12 research outputs found
Chirality Switching in Optical Resolution of Mandelic Acid in C1鈥揅4 Alcohols: Elucidation of Solvent Effects Based on X鈥憆ay Crystal Structures of Diastereomeric Salts
Chirality
switching in the optical resolution of mandelic acid
(MA) using (1<i>R</i>,2<i>S</i>)-2-amino-1,2-diphenylethanol
(ADPE) in C1鈥揅4 alcohols is demonstrated herein. Recrystallization
of the diastereomeric mixture of the MA salts from <i>longer</i> alcohol solvents (<i>n</i>-PrOH, <i>s</i>-BuOH, <i>i</i>-BuOH, and <i>n</i>-BuOH) produced the (<i>R</i>)-MA salt, whereas the (<i>S</i>)-MA salt was
preferentially deposited from <i>shorter</i> alcohol solvents
(MeOH, EtOH, <i>i</i>-PrOH, and <i>t</i>-BuOH).
Thermogravimetric analysis and <sup>1</sup>H NMR spectroscopy showed
that all the solvents employed were incorporated in the diastereomeric
salts and the stability of the incorporated alcohols increased with
an increase in the effective surface area of their alkyl chains. The
X-ray crystal structures of the eight solvated diastereomeric salt
pairs revealed that the type of hydrogen-bonding network (sheetlike
or columnar) and the arrangement of the columnar structures were controlled
by the length of the included alcohol. By comparison of the two diastereomeric
MA salt crystal structures, their relative stability to display chirality
switching was investigated
Formation of Ternary Inclusion Crystal and Enantioseparation of Alkyl Aryl Sulfoxides by the Salt of Urea-Modified l鈥慞henylalanine and an Achiral Amine
Chiral
supramolecular hosts comprising urea-modified l-phenylalanines
and achiral primary amines were developed, which facilitated enantioselective
inclusion of alkyl aryl sulfoxides (<b>3</b>) up to 89% ee owing
to the formation of ternary inclusion crystals. From the structural
optimization of the components, the combination of <i>N</i>-(phenylcarbamoyl)-l-phenylalanine (<b>1a</b>) and
benzhydrylamine (<b>2e</b>) showed the best inclusion ability
among the considered supramolecular hosts. The type of the hydrogen-bonding
network of ammonium-carboxylate salts <b>1a</b>路<b>2</b> was dependent on the steric bulk of combined primary amine <b>2</b>. The rigid phenylurea moiety of <b>1a</b> and moderate
steric bulk of <b>2e</b> played an important role in their high
inclusion ability. Host <b>1a</b>路<b>2e</b> afforded
two ternary polymorphic inclusion crystals with the inclusion of acetonitrile.
Furthermore, the crystal structures of <b>1a</b>路<b>2e</b>路<b>3</b> revealed that the inclusion of <b>3</b> was assisted by hydrogen bonding to the host and that stereoselectivity
reversal occurred for larger sulfoxides, which was attributed to packing
variations of one-dimensional hydrogen-bonding networks
Chirality Switching in Optical Resolution of Mandelic Acid in C1鈥揅4 Alcohols: Elucidation of Solvent Effects Based on X鈥憆ay Crystal Structures of Diastereomeric Salts
Chirality
switching in the optical resolution of mandelic acid
(MA) using (1<i>R</i>,2<i>S</i>)-2-amino-1,2-diphenylethanol
(ADPE) in C1鈥揅4 alcohols is demonstrated herein. Recrystallization
of the diastereomeric mixture of the MA salts from <i>longer</i> alcohol solvents (<i>n</i>-PrOH, <i>s</i>-BuOH, <i>i</i>-BuOH, and <i>n</i>-BuOH) produced the (<i>R</i>)-MA salt, whereas the (<i>S</i>)-MA salt was
preferentially deposited from <i>shorter</i> alcohol solvents
(MeOH, EtOH, <i>i</i>-PrOH, and <i>t</i>-BuOH).
Thermogravimetric analysis and <sup>1</sup>H NMR spectroscopy showed
that all the solvents employed were incorporated in the diastereomeric
salts and the stability of the incorporated alcohols increased with
an increase in the effective surface area of their alkyl chains. The
X-ray crystal structures of the eight solvated diastereomeric salt
pairs revealed that the type of hydrogen-bonding network (sheetlike
or columnar) and the arrangement of the columnar structures were controlled
by the length of the included alcohol. By comparison of the two diastereomeric
MA salt crystal structures, their relative stability to display chirality
switching was investigated
Solvent-Induced Reversed Stereoselectivity in Reciprocal Resolutions of Mandelic Acid and <i>erythro</i>-2-Amino-1,2-diphenylethanol
Solvent-induced
chirality switching in reciprocal optical resolution
between mandelic acid (<b>1</b>) and <i>erythro</i>-2-amino-1,2-diphenylethanol (<b>2</b>) has been demonstrated.
