5 research outputs found
A Foldable Cyclic Oligomer: Chiroptical Modulation through Molecular Folding upon Complexation and a Change in Temperature
A foldable
cyclic oligomer <b>1</b> consisting of three terephthalamide
units spaced with a 3-fold <i>o</i>-phenylene unit presented
a dynamic pair of enantiomeric forms through molecular folding, to
which the external chirality on a ditopic guest [(<i>S</i>,<i>S</i>)-<b>2</b> or (<i>R</i>,<i>R</i>)-<b>2</b>] was supramolecularly transferred to prefer
a particular sense of dynamic helicity [(<i>M</i>,<i>M</i>)-/(<i>P</i>,<i>P</i>)-<b>1</b> and (<i>M</i>,<i>M</i>,<i>P</i>)-/(<i>P</i>,<i>P</i>,<i>M</i>)-<b>1</b>].
In the macrocycle, the terephthalamide units acted as exotopic binding
sites to fold into helical forms upon complexation. The internal chirality
associated with a host [(<i>R</i>,<i>R</i>,<i>R</i>,<i>R</i>,<i>R</i>,<i>R</i>)-<b>1b</b>] had no preference in a helical sense in the absence
of a guest. Instead, the internal chirality was responsible for the
signal modulation that it was cooperatively or competitively transferred
in response to the external chirality on a guest (<i>S</i>,<i>S</i>)-<b>2</b> or (<i>R</i>,<i>R</i>)-<b>2</b>. During the diastereomeric complexation,
a particular sense of dynamic helicity was favored due to cooperative
transmission of chirality when the helical preference was matched
between the host and guest. Alternatively, the host complexed with
an antipodal guest underwent a drastic change in conformation upon
a change in temperature
Dynamic Figure Eight Chirality: Multifarious Inversions of a Helical Preference Induced by Complexation
We demonstrate two types of inversion
of a helical preference upon
the 1:1 complexation of a dynamic figure eight molecule with a guest
molecule through the controlled transmission of point chirality. We
designed a series of macrocycles that prefer a nonplanar conformation
with figure eight chirality. These macrocycles are composed of a chirality-transferring
unit (terephthalamide) and a structure-modifying unit (two <i>o</i>-phenylene rings spaced with a varying number of triple
bonds). The former unit provides a binding site for capturing a guest
molecule through the formation of hydrogen bonds. The attachment of
chiral auxiliaries to the former unit induces a helical preference
for a particular sense through the intramolecular transmission of
point chirality. For relatively small-sized macrocycles, the preferred
sense was reversed upon complexation with an achiral guest. Contrary
preferences before and after complexation were both seen for chiral
auxiliaries associated with a figure eight host through two-way intramolecular
transmission of the single chiral source. Alternatively, the helical
preference induced in relatively large-sized macrocycles was reversed
only when a figure eight host formed a 1:1 complex with a particular
enantiomeric guest through the supramolecular transmission of point
chirality in the guest. This stereospecific inversion of a helical
preference is rare
Dynamic Figure Eight Chirality: Multifarious Inversions of a Helical Preference Induced by Complexation
We demonstrate two types of inversion
of a helical preference upon
the 1:1 complexation of a dynamic figure eight molecule with a guest
molecule through the controlled transmission of point chirality. We
designed a series of macrocycles that prefer a nonplanar conformation
with figure eight chirality. These macrocycles are composed of a chirality-transferring
unit (terephthalamide) and a structure-modifying unit (two <i>o</i>-phenylene rings spaced with a varying number of triple
bonds). The former unit provides a binding site for capturing a guest
molecule through the formation of hydrogen bonds. The attachment of
chiral auxiliaries to the former unit induces a helical preference
for a particular sense through the intramolecular transmission of
point chirality. For relatively small-sized macrocycles, the preferred
sense was reversed upon complexation with an achiral guest. Contrary
preferences before and after complexation were both seen for chiral
auxiliaries associated with a figure eight host through two-way intramolecular
transmission of the single chiral source. Alternatively, the helical
preference induced in relatively large-sized macrocycles was reversed
only when a figure eight host formed a 1:1 complex with a particular
enantiomeric guest through the supramolecular transmission of point
chirality in the guest. This stereospecific inversion of a helical
preference is rare
Dynamic Figure Eight Chirality: Multifarious Inversions of a Helical Preference Induced by Complexation
We demonstrate two types of inversion
of a helical preference upon
the 1:1 complexation of a dynamic figure eight molecule with a guest
molecule through the controlled transmission of point chirality. We
designed a series of macrocycles that prefer a nonplanar conformation
with figure eight chirality. These macrocycles are composed of a chirality-transferring
unit (terephthalamide) and a structure-modifying unit (two <i>o</i>-phenylene rings spaced with a varying number of triple
bonds). The former unit provides a binding site for capturing a guest
molecule through the formation of hydrogen bonds. The attachment of
chiral auxiliaries to the former unit induces a helical preference
for a particular sense through the intramolecular transmission of
point chirality. For relatively small-sized macrocycles, the preferred
sense was reversed upon complexation with an achiral guest. Contrary
preferences before and after complexation were both seen for chiral
auxiliaries associated with a figure eight host through two-way intramolecular
transmission of the single chiral source. Alternatively, the helical
preference induced in relatively large-sized macrocycles was reversed
only when a figure eight host formed a 1:1 complex with a particular
enantiomeric guest through the supramolecular transmission of point
chirality in the guest. This stereospecific inversion of a helical
preference is rare
Total Synthesis of Thelephantin O, Vialinin A/Terrestrin A, and Terrestrins B–D
The first total synthesis of natural, unsymmetrical 2′,3′-diacyloxy-<i>p</i>-terphenyls, thelephantin O (<b>1</b>) and terrestrins
C and D (<b>2</b> and <b>3</b>, respectively), was achieved
via a practical route which was also applicable to the synthesis of
the symmetrical diesters vialinin A/terrestrin A (<b>4</b>)
and terrestrin B (<b>5</b>). Compounds <b>1</b>–<b>5</b> exhibited cytotoxicity against cancer cells (HepG2 and Caco2)
with IC<sub>50</sub> values of 13.6–26.7 μmol/L