and traces of the acyclic carbohydrate tautomer. In the crystalline state, the carbohydrate part of (I) adopts the 2 C 5 β-pyranose conformation, and the amino acid portion exists as a zwitterion, with the side chain cyclopentane ring assuming the E 9 envelope conformation. All heteroatoms are involved in hydrogen bonding that forms a system of antiparallel infinite chains of fused R 3 3(6) and R 3 3(8) rings. The molecule features extensive intramolecular hydrogen bonding, which is uniquely multicentered and involves the carboxylate, ammonium and carbohydrate hydroxy groups. In contrast, the contribution of intermolecular O...H/H...O contacts to the Hirshfeld surface is relatively low (38.4%), as compared to structures of other D-fructose-amino acids. The 1H NMR data suggest a slow rotation around the C1—C2 bond in (I), indicating that the intramolecular heteroatom contacts survive in aqueous solution of the molecule as well.

Matrix-Isolation Infrared Spectroscopy of Organic Phosphates

1994 ◽  
Vol 48 (1) ◽  
pp. 7-12 ◽  
Author(s):  
Lisa George ◽  
K. Sankaran ◽  
K. S. Viswanathan ◽  
C. K. Mathews
Keyword(s):  
Alkyl Chain ◽  
Matrix Isolation ◽  
Intramolecular Hydrogen Bonding ◽  
Alkyl Chain Length ◽  
Triethyl Phosphate ◽  
Trimethyl Phosphate ◽  
The Matrix ◽  
Intramolecular Hydrogen ◽  
First Time ◽  
Peak Widths

Matrix-isolation infrared spectra of trimethyl phosphate (TMP), triethyl phosphate (TEP), and tri- n-butyl phosphate (TBP), in argon and nitrogen matrices, are reported for the first time. The peak widths of the sharpest features in our matrix-isolated spectra are typically 2 cm−1, compared with peak widths of 40 cm−1 seen in liquids for these compounds. Comparison with the vapor-phase spectrum of TMP reported earlier indicates that TMP is trapped in two different conformations in these matrices. Similar spectra were also obtained for TEP. Our matrix-isolated spectra indicate that the intramolecular hydrogen bonding (which is believed to be responsible for the lowering of the P=O frequency in the C3, conformer relative to the C3 conformer in these compounds) is stronger in TEP than in TMP. In the case of TBP, the peak widths were larger (8–10 cm−1) than those obtained for TMP and TEP. This observation is probably due to a distribution of conformers that may be trapped in the matrix, as a result of the increased alkyl chain length in TBP.

Effects of intramolecular hydrogen bonding on the conformation and luminescence properties of dibenzoylpyridine-based thermally activated delayed fluorescence materials

2019 ◽  
Vol 7 (42) ◽  
pp. 13104-13110 ◽  
Author(s):  
Jayabalan Pandidurai ◽  
Jayachandran Jayakumar ◽  
Natarajan Senthilkumar ◽  
Chien-Hong Cheng
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Linear Chain ◽  
Intramolecular Hydrogen Bonding ◽  
Delayed Fluorescence ◽  
Chain Conformation ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Intramolecular Hydrogen ◽  
First Time

The crystal structures show a U shape for 26DAcBPy and 26DPXZBPy and a linear chain conformation for 25DAcBPy; for the first time, we reveal that the conformations are the result of intramolecular hydrogen bonding of these molecules.

2′-Oxoethyl Flavin Revisited

2008 ◽  
Vol 63 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Jiří Svoboda ◽  
Burkhard König ◽  
Keyarash Sadeghian ◽  
Martin Schützb
Keyword(s):  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Oxidative Degradation ◽  
Nucleophilic Attack ◽  
H Nmr ◽  
Moller Plesset ◽  
Intramolecular Hydrogen ◽  
Hydroxy Groups ◽  
Low Solubility ◽  
Structure Calculations

The present work investigates the possibility of using 2'-oxoethyl flavin (2) as a starting material for the construction of more complicated flavin-based molecules. 2'-Oxoethyl flavin (2), prepared by oxidative degradation of commercially available riboflavin 1, is however a rather untypical aldehyde. It prefers the hydrated gem-diol form 4 in aqueous solution. Ab initio electronic structure calculations, carried out at the level of Møller-Plesset perturbation theory of second order (MP2), predict the existence of an intramolecular hydrogen bond between one of the hydroxy groups of the diol and the N1 atom of the flavin skeleton. This result is supported by 1H NMR measurements which indicate an interaction between the hydroxy groups and the conjugated ring system. We postulate that this rather strong intramolecular hydrogen bond is the origin of the enhanced stability of the gem-diol over the aldehyde form 2. Synthetic applicability of 2'-oxoethyl flavin 2 is limited by low solubility in most organic solvents and sensitivity to basic conditions. The aldehyde functional group is surprisingly reluctant to nucleophilic attack, and several reactions quite typical for aldehydes failed. Nevertheless, reductive amination led to the expected secondary amine 7. Solubility of the molecule thus increased, and a new amino group was introduced.

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