Absolute configurations and CD spectra of axially chiral biphenyls prepared in a facile manner by crystallization-induced configuration transformation

Chirality ◽  
2010 ◽  
pp. n/a-n/a ◽  
Author(s):  
Limin Wang ◽  
Senxiang Cheng ◽  
Rongfeng Chen ◽  
Junbiao Chang
Keyword(s):  
Cd Spectra ◽  
Axially Chiral

Total Synthesis of Axially-Chiral Cannabinols: A New Platform for Cannabinoid-Based Drug Discovery

2019 ◽  
Author(s):  
Primali Navaratne ◽  
Jenny Wilkerson ◽  
Kavindri Ranasinghe ◽  
Evgeniya Semenova ◽  
Lance McMahon ◽  
...  
Keyword(s):  
Drug Discovery ◽  
Total Synthesis ◽  
Ground State ◽  
Chemical Space ◽  
Modern Medicine ◽  
The Novel ◽  
Pharmaceutical Development ◽  
Bioactive Component ◽  
Axially Chiral ◽  
New Directions

<div> <div> <div> <p>Phytocannabinoids, molecules isolated from cannabis, are gaining attention as promising leads in modern medicine, including pain management. Considering the urgent need for combating the opioid crisis, new directions for the design of cannabinoid-inspired analgesics are of immediate interest. In this regard, we have hypothesized that axially-chiral-cannabinols (ax-CBNs), unnatural (and unknown) isomers of cannabinol (CBN) may be valuable scaffolds for cannabinoid-inspired drug discovery. There are multiple reasons for thinking this: (a) ax-CBNs would have ground-state three-dimensionality akin to THC, a key bioactive component of cannabis, (b) ax-CBNs at their core structure are biaryl molecules, generally attractive platforms for pharmaceutical development due to their ease of functionalization and stability, and (c) atropisomerism with respect to phytocannabinoids is unexplored “chemical space.” Herein we report a scalable total synthesis of ax-CBNs, examine physical properties experimentally and computationally, and provide preliminary behavioral and analgesic analysis of the novel scaffolds. </p> </div> </div> </div>

Synthesis of Axially Chiral 2,2’-Bisphosphobiarenes via a Nickel-Catalyzed Asymmetric Ullmann Coupling: General Access to Privileged Chiral Ligands without Optical Resolution

2020 ◽  
Author(s):  
Ziqing Zuo ◽  
Raphael Kim ◽  
Donald Watson
Keyword(s):  
Optical Resolution ◽  
Chiral Ligands ◽  
Chiral Auxiliaries ◽  
Axially Chiral ◽  
Ullmann Coupling

<div><p>We report an asymmetric Ullmann-type homocoupling of <i>ortho-</i>(iodo)arylphosphine oxides and <i>ortho</i>-(iodo)arylphosphonates that results in highly enantioenriched axially chiral bisphosphine oxides and bisphosphonates in good yields and excellent enantioselectivities. These products are readily converted to enantioenriched biaryl bisphosphines without need for chiral auxiliaries or optical resolution. This process provides a straightforward and practical route for the development of previously uninvestigated atroposelective biaryl bisphosphine ligands.</p></div>

A New Interpretation of the Structure and Solvent Dependence of the Far UV Circular Dichroism Spectrum of Short Oligopeptides

2019 ◽  
Author(s):  
Anshuman Kumar ◽  
Reinhard Schweitzer-Stenner ◽  
Bryan Wong
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Cd Spectra ◽  
Functional Theory ◽  
Polyproline Ii ◽  
Solvent Dependence ◽  
Explicit Consideration ◽  
New Interpretation ◽  
Implicit And Explicit ◽  
Explicit Water

In this work, we carry out new time-dependent density functional theory calculations on the cationic tripeptide GAG in implicit and explicit water to determine the transitions that give rise to the observed CD signals of polyproline II and β-strand conformations. Our results reveal a plethora of electronic transitions that are governed by configurational interactions between multiple molecular orbital transitions of comparable energy. We also show that reproducing the CD spectra of polyproline II and β-strand conformations requires the explicit consideration of water molecules. The structure dependence of delocalized occupied orbitals contributes to the experimentally-observed invalidation of Flory’s isolated pair hypothesis.

A New Interpretation of the Structure and Solvent Dependence of the Far UV Circular Dichroism Spectrum of Short Oligopeptides

2019 ◽  
Author(s):  
Anshuman Kumar ◽  
Reinhard Schweitzer-Stenner ◽  
Bryan Wong
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Cd Spectra ◽  
Functional Theory ◽  
Polyproline Ii ◽  
Solvent Dependence ◽  
Explicit Consideration ◽  
New Interpretation ◽  
Implicit And Explicit ◽  
Explicit Water

In this work, we carry out new time-dependent density functional theory calculations on the cationic tripeptide GAG in implicit and explicit water to determine the transitions that give rise to the observed CD signals of polyproline II and β-strand conformations. Our results reveal a plethora of electronic transitions that are governed by configurational interactions between multiple molecular orbital transitions of comparable energy. We also show that reproducing the CD spectra of polyproline II and β-strand conformations requires the explicit consideration of water molecules. The structure dependence of delocalized occupied orbitals contributes to the experimentally-observed invalidation of Flory’s isolated pair hypothesis.

