scholarly journals Solvent-assisted monomeric molecular structure of the phosphate diester and the synthesis of menthol-based phosphate diesters

2019 ◽  
Vol 131 (12) ◽  
Author(s):  
Debdeep Mandal ◽  
Vivek Gupta ◽  
Biswajit Santra ◽  
Nicolas Chrysochos ◽  
Vivek W Bhoyare ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Phosphate Diester ◽  
Phosphate Diesters

Acceleration of the methanolysis of phosphate diesters promoted by La(OTf)3 — The analysis of non-integer pH/rate profiles resulting from changes in metal ion speciation

2005 ◽  
Vol 83 (9) ◽  
pp. 1268-1276 ◽  
Author(s):  
Graham TT Gibson ◽  
Alexei A Neverov ◽  
Allen Chun-Tien Teng ◽  
R S Brown
Keyword(s):  
Kinetic Data ◽  
Metal Ion ◽  
General Observation ◽  
Transient Complex ◽  
Phosphate Diester ◽  
Nitrophenyl Phosphate ◽  
Speciation Diagrams ◽  
Diphenyl Phosphate ◽  
The Individual ◽  
Phosphate Diesters

In a previous publication (A.A. Neverov and R.S. Brown. Inorg. Chem. 40, 3588 (2001)) we reported very effective catalysis of the methanolysis of some phosphate diesters (methyl p-nitrophenyl phosphate (1), bis(p-nitrophenyl) phosphate (2), and diphenyl phosphate (3)) promoted by La3+, and noted a general observation that the plots of logkcat vs. [Formula: see text]pH had non-integer gradients. In this report the origins of that behaviour are studied and analyzed through determination of the speciation of La3+(–OCH3)n, (La3+)2(–OCH3)m, (La3+)2:phosphate:(–OCH3)y forms in solution as a function of [Formula: see text]pH. Potentiometric titrations of solutions of La(OTf)3 in methanol at low (<1 × 10–4 mol/L) and high (>1 × 10–3 mol/L) concentration were analyzed through fits of the data to various models to provide speciation diagrams of the various La3+ forms in the absence of phosphate. Titrations of La3+ in the presence of diphenyl phosphate were also analyzed to provide speciation diagrams for phosphate bound forms. The kinetic data for the La3+ catalyzed methanolysis of 1 were analyzed through fitting the kinetic data at low and high [La3+] as a function of [Formula: see text]pH to a linear combination of the individual kinetic contributions of each species. Overall the data are best analyzed in the low [La3+] domain as resulting from methoxide attack on a transient complex of phosphate bound to La3+(–OCH3)0,1. In the high [La3+] domain the data fit two kinetically equivalent processes involving either a spontaneous decomposition of (La3+)2:1–:(–OCH3)2,3,4,5 or external methoxide attack on (La3+)2:1–:(–OCH3)1,2,3,4. Key words: lanthanides, phosphate diester, methanolysis, kinetics, speciation, metal ion catalysis of methanolysis, DNA model methanolysis.

scholarly journals Comparative Study of Bis(Benzyl)Phosphate Triesters of 2′,3′-Dideoxy-2′,3′-Didehydrothymidine (d4T) and CycloSal-d4TMP — Hydrolysis, Mechanistic Insights and Anti-HIV Activity

2002 ◽  
Vol 13 (2) ◽  
pp. 101-114 ◽  
Author(s):  
Chris Meier ◽  
Ulrike Muus ◽  
Jürgen Renze ◽  
Lieve Naesens ◽  
Erik De Clercq ◽  
...  
Keyword(s):  
Comparative Study ◽  
Cell Extract ◽  
Degradation Pathway ◽  
Phenyl Phosphate ◽  
Phosphate Diester ◽  
Chemical Hydrolysis ◽  
The Difference ◽  
Phosphate Diesters ◽  
Selective Formation ◽  
Anti Hiv

A comparative study of three cycloSal-d4TMP 1, 2 and 3 and a variety of bis(benzyl) phosphate triester 4–8 of the antivirally active nucleoside analogue 2′,3′-dideoxy-2′,3′-didehydrothymidine (d4T) will be described. This study has been initiated by the observation that the introduction of a simple 7-methyl group in the cycloSal-structure (2) led to a completely different hydrolysis pattern as compared to the prototype cycloSal- d4TMP 1. Instead of the selective formation of d4TMP, a phenyl phosphate diester was formed in the case of the 7-methyl-substituted compound 2. The difference in degradation pathway was caused by a change of the reaction mechanism. The phenyl phosphate diester was chemically and enzymatically inert to further cleavage to yield d4TMP. For comparison bis(benzyl)-d4TMP 4, bis(α-methylbenzyl)-d4TMP 5, bis(α-methoxycarbonylmethyl [MCM]-benzyl)-d4TMP 6 as well as the enzyme-cleavable bis(4-acetoxybenzyl)- d4TMP [bis(AB)-d4TMP(7 and bis(α-methoxycarbonylmethyl-4-acetoxybenzyl)-d4TMP [bis(α-MCM-AB)-d4TMP] 8 were synthesized. Chemical hydrolysis studies proved that all bis(benzyl) triesters hydrolyze to give the intermediate benzyl phosphate diesters. Moreover, the latter two triesters 7,8 and cycloSal-d4TMPs 1 and 3 led finally to the delivery of d4TMP. The chemical hydrolysis studies allowed a detailed mechanistic interpretation of the degradation pathways of triesters 1–8. Cell extract studies of the bis(benzyl) triesters 4–8 confirmed that only triesters 7 and 8 released d4TMP although with a considerable increase of the reaction rate. Anti-HIV evaluation of the compounds showed that cycloSal-d4TMP 1 and the bis(AB) triesters 7,8 were entirely independent of the presence of cellular thymidine kinase (TK).

