多肽合成中困难序列的缩合研究进展(3)
发布时间:2021-06-08
发布时间:2021-06-08
非常详细的综述性文章
HANXiang,etal:Recent
progressintheimprovementofthecouplingefficiency
peptidesynthesis
of“difficultsequences’’in
’113
sequences”is
reversibleamide—backbonesubstitution.involvesN—substitution
of
one
leeular
reactive
acyltransfer
mechanism.Moreover
themore
Thisstrategy
ormore
or
Hnb(2一hydroxy-4一nitrobenzyl)
auxiliaries
have
been
uses
a
backbone
amidebondsofseveralresiduesbeforetheidentifiedexpected“difficult
sequences”in
a
protecting
introduced(Figure
nitrosame
peptide
is
to
31[13-.TheHnb
assist
auxillaryand
substituenttoadvantageous
sequences”.
encountered.Amide—backbonesubstitutionappears
prevent
or
acyltransfer
as
hasthe
disrupttroublesomeintermolecularhydrogen—
native
effectHmbfor
to
overcoming“difficult
bondingnetworksbythe
removaloftheamide
Compared
the
Hmbauxiliary,obviously
improved
hydrogenbondafterN—substitution,whichalterationofthebackboneconformationistionoftertiaryamidebonds.
The
solubility
improvement
is
attributed
to
acyltransferreactivity,especiallybranched
amino
acids,with
the
betweenlargeor卢一Hnbauxiliary
of
was
causedbytheintroduc—
obtained(Figure4).After
the
sequence,the
temporary
synthesisexpected
can
protectinggroupHnb
at
be
existenceoftertiaryamidebonds,X一(Z)Y,whereXandY
are
convenientlyremovedbymildphotolysisThe
oxidative—reductive
safety
catch
366nm[141.SiMb
arbitraryamino
acidresiduesandZis
a
(3一
temporary
causes
protectinggroup.The
of
tertiaryamide
structure
bondthethiscalled
methylsulfinyl-4一methoxy一6一hydroxybenzyl)backbone
auxiliaryalso
can
disturbanceof
tertiary
the卢一sheet
amide
bond
by
usedforthispurpose(Figure3)’15|.
rotation
plane
and
TheAib(o/。aminoisobutvricacid)residueusedin
peptidesynthesisisanothereffect.TheabilityofAibthe
solvation
of
to
case
segmentation“peptide
from卢一sheet
segment
structureswasthat
can
offerthePSS
separation
(PSS)”.Drab
is
promote
helicalfoldingand
in
(dimethoxybenzyl)Ⅳ“一auxiliary
backbone
substitutionin
this
to
thefirstamide—
Z—Aib5一Leu—Aib2一OMe
DMSO
strategy.Thisapproach
(dimethylsulfoxide)wasconfirmedbyNMR‘”1.Pro
is
hadbeenmainlydesignedthe
Drab
as
a
avoidaggregationbyusing
able
to
create
alsoclassified
or
intoPSS
residue,considering
interaction
the
to
bulkygroup
steric
shortrange
intrachain—backbonedue
hindrance.Aftersynthesisofexpectedsequence,thetemporaryprotectinggroupDmbbyacidolysis.
Theotherapproach
on
can
thelowflexibilityofthepyrrolidineringofProresidue
to
beeasilyremoved
breakthe8一sheetplane.InsolubilityofpeptiderichAsnisessentiallycausedbya口一sheetaggregation,
to
in
backboneprotectinggroups
is
andisverydifficultofPro
beprepared.Butthesynthesis
whichwillpreventtheformationofhydrogenbondsthe
introduction
01'1
insertedpoly一(Ash—Ala—Asn一—Pr—o—Asn—Ala—Asn—
was
ofthe
Hmb(2-hydroxy-4一methoxy—
shown
Pro)q
liquid
carriedoutwithout
Since
Pro
anyis
to
troubleknownachieve
by
to
routine
benzyl)group
thenitrogen‘11。.Ithasbeen
a
procedure.disrupt
thatthepresenceofHmbunitevery6—7residuesis
aggregation,anotherprotection
is
to
methodbackbone
a
sufficient
to
disruptthepeptideaggregation.Attheend
introduce
dipeptides
or
containing
ofthesynthesistheHmbgroupisremovedduringthefinal
TFA
pseudoprolineresiduefromSeroftheduring
synthesis,thethe
final
Ser
or
ThrⅢ。.Atwill
be
theend
cleavage.The
effectiveness
has
ofbackbone
Thr
regenerated
work
to
substitutionwiththe
limbauxiliary
beendemon—TFA
cleavage
step.Recent
stratedbytheimprovedFmocsynthesesofa“difficult”peptide
showedthatintroductionofpseudoprolinesissuperiorHmbbackboneprotection
A口(1—40).ForFmocSPPS,Clippingdale
as
indisruptingaggregates。”。.
allowsthe
stepwise
or
andco.workers[J21introducedtheHmbN“一auxiliaryTheintroductionofpseudoproline
amide—backbone
requirement
for
substitution(Figure
this
approach
is
3).
Aof
keythe
SPPSoflongpeptides。“.EsterificationofSerwillefficientlydisruptaggregation
as
Thr
N—acylation
an
well.Theresulting
subsequentsecondaryN“一amineby
0—}Nintramo—
H0
Ho
/0
SiMb
Figure3
ThestructureofN—auxiliariesusedtoovercome“difficultsequences’’inSPPS