The stereochemistry of the deposited salts was controlled by changing
the crystallization solvent from 1-PrOH or 1-BuOH to 1,4-dioxane.
It was revealed from <sup>1</sup>H NMR spectra, thermogravimetric
analysis, and X-ray crystallography of the salts that an equimolar
amount of the crystallization solvent was incorporated in each diastereomeric
salt. On the basis of the crystal structures, it was found that both
the hydrogen-bonding ability and the size of the solvent molecule
played an important role. Differences in the formed hydrogen-bonding
networks (columnar or sheetlike structure) and their packing manner
were found to be crucial for the reversed stereoselectivity. Furthermore,
pseudopolymorphic salt crystals that incorporated 1,4-dioxane were
obtained during the enantioseparation of racemic <b>2</b>, and
their solid-state properties were examined by measurement of their
IR spectra. This solvent-induced dual stereocontrol technique was
successfully applied to the successive resolution process, eliminating
the need to change the resolving agent for access to both enantiomers
of <b>1</b> and <b>2</b>
Solvent-Induced Reversed Stereoselectivity in Reciprocal Resolutions of Mandelic Acid and <i>erythro</i>-2-Amino-1,2-diphenylethanol
Solvent-induced
chirality switching in reciprocal optical resolution
between mandelic acid (<b>1</b>) and <i>erythro</i>-2-amino-1,2-diphenylethanol (<b>2</b>) has been demonstrated.
The stereochemistry of the deposited salts was controlled by changing
the crystallization solvent from 1-PrOH or 1-BuOH to 1,4-dioxane.
It was revealed from <sup>1</sup>H NMR spectra, thermogravimetric
analysis, and X-ray crystallography of the salts that an equimolar
amount of the crystallization solvent was incorporated in each diastereomeric
salt. On the basis of the crystal structures, it was found that both
the hydrogen-bonding ability and the size of the solvent molecule
played an important role. Differences in the formed hydrogen-bonding
networks (columnar or sheetlike structure) and their packing manner
were found to be crucial for the reversed stereoselectivity. Furthermore,
pseudopolymorphic salt crystals that incorporated 1,4-dioxane were
obtained during the enantioseparation of racemic <b>2</b>, and
their solid-state properties were examined by measurement of their
IR spectra. This solvent-induced dual stereocontrol technique was
successfully applied to the successive resolution process, eliminating
the need to change the resolving agent for access to both enantiomers
of <b>1</b> and <b>2</b>
Solvent-Induced Reversed Stereoselectivity in Reciprocal Resolutions of Mandelic Acid and <i>erythro</i>-2-Amino-1,2-diphenylethanol
Solvent-induced
chirality switching in reciprocal optical resolution
between mandelic acid (<b>1</b>) and <i>erythro</i>-2-amino-1,2-diphenylethanol (<b>2</b>) has been demonstrated.
The stereochemistry of the deposited salts was controlled by changing
the crystallization solvent from 1-PrOH or 1-BuOH to 1,4-dioxane.
It was revealed from <sup>1</sup>H NMR spectra, thermogravimetric
analysis, and X-ray crystallography of the salts that an equimolar
amount of the crystallization solvent was incorporated in each diastereomeric
salt. On the basis of the crystal structures, it was found that both
the hydrogen-bonding ability and the size of the solvent molecule
played an important role. Differences in the formed hydrogen-bonding
networks (columnar or sheetlike structure) and their packing manner
were found to be crucial for the reversed stereoselectivity. Furthermore,
pseudopolymorphic salt crystals that incorporated 1,4-dioxane were
obtained during the enantioseparation of racemic <b>2</b>, and
their solid-state properties were examined by measurement of their
IR spectra. This solvent-induced dual stereocontrol technique was
successfully applied to the successive resolution process, eliminating
the need to change the resolving agent for access to both enantiomers
of <b>1</b> and <b>2</b>
Solvent-Induced Reversed Stereoselectivity in Reciprocal Resolutions of Mandelic Acid and <i>erythro</i>-2-Amino-1,2-diphenylethanol
Solvent-induced
chirality switching in reciprocal optical resolution
between mandelic acid (<b>1</b>) and <i>erythro</i>-2-amino-1,2-diphenylethanol (<b>2</b>) has been demonstrated.
The stereochemistry of the deposited salts was controlled by changing
the crystallization solvent from 1-PrOH or 1-BuOH to 1,4-dioxane.