Effect of polymerization degree of oligogalacturonates and D-galacturonans on their circular dichroic spectra

1979 ◽  
Vol 44 (1) ◽  
pp. 167-173 ◽  
Author(s):  
Slavomír Bystrický ◽  
Rudolf Kohn ◽  
Tibor Sticzay
Keyword(s):  
Physicochemical Properties ◽  
Aqueous Solutions ◽  
Helical Structure ◽  
Monomeric Unit ◽  
Polymerization Degree ◽  
Cd Spectra ◽  
Circular Dichroic

The CD spectra of aqueous solutions of homopolymeric sodium oligogalacturonates and D-galacturonans of polymerization degree n = 1-64, as well as lower calcium oligogalacturonates (n = 1-5) were measured. Chiroptic properties were correlated with the polymerization degree in terms of optical superposition of monomeric unit increments. Interpretation of obtained data, respecting further physicochemical properties entitles to conclude that the conformation of macromolecules of D-galacturonan in solution is close to helical structure.

Series of sequential polypeptides containing lysine or arginine: Preparation and characterization

1988 ◽  
Vol 53 (1) ◽  
pp. 145-156 ◽  
Author(s):  
Jana Pírková ◽  
Svetlana Churkina ◽  
Vladimír Gut ◽  
Ivo Frič ◽  
Karel Bláha
Keyword(s):  
Molecular Weight ◽  
Amino Acid ◽  
Peptide Synthesis ◽  
Average Molecular Weight ◽  
Basic Amino Acid ◽  
Cd Spectra ◽  
Active Esters ◽  
Marked Tendency

The sequential polypeptides (Lys-Ala)n, (Lys-Ala-Ala)n, (Lys-Ala-Ala-Ala)n, (Lys-Leu-Ala)n, (Lys-Leu-Ala-Ala)n, (Lys-Leu-Ala-Ala-Ala)n, (Lys-Ala-Leu)n, (Lys-Ala-Leu-Ala)n, (Orn-Leu-Ala)n,(Arg-Ala-Ala)n, (Arg-Leu-Ala)n, (Arg-Leu-Ala-Ala)n, (Arg-Ala-Leu)n, and (Arg-Ala-Leu-Ala)n were synthesized by polymerization of active esters (1-succinimidyl or pentafluorophenyl) of the corresponding Nα-deblocked monomers. The monomers were prepared using the usual methods of peptide synthesis in solution. Upon dialysis, the average molecular weight of the polymer was 6 000-9 000 as determined by sedimentation in ultracentrifuge. Polypeptides, containing leucine in addition to the basic amino acid, showed a marked tendency to aggregation. CD spectra of the products were measured for characterization.

Conformation of ring A in 3-oxotriterpenoids. Dipole moments and CD spectra

1986 ◽  
Vol 51 (3) ◽  
pp. 611-620 ◽  
Author(s):  
Jiří Klinot ◽  
Václav Všetečka ◽  
Eva Klinotová ◽  
Alois Vystrčil
Keyword(s):  
Dipole Moments ◽  
Cd Spectra ◽  
Boat Form ◽  
Methyl Derivatives

The A ring of 3-oxotriterpenoids allobetulone (I) and 3-xo-lupane-28-nitrile (IV) exists by about 40% in the boat form as derived from comparison of their dipole moments with those of 2α-methyl derivatives II, V (chair models) and 2β-methyl compounds III, VI (boat models). The same result was obtained from the CD spectra of 3-oxotriterpenoids I-VIII and from isomerization of the 2α- and 2β-substituted ketones XI and XII, respectively.

Synthesis and conformation of sequential basic polypeptides with branched and linear side chains

1985 ◽  
Vol 50 (12) ◽  
pp. 2925-2936 ◽  
Author(s):  
Štěpánka Štokrová ◽  
Jan Pospíšek ◽  
Jaroslav Šponar ◽  
Karel Bláha
Keyword(s):  
Amino Acid ◽  
Salt Concentration ◽  
Salt Solution ◽  
Theoretical Work ◽  
Side Chain ◽  
Amino Acid Residues ◽  
Cd Spectra ◽  
Low Salt ◽  
Conformational Freedom ◽  
Basic Polypeptides

Polypeptides (Lys-X-Ala)n and (Lys-X-Gly)n in which X represents residues of isoleucine and norleucine, respectively, and polypeptide (Tle-Lys-Ala)n, were synthesized via polymerization of 1-hydroxysuccinimidyl esters of the appropriate tripeptides to complete previously studied series. Circular dichroism (CD) spectra of the respective polymers were measured as a function of pH and salt concentration of the medium. The results were correlated with those obtained previously with the same series containing different amino acid residues at the X-position. The helix forming ability of the polypeptides (Lys-X-Ala)n with linear X side chain was found to be independent of the length. In the series (Lys-X-Gly)n the unordered conformation was the most probable one except (Lys-Ile-Gly)n. This polymer assumed the β conformation even in low salt solution at neutral pH. An agreement with some theoretical work concerned with the restriction of conformational freedom of amino acid residue branching at Cβ atom with our experimental results is evident.

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