多肽合成中困难序列的缩合研究进展(3)

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

backbone

amidebondsofseveralresiduesbeforetheidentifiedexpected“difficult

sequences”in

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

(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

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

procedure.disrupt

thatthepresenceofHmbunitevery6—7residuesis

aggregation,anotherprotection

is

to

methodbackbone

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

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