It was revealed from <sup>1</sup>H NMR spectra, thermogravimetric
analysis, and X-ray crystallography of the salts that an equimolar
amount of the crystallization solvent was incorporated in each diastereomeric
salt. On the basis of the crystal structures, it was found that both
the hydrogen-bonding ability and the size of the solvent molecule
played an important role. Differences in the formed hydrogen-bonding
networks (columnar or sheetlike structure) and their packing manner
were found to be crucial for the reversed stereoselectivity. Furthermore,
pseudopolymorphic salt crystals that incorporated 1,4-dioxane were
obtained during the enantioseparation of racemic <b>2</b>, and
their solid-state properties were examined by measurement of their
IR spectra. This solvent-induced dual stereocontrol technique was
successfully applied to the successive resolution process, eliminating
the need to change the resolving agent for access to both enantiomers
of <b>1</b> and <b>2</b>
Solvent-Induced Reversed Stereoselectivity in Reciprocal Resolutions of Mandelic Acid and <i>erythro</i>-2-Amino-1,2-diphenylethanol
Solvent-induced
chirality switching in reciprocal optical resolution
between mandelic acid (<b>1</b>) and <i>erythro</i>-2-amino-1,2-diphenylethanol (<b>2</b>) has been demonstrated.
The stereochemistry of the deposited salts was controlled by changing
the crystallization solvent from 1-PrOH or 1-BuOH to 1,4-dioxane.
It was revealed from <sup>1</sup>H NMR spectra, thermogravimetric
analysis, and X-ray crystallography of the salts that an equimolar
amount of the crystallization solvent was incorporated in each diastereomeric
salt. On the basis of the crystal structures, it was found that both
the hydrogen-bonding ability and the size of the solvent molecule
played an important role. Differences in the formed hydrogen-bonding
networks (columnar or sheetlike structure) and their packing manner
were found to be crucial for the reversed stereoselectivity. Furthermore,
pseudopolymorphic salt crystals that incorporated 1,4-dioxane were
obtained during the enantioseparation of racemic <b>2</b>, and
their solid-state properties were examined by measurement of their
IR spectra. This solvent-induced dual stereocontrol technique was
successfully applied to the successive resolution process, eliminating
the need to change the resolving agent for access to both enantiomers
of <b>1</b> and <b>2</b>
Solvent-Induced Reversed Stereoselectivity in Reciprocal Resolutions of Mandelic Acid and <i>erythro</i>-2-Amino-1,2-diphenylethanol
Solvent-induced
chirality switching in reciprocal optical resolution
between mandelic acid (<b>1</b>) and <i>erythro</i>-2-amino-1,2-diphenylethanol (<b>2</b>) has been demonstrated.
The stereochemistry of the deposited salts was controlled by changing
the crystallization solvent from 1-PrOH or 1-BuOH to 1,4-dioxane.
It was revealed from <sup>1</sup>H NMR spectra, thermogravimetric
analysis, and X-ray crystallography of the salts that an equimolar
amount of the crystallization solvent was incorporated in each diastereomeric
salt. On the basis of the crystal structures, it was found that both
the hydrogen-bonding ability and the size of the solvent molecule
played an important role. Differences in the formed hydrogen-bonding
networks (columnar or sheetlike structure) and their packing manner
were found to be crucial for the reversed stereoselectivity. Furthermore,
pseudopolymorphic salt crystals that incorporated 1,4-dioxane were
obtained during the enantioseparation of racemic <b>2</b>, and
their solid-state properties were examined by measurement of their
IR spectra. This solvent-induced dual stereocontrol technique was
successfully applied to the successive resolution process, eliminating
the need to change the resolving agent for access to both enantiomers
of <b>1</b> and <b>2</b>
Solvent-Induced Reversed Stereoselectivity in Reciprocal Resolutions of Mandelic Acid and <i>erythro</i>-2-Amino-1,2-diphenylethanol
Solvent-induced
chirality switching in reciprocal optical resolution
between mandelic acid (<b>1</b>) and <i>erythro</i>-2-amino-1,2-diphenylethanol (<b>2</b>) has been demonstrated.
The stereochemistry of the deposited salts was controlled by changing
the crystallization solvent from 1-PrOH or 1-BuOH to 1,4-dioxane.
It was revealed from <sup>1</sup>H NMR spectra, thermogravimetric
analysis, and X-ray crystallography of the salts that an equimolar
amount of the crystallization solvent was incorporated in each diastereomeric
salt. On the basis of the crystal structures, it was found that both
the hydrogen-bonding ability and the size of the solvent molecule
played an important role. Differences in the formed hydrogen-bonding
networks (columnar or sheetlike structure) and their packing manner
were found to be crucial for the reversed stereoselectivity. Furthermore,
pseudopolymorphic salt crystals that incorporated 1,4-dioxane were
obtained during the enantioseparation of racemic <b>2</b>, and
their solid-state properties were examined by measurement of their
IR spectra. This solvent-induced dual stereocontrol technique was
successfully applied to the successive resolution process, eliminating
the need to change the resolving agent for access to both enantiomers
of <b>1</b> and <b>2</b>