scholarly journals Synthesis and structural reconfirmation of bacillamide B

2015 ◽  
Vol 13 (14) ◽  
pp. 4271-4277 ◽  
Author(s):  
Xue Sun ◽  
Yi Liu ◽  
Jun Liu ◽  
Guofeng Gu ◽  
Yuguo Du
Keyword(s):  
Absolute Configuration ◽  
Optical Rotation ◽  
Specific Optical Rotation ◽  
The Absolute

Synthesis of bacillamide B was accomplished, the absolute configuration was reconfirmed as S, and the specific optical rotation was revised to (−).

Synthesis of anisomycin. Part I. The stereospecific synthesis of N-benzoyl-2-(p-methoxybenzyl)-3-hydroxy-4-carboxamido pyrrolidine and the absolute configuration of anisomycin

1968 ◽  
Vol 46 (7) ◽  
pp. 1101-1104 ◽  
Author(s):  
C. M. Wong
Keyword(s):  
Infrared Spectra ◽  
Absolute Configuration ◽  
Optical Rotation ◽  
Specific Rotation ◽  
Stereospecific Synthesis ◽  
Specific Optical Rotation ◽  
Synthetic Compound ◽  
The Absolute ◽  
Hydrolysis Of ◽  
Absolute Stereochemistry

L-Tyrosine was converted stereospecifically to N-benzoyl-2-(p-methoxybenzyl)-3-hydroxy-4-cyanopyrrolidine (10) which had a specific optical rotation [Formula: see text]. Anisomycin was converted also to N-benzoyl-2-(p-methoxybenzyl)-3-hydroxy-4-cyanopyrrolidine (16) which had a specific rotation [Formula: see text]. The infrared spectra of the synthetic compound and the derivative of anisomycin were superimposable with each other. This result showed that the absolute configuration of the three asymmetric centers in (10) of synthetic origin were 2S, 3S, 4S, and those in (16) were 2R, 3R, 4R. Thus, anisomycin should have the absolute stereochemistry 2R, 3S, 4S as depicted in the structure (2). Hydrolysis of the hydroxy nitriles (8) and (10) gave an identical amide (3) which should have the absolute stereochemistry 2S, 3S, 4R as shown in structure (3).

scholarly journals Absolute Configuration Sensing of Chiral Aryl- and Aryloxy-Propionic Acids by Biphenyl Chiroptical Probes

Chemosensors ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 154
Author(s):  
Stefania Vergura ◽  
Stefano Orlando ◽  
Patrizia Scafato ◽  
Sandra Belviso ◽  
Stefano Superchi
Keyword(s):  
Circular Dichroism ◽  
Absolute Configuration ◽  
Optical Rotation ◽  
Environmental Pollutants ◽  
Red Shift ◽  
Electronic Circular Dichroism ◽  
Configuration Assignment ◽  
Clear Sign ◽  
The Absolute ◽  
Circular Dichroïsm

The absolute configuration of chiral 2-aryl and 2-aryloxy propionic acids, which are among the most common chiral environmental pollutants, has been readily and reliably established by either electronic circular dichroism spectroscopy or optical rotation measurements employing suitably designed 4,4′-disubstituted biphenyl probes. In fact, the 4,4′-biphenyl substitution gives rise to a red shift of the diagnostic electronic circular dichroism signal of the biphenyl A band employed for the configuration assignment, removing its overlap with other interfering dichroic bands and allowing its clear sign identification. The largest A band red shift, and thus the most reliable results, are obtained by employing as a probe the 4,4′-dinitro substituted biphenylazepine 3c. The method was applied to the absolute configuration assignment of 2-arylpropionic acids ibuprofen (1a), naproxen (1b), ketoprofen (1c) and flurbiprofen (1d), as well as to the 2-aryloxypropionic acids 2-phenoxypropionic acid (2a) and 2-naphthoxypropionic acid (2b). This approach, allowing us to reveal the sample’s absolute configuration by simple optical rotation measurements, is potentially applicable to online analyses of both the enantiomeric composition and absolute configuration of these chiral pollutants.

scholarly journals Chiral Resolution and Absolute Configuration of 3α,6β-Dicinnamoyloxytropane and 3α,6β-Di(1-ethyl-1H-pyrrol-2-ylcarbonyloxy)tropane, Constituents of Erythroxylum Species

