The Journal of Organic Chemistry,
Journal Year:
2022,
Volume and Issue:
87(6), P. 4154 - 4167
Published: March 3, 2022
The
reaction
of
a
series
anomeric
thioglycosides
with
various
glycosyl
acceptors
and
N-iodosuccinimide/catalytic
triflic
acid
was
investigated
respect
to
reactivity
selectivity.
In
general,
β-configured
donors
were
found
give
more
β-selective
outcome
compared
their
α-configured
counterparts.
relative
measured
through
competition
experiments,
the
following
order
established:
phenyl,
tolyl,
methyl,
ethyl,
isopropyl,
1-adamantyl.
Journal of the American Chemical Society,
Journal Year:
2022,
Volume and Issue:
144(44), P. 20258 - 20266
Published: Oct. 27, 2022
The
stereoselective
formation
of
1,2-cis-glycosidic
bonds
is
a
major
bottleneck
in
the
synthesis
carbohydrates.
We
here
investigate
how
electron
density
acyl
protecting
groups
influences
stereoselectivity
by
fine-tuning
efficiency
remote
participation.
Electron-rich
C4-pivaloylated
galactose
building
blocks
show
an
unprecedented
α-selectivity.
trifluoroacetylated
counterpart
with
electron-withdrawing
groups,
on
other
hand,
exhibits
lower
selectivity.
Cryogenic
infrared
spectroscopy
helium
nanodroplets
and
functional
theory
calculations
revealed
existence
dioxolenium-type
intermediates
for
this
reaction,
which
suggests
that
participation
pivaloyl
group
origin
high
α-selectivity
pivaloylated
blocks.
According
to
these
findings,
α-selective
block
glycosynthesis
developed
based
rational
considerations
subsequently
employed
automated
glycan
assembly
exhibiting
complete
stereoselectivity.
Based
obtained
selectivities
glycosylation
reactions
results
from
theory,
we
suggest
mechanism
could
proceed.
The Journal of Organic Chemistry,
Journal Year:
2020,
Volume and Issue:
85(24), P. 15801 - 15826
Published: Oct. 26, 2020
The
stereoselective
synthesis
of
oligosaccharides
remains
one
the
biggest
challenges
in
carbohydrate
chemistry.
Many
factors,
including
reaction
conditions
and
type
glycosyl
donor
acceptor
used,
can
affect
outcome
glycosylation
reactions.
In
this
Perspective,
we
discuss
methods
aimed
to
control
reactivity
stereoselectivity
reactions
using
conformationally
constrained
donors,
with
a
focus
on
more
recently
developed
Angewandte Chemie International Edition,
Journal Year:
2022,
Volume and Issue:
61(21)
Published: March 10, 2022
The
anomeric
configuration
can
greatly
affect
the
biological
functions
and
activities
of
carbohydrates.
Herein,
we
report
that
N-phenyltrifluoroacetimidoyl
(PTFAI),
a
well-known
leaving
group
for
catalytic
glycosylation,
act
as
stereodirecting
challenging
1,2-cis
α-glycosylation.
Utilizing
rapidly
accessible
1,6-di-OPTFAI
glycosyl
donors,
TMSOTf-catalyzed
glycosylation
occurred
with
excellent
α-selectivity
broad
substrate
scope,
remaining
6-OPTFAI
be
cleaved
chemoselectively.
remote
participation
is
supported
by
first
characterization
crucial
1,6-bridged
bicyclic
oxazepinium
ion
intermediates
low-temperature
NMR
spectroscopy.
These
cations
were
found
to
relatively
stable
mainly
responsible
present
stereoselectivities.
Further
application
highlighted
in
reactions
toward
trisaccharide
heparins
well
convergent
synthesis
chacotriose
derivatives
using
bulky
2,4-di-O-glycosylated
donor.
Science Advances,
Journal Year:
2023,
Volume and Issue:
9(42)
Published: Oct. 18, 2023
The
stereoselectivity
of
glycosidic
bond
formation
continues
to
pose
a
noteworthy
hurdle
in
synthesizing
carbohydrates,
primarily
due
the
simultaneous
occurrence
S
Synlett,
Journal Year:
2024,
Volume and Issue:
35(15), P. 1763 - 1787
Published: Jan. 16, 2024
Abstract
Acetal
substitution
reactions
can
proceed
by
a
number
of
mechanisms,
but
oxocarbenium
ion
intermediates
are
involved
in
many
these
reactions.
Our
research
has
focused
on
understanding
the
conformational
preferences,
structures,
and
intermediates.
This
account
summarizes
our
observations
that
electrostatic
effects
play
significant
role
defining
preferred
conformations,
torsional
determine
how
those
react.
Neighboring-group
not
as
straightforward
they
might
seem,
considering
equilibrium
with
structures
involve
stabilization
nearby
substituent.1
Introduction
2
Unexpected
Stereoselectivities
3
Determining
Conformational
Preferences
Oxocarbenium
Ions
4
Structures
Carbocations
NMR
Spectroscopy
X-ray
Crystallography
5
Stereoelectronic
Models
for
Reactions
Involving
Other
6
Stereoselectivity
Reactivity:
When
They
Correlate,
Do
Not
7
Neighboring–Group
Participation
Is
Simple
It
Seems
8
What
True
Carbonyl
Compounds
9
Torsional
Effects
Enolates
10
Summary
Expected
Selectivities
Cyclic
Acetals
11
Conclusion
Communications Chemistry,
Journal Year:
2025,
Volume and Issue:
8(1)
Published: March 7, 2025
The
stereoselective
introduction
of
glycosidic
bonds
is
one
the
greatest
challenges
in
carbohydrate
chemistry.
A
key
aspect
controlling
glycan
synthesis
glycosylation
reaction
which
linkages
are
formed.
outcome
governed
by
a
reactive
sugar
intermediate
-
glycosyl
cation.
Glycosyl
cations
highly
unstable
and
short-lived,
making
them
difficult
to
study
using
established
analytical
tools.
However,
mass-spectrometry-based
techniques
perfectly
suited
unravel
structure
gas
phase.
main
approach
involves
isolating
intermediate,
free
from
external
influences
such
as
solvents
promoters.
Isolation
allows
examining
their
integrating
orthogonal
spectrometric
spectroscopic
technologies.
In
this
perspective,
recent
achievements
gas-phase
research
on
highlighted.
It
provides
an
overview
used
probe
methods
for
interpreting
spectra.
connections
between
data
mechanisms
solution
explored,
given
that
reactions
typically
performed
solution.
Chemistry - A European Journal,
Journal Year:
2022,
Volume and Issue:
28(63)
Published: Aug. 12, 2022
Uronic
acids
are
carbohydrates
carrying
a
terminal
carboxylic
acid
and
have
unique
reactivity
in
stereoselective
glycosylation
reactions.
Herein,
the
competing
intramolecular
stabilization
of
uronic
cations
by
C-5
or
C-4
acetyl
group
was
studied
with
infrared
ion
spectroscopy
(IRIS).
IRIS
reveals
that
mixture
bridged
ions
is
formed,
which
driven
towards
C-1,C-5
dioxolanium
when
C-5,C-2-relationship
cis,
formation
C-1,C-4
dioxepanium
this
relation
trans.
Isomer-population
analysis
interconversion
barrier
computations
show
two
structures
not
dynamic
equilibrium
their
ratio
parallels
density
functional
theory
computed
stability
structures.
These
studies
reveal
how
intrinsic
interplay
different
groups
influences
regioisomeric
products.