2′-O-Methyl-cis-adenosine 3′,5′-cyclic methyl monophosphate, a new model system for cAMP. Aspects of structure and reactivity

1993 ◽  
Vol 71 (6) ◽  
pp. 855-863 ◽  
Author(s):  
Niek L.H.L. Broeders ◽  
Arthur P. van der Heiden ◽  
Leo H. Koole ◽  
Jan A. Kanters ◽  
Arie Schouten
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Orthorhombic Space Group ◽  
H Nmr ◽  
Phosphate Diester ◽  
Phosphate Diesters ◽  
Hydrolysis Of ◽  
Adenine Base

This study is focussed on 2′-O-methyl-cis-adenosine 3′,5′-cyclic methyl monophosphate (cis-4; cis describes the relationship between OMe (bound to phosphorus) and the adenine base), which is regarded a model for enzyme-bound cyclic adenosine monophosphate (cAMP). In this complex the negative phosphate charge is shielded in part via complexation with cationic sites on the enzyme surface. We report synthesis, crystal structure, solution conformation (400 MHz 1H NMR), and kinetic-mechanistic aspects of the alkaline hydrolysis of cis-4. The methanol solvate of cis-4 crystallizes in the orthorhombic space group P212121 and the cell dimensions are a = 8.170(2) Å, b = 9.249(1) Å, c = 23.699(4) Å; V = 1788.5(6) Å3; Z = 4 molecules per cell. Least-squares refinement converged at R = 0.062 for 2006 observed reflections. The adenine bases are linked via [Formula: see text] and [Formula: see text] hydrogen bonds in such a way that infinite one-dimensional chains are formed. This hydrogen bond scheme is very similar to that observed in the structure of 2′-deoxy-3′,5′-di-O-acetyl adenosine. An additional hydrogen bond is formed between methanol, incorporated in the crystal structure, and the adenine base. The conformational preferences of the cis-4 dissolved in methanol have been determined with 400 MHz 1H NMR. It is found that the conformations observed in the solid and solution states are practically the same. Hydrolysis of the title compound yields two acyclic phosphate diesters (a 3′- and a 5′-phosphate diester). The intermediates formed during the hydrolysis reaction are most likely five-coordinated phosphorus (PV) compounds with a trigonal bipyramidal geometry and an equatorial-axial located 3′,5′-dioxaphosphorinane ring.

Molecular Structure of the Outermost Cell Wall Component of Spirillum Serpens

1977 ◽  
Vol 35 ◽  
pp. 342-343
Author(s):  
Wah Chiu ◽  
David Grano
Keyword(s):  
Molecular Structure ◽  
Cell Wall ◽  
Outer Membrane ◽  
Gel Electrophoresis ◽  
Electron Microscopic Examination ◽  
Electron Microscopic ◽  
Cell Wall Component ◽  
Protein Components ◽  
Exposure Technique ◽  
Structural Aspects

The periodic structure external to the outer membrane of Spirillum serpens VHA has been isolated by similar procedures to those used by Buckmire and Murray (1). From SDS gel electrophoresis, we have found that the isolated fragments contain several protein components, and that the crystalline structure is composed of a glycoprotein component with a molecular weight of ∽ 140,000 daltons (2). Under an electron microscopic examination, we have visualized the hexagonally-packed glycoprotein subunits, as well as the bilayer profile of the outer membrane. In this paper, we will discuss some structural aspects of the crystalline glycoproteins, based on computer-reconstructed images of the external cell wall fragments.The specimens were prepared for electron microscopy in two ways: negatively stained with 1% PTA, and maintained in a frozen-hydrated state (3). The micrographs were taken with a JEM-100B electron microscope with a field emission gun. The minimum exposure technique was essential for imaging the frozen- hydrated specimens.

On the relation between isotope effects on vapour pressure and molecular structure

1963 ◽  
Vol 60 ◽  
pp. 52-55
Author(s):  
István Kiss ◽  
Lajos Matus ◽  
István Opauszky
Keyword(s):  
Molecular Structure ◽  
Vapour Pressure ◽  
Isotope Effects
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