Organic Letters,
Journal Year:
2024,
Volume and Issue:
unknown
Published: Dec. 2, 2024
A
remote
carbonyl
group
up
to
six
atoms
away
from
the
acetal
can
induce
1,2-asymmetric
induction
in
nucleophilic
substitution
reactions
of
acyclic
acetals.
Isolation
a
cyclic
carbonate
under
Lewis
acidic
conditions
and
computational
studies
suggested
that
participated
through
formation
dioxocarbenium
ion
intermediate.
The
stereochemical
outcomes
depended
on
size
alkyl
substituent
nucleophile
employed.
The Journal of Organic Chemistry,
Journal Year:
2024,
Volume and Issue:
89(3), P. 1618 - 1625
Published: Jan. 18, 2024
Minimal
structural
differences
in
the
structure
of
glycosyl
donors
can
have
a
tremendous
impact
on
their
reactivity
and
stereochemical
outcome
glycosylation
reactions.
Here,
we
used
combination
systematic
reactions,
characterization
potential
reactive
intermediates,
in-depth
computational
studies
to
study
disparate
behavior
systems
involving
benzylidene
glucosyl
mannosyl
donors.
While
these
been
studied
extensively,
no
satisfactory
explanations
are
available
for
observed
between
3-
Journal of the American Chemical Society,
Journal Year:
2023,
Volume and Issue:
145(48), P. 26190 - 26201
Published: Nov. 27, 2023
The
stereoselective
introduction
of
glycosidic
bonds
(glycosylation)
is
one
the
main
challenges
in
chemical
synthesis
carbohydrates.
Glycosylation
reaction
mechanisms
are
difficult
to
control
because,
many
cases,
exact
reactive
species
driving
product
formation
cannot
be
detected
and
outcome
explained
by
primary
intermediate
observed.
In
these
reactions
expected
take
place
via
other
low-abundance
intermediates
that
rapid
equilibrium
with
a
Curtin-Hammett
scenario.
Despite
this
principle
being
well-known
organic
synthesis,
mechanistic
studies
investigating
model
glycosylation
complicated
challenge
detecting
extremely
short-lived
responsible
for
formation.
Herein,
we
report
utilization
between
stable,
readily
observed
α-glycosyl
triflate
order
infer
structure
former
employing
exchange
NMR.
Using
technique,
enabled
detection
such
as
β-glycosyl
triflates
glycosyl
dioxanium
ions.
This
demonstrates
power
NMR
unravel
aim
build
catalog
kinetic
parameters,
allowing
understanding
eventual
prediction
reactions.
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
Molecules,
Journal Year:
2025,
Volume and Issue:
30(2), P. 218 - 218
Published: Jan. 7, 2025
Using
methods
of
DFT,
we
investigated
the
effect
electron
withdrawing
and
donating
groups
on
relative
stability
tentative
glycosyl
donor
reaction
intermediates.
The
calculation
shows
that
by
changing
stereoelectronic
properties
protecting
group,
can
influence
dioxolenium
type
intermediates
up
to
10
kcal
mol−1,
increasing
nucleophillicity
4-O-Bz
intermediate
becomes
more
stable
than
a
triflate–donor
pair.
We
exploited
this
mechanism
design
galactosyl
donors
with
custom
O2
O4,
outcome
cyclohexanol.
showed
no
change
in
product
distribution,
which
suggests
neighboring
group
participation
takes
precedence
over
remote
due
kinetic
barriers.
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:
2024,
Volume and Issue:
unknown
Published: Sept. 2, 2024
Abstract
A
key
challenge
in
oligosaccharide
synthesis
is
the
stereoselective
installation
of
glycosidic
bonds.
Each
linkage
has
one
two
possible
stereo‐chemical
geometries,
α/β
or
1,2‐
cis
/
trans
.
An
established
approach
to
install
bonds
neighboring
group
participation
(NGP),
mediated
by
a
2‐
O
‐acyl
group.
