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首页> 外文期刊>Chemistry: A European journal >#gamma#~2-#gamma#~3-and#gamma#~(2,3,4)-Amino Acids , Coupling to #gamma#-Hexapeptide: CD Spectra, NMR Solution and X-ray Crystal Structures of #gamma#-Peptides
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#gamma#~2-#gamma#~3-and#gamma#~(2,3,4)-Amino Acids , Coupling to #gamma#-Hexapeptide: CD Spectra, NMR Solution and X-ray Crystal Structures of #gamma#-Peptides

机译：＃gamma＃〜2-＃gamma＃〜3-和＃gamma＃〜（2,3,4）-氨基酸，与＃gamma＃-六肽偶联：CD光谱，NMR溶液和#gamma的X射线晶体结构＃肽

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摘要

There are numerous possible #gamma#-amino acid with different degrees of sustitution and with various constitutions and configurations. Of these the #gamma#~4-and the like -and unlike#gamma#~(2,4)-amino acids have been previously used as building blocks in #gamma#-peptides. The synthesis of #gamma#~2-#gamma#~3-and#gamma#~(2,3,4)-peptides is now escribed. The corresponding amino acids have been prepared by Michael adition of chiral N-acyl-oxazolidinone enolates to nitro-olefins , with subsequent reduction of the NO_2 to NH_2 groups Such additions to E-2-methyl-nitropropene provide (2R,3R, 4R)-2-alkyl-3-methyl-4-amino-pentanoic acid derivatives(9,10,11) . Stepwise coupling and fragment coupling lead to #gamma#-di, tri-, and hexapeptides(12-23), which werefully characterized. The crystal structures of one of the #gamma#-amino acids(2,3-dimethyl-4-amino-pentanoic acid centre dot HCl, 9a), of a #gamma#~(2,3,4)-di- and a #gamma#~(2,3,4)-tetrapeptide (20,22) are described , and the NMR solution structure in MeOH of a #gamma#~(2,3,4)-hexapeptide(3) has been determined (using TOCSY, COSY, HSQC, HMBC and ROESY)measrements and a molecular dynamics simulated-annealing protocol). A linear conformation(sheet-like) , a novel (M)helix built o nine-membered hydrogen-bonded rings. and (M)2.6_(14) helices have thus been identified . NMR measurements at different temperatures (298-393K) and H/D-exchange rates obtained for the #gamma#~(2,3,4)-hexapeptide are interpreted as evidence for the stability of the 2._(14) (no"melting") and for its-non-cooperative folding mechanism. CD Spectra of the #gamma#-peptides have been measured in MeOH and CH_3CN, indicating that only the protected and unprotected #gamma#~(2,3,4) hexapeptide is prresent as the 2.6_(14) helix in solution . The structures of the #gamma#~2- and #gamma#~3- hexapeptides(1,2) could not be determined
机译：有许多可能的＃γ＃-氨基酸具有不同的饱和度和不同的结构和构型。在这些之中，＃γ4〜等与＃γ2（4，4）-氨基酸不同，先前已被用作＃γ＃肽中的结构单元。现在描述＃gamma＃〜2-＃gamma＃〜3-和＃gamma＃〜（2,3,4）-肽的合成。通过手性N-酰基-恶唑烷酮烯醇酸酯与硝基烯烃的迈克尔加成反应，随后将NO_2还原为NH_2基团，制备了相应的氨基酸。向E-2-甲基-硝基丙烯中的这种添加提供了（2R，3R，4R） -2-烷基-3-甲基-4-氨基戊酸衍生物（9,10,11）。逐步偶联和片段偶联产生了＃gamma＃-di，tri-和hexapeptide（12-23），这些肽已得到充分表征。 ＃gamma＃〜（2,3,4）-di-和＃gamma＃-氨基酸（2,3-二甲基-4-氨基戊酸中心点HCl，9a）的晶体结构描述了＃gamma＃〜（2,3,4）-四肽（20,22），并确定了＃gamma＃〜（2,3,4）-六肽（3）在MeOH中的NMR溶液结构。 （使用TOCSY，COSY，HSQC，HMBC和ROESY）测量和分子动力学模拟退火协议）。线性构型（片状），新颖的（M）螺旋构筑有九元氢键合环。和（M）2.6_（14）个螺旋因此被确定。 ＃gamma＃〜（2,3,4）-六肽在不同温度（298-393K）和H / D交换速率下的NMR测量被解释为2 ._（14）稳定性的证据（否“熔化”）及其非合作性折叠机制。已经在MeOH和CH_3CN中测量了＃γ＃肽的CD光谱，表明仅存在保护和未保护的＃γ＃（（2,3,4））六肽作为溶液中的2.6_（14）螺旋。无法确定＃gamma＃〜2-和＃gamma＃〜3-六肽（1,2）的结构

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