2014 ◽  
Vol 9 (1) ◽  
pp. 1934578X1400900 ◽  
Author(s):  
Marcelo A. Muñoz ◽  
Solange Arriagada ◽  
Pedro Joseph-Nathan
Keyword(s):  
Stationary Phase ◽  
Natural Product ◽  
Absolute Configuration ◽  
Optical Rotation ◽  
Normal Phase ◽  
Vibrational Circular Dichroism ◽  
Chiral Resolution ◽  
Case Characteristic ◽  
The Absolute

Chiral resolution of (±)-3α,6β-dicinnamoyloxytropane (1) and (±)-3α,6β-di(1-methyl-1 H-pyrrol-2-ylcarbonyloxy)tropane (2), prepared by esterification of (±)-3α,6β-tropanediol (3), was achieved using an amylose-derived HPLC stationary phase and normal phase conditions. The corresponding vibrational circular dichroism (VCD) spectra provided the absolute configuration of the enantiomers as (-)-(3 R,6 R)-1, (+)-(3S,6S)- 1, (-)-(3 R,6 R)-2 and (+)-(3S,6S)- 2. In each case, characteristic VCD bands for the absolute configuration determination of the 3α,6β-tropandiol esters were observed. While the absolute configuration of natural 1, previously isolated from Erythroxylum hypericifolium, could not be established due to the lack of literature optical rotation values, that of catuabine E, previously isolated from E. vacciniifolium, is now assigned as (-)-(3 R,6 R)-2 by comparison with the optical rotation values of the prepared samples and the reported rotation of the natural product.

(3aS,5aR,6R,8aR)-3a-Hydroxy-5a-methyl-6-[(1R,2E,4R)-1,4,5-trimethyl-2-hexen-1-yl]-3a,4,5,5a,6,7,8,8a-octahydro-2H-cyclopenta[e]benzofuran-2-one

2007 ◽  
Vol 63 (11) ◽  
pp. o4196-o4196
Author(s):  
Wen-liang Wang ◽  
Hong-wen Tao ◽  
Wei Sun ◽  
Qian-Qun Gu ◽  
Wei-Ming Zhu
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Absolute Configuration ◽  
Title Compound ◽  
Optical Rotation ◽  
Side Chain ◽  
Compound C ◽  
Extended Chain ◽  
Halotolerant Fungus ◽  
The Absolute

The title compound, C21H32O3, also known as dimethylincisterol A3, was isolated from halotolerant fungus THW-18. It is composed of three fused rings and a side chain. In the crystal structure, the molecules interact with each other via O—H...O hydrogen bonds, resulting in an extended chain along the b axis. The absolute configuration was assigned from the measured optical rotation and reference to the literature.

scholarly journals Absolute Configuration Determination by Quantum Mechanical Calculation of Chiroptical Spectra: Basics and Applications to Fungal Metabolites

2018 ◽  
Vol 25 (2) ◽  
pp. 287-320 ◽  
Author(s):  
Stefano Superchi ◽  
Patrizia Scafato ◽  
Marcin Gorecki ◽  
Gennaro Pescitelli
Keyword(s):  
Natural Products ◽  
Circular Dichroism ◽  
Absolute Configuration ◽  
Optical Rotation ◽  
Computational Approach ◽  
Quantum Mechanical ◽  
Fungal Metabolites ◽  
Common Technique ◽  
The Absolute ◽  
Circular Dichroïsm

Background: Quantum mechanical simulations of chiroptical properties, such as electronic circular dichroism (ECD), optical rotation (OR), and vibrational circular dichroism (VCD), have rapidly become very popular to assign the absolute configuration of novel natural products. Objective: We review the application of the ECD/OR/VCD computational methodology to chiral metabolites of fungal origin. First, we summarize the fundamentals of the three spectroscopies; then, we focus on the specific experimental and computational issues allied to the application of their calculations. Methods: We surveyed the entire literature describing the use of ECD/OR/VCD computations for fungal metabolites, and catalogued all papers according to the method employed and to the structural family of compounds. Then, we chose several examples to illustrate the use of the techniques and highlight the practical application of the computational approach. Results: Our literature survey demonstrates that the simulation of ECD/OR/VCD spectra is nowadays widespread and accessible also to non-experts, although a good computational practice is necessary to avoid wrong assignments. ECD is still the most common technique used in the context of fungal metabolites. OR and VCD may be profitably employed when the compound of interest lacks chromophoric groups. Our examples illustrate that the combination of two or more chiroptical methods is strongly advisable in some cases, especially in the presence of high conformational flexibility, where a single technique does not lead to a safe conclusion. Conclusion: The ECD/OR/VCD computational approach is a reliable and versatile method to assign the absolute configuration of fungal metabolites and related natural products.

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