Extension
this
intramolecular
stabilization
nucleophilic
groups
located
at
more
remote
positions
also
been
suggested,
but
remains
poorly
understood.
Previously,
we
employed
infrared
ion
spectroscopy
characterize
molecular
ions
monoacetylated
sugar
donors
and
showed
how
strength
stabilizing
effect
depends
on
position
participating
ester
glycosyl
donor
ring
as
well
its
relative
stereochemistry.
In
work,
investigated
carrying
acyl
groups.
Using
isotope
labelling
isomer
population
analysis
were
able
resolving
spectra
isomeric
mixtures
establish
contribution
individual
species.
We
conclude
that
3,4‐diacetyl
mannosyl
exclusively
form
dioxanium
result
C‐3
stabilization.
contrast,
glucosyl
galactosyl
cations
C‐4
products.
Hence,
combination
labeling
allows
for
study
increasingly
complex
cations.
Journal of the American Chemical Society,
Journal Year:
2024,
Volume and Issue:
147(1), P. 932 - 944
Published: Dec. 18, 2024
One
of
the
main
challenges
in
oligosaccharide
synthesis
is
stereoselective
introduction
glycosidic
bond.
In
order
to
understand
and
control
glycosylation
reactions,
thorough
mechanistic
studies
are
required.
Reaction
intermediates
found
by
NMR
spectroscopy
often
cannot
explain
glycosylation's
stereochemical
outcome.
Hence,
reactions
may
proceed
through
low-abundance
reaction
that
difficult
detect,
according
a
Curtin–Hammett
scenario.
We
have
previously
observed
manno-type
sugars
can
engage
C-3
acyl
neighboring
group
participation.
Herein,
we
report
detection
glycosyl
dioxanium
ions
result
from
participation
mannuronic
acid
donors.
Using
suite
exchange
techniques,
were
able
dissect
kinetics
conformational
ring-flip
precedes
event
itself
various
sugars.
this
study
provides
complete
picture
mannosyl
ion
formation.
European Journal of Organic Chemistry,
Journal Year:
2023,
Volume and Issue:
27(7)
Published: Dec. 7, 2023
Abstract
The
outcome
of
glycosylation
reactions
heavily
relies
on
the
specific
protecting
group
patterns
employed
both
donor
and
acceptor
molecules.
picoloyl
(Pico)
stands
out
as
it
can
steer
stereoselectivity
in
a
reaction
through
hydrogen
bond‐mediated
aglycone
delivery
(HAD).
This
provides
syn
‐stereoselectivity,
with
respect
to
stereochemistry
Pico
group,
by
forming
bond
between
incoming
ring
nitrogen.
We
here
probe
how
acidity
influences
stereodirecting
effect
group.
A
set
3‐
O
‐functionalized
glucosyl
mannosyl
donors,
each
bearing
different
groups
(picolinate,
nicotinate,
isonicotinate,
benzoate),
were
synthesized
for
systematic
evaluation.
For
‐picoloyl‐glucose
series,
exhibited
minimal
influence
stereoselectivity,
only
weak
nucleophiles
showing
modest
shift
selectivity
‐Pico
protected
comparison
other
C‐3‐acyl
glucosides.
In
contrast,
‐picoloyl‐mannose
series
much
stronger
β‐directing
was
observed,
wherein
more
acidic
acceptors
led
increased
β‐selectivity.
results
provide
insights
into
complex
interplay
mediated
Molecules,
Journal Year:
2024,
Volume and Issue:
29(19), P. 4710 - 4710
Published: Oct. 4, 2024
An
efficient
and
versatile
glycosylation
methodology
is
crucial
for
the
systematic
synthesis
of
oligosaccharides
glycoconjugates.
A
direct
intermolecular
an
indirect
intramolecular
have
been
developed,
former
can
be
applied
to
medium-to-long-chain
glycans
like
that
nucleotides
peptides.
The
development
a
generally
applicable
approach
stereoselective
construction
glycosidic
bonds
remains
major
challenge,
especially
1,2-
