Synthesis, crystal structure, and molecular conformation of N‐Boc‐L‐Phe‐dehydro‐Leu‐L‐Val‐OCH3
Synthesis, crystal structure, and molecular conformation of N‐Boc‐L‐Phe‐dehydro‐Leu‐L‐Val‐OCH3
复制标题
N-Boc-L-Phe-dehydro-Leu-L-Val-OCH3 的合成、晶体结构和分子构象
作者：
P. Narula;H. C. Patel;T. Singh;Virander S. Chauhan
肽N-Boc-L-Phe-N-Phe-N-Leu-L-瓦尔-OCH 3通过常规后处理程序合成，最后通过将N-Boc-L-Phe-N-Leu-OH偶联至缬氨酸甲酯合成。它在4°C下从甲醇-水混合物的溶液中结晶。晶体属三斜晶系，空间群P1，a = 5.972（5），B = 9.455（6），c = 13.101（6），α = 103.00（4）°，β = 97.14（5）°，γ = 102.86（50）°，V = 690.8（8），Z = 1，dm = 1.179（5）Mg m−3，dc = 1.177（5）Mg m−3。通过使用SHELXS 86的直接方法确定结构。通过块对角最小二乘程序将其精确到1674个观察到的反射的R值为0.060。C2 α -C2 β距离为1.323（9）π，是一个合适的双键长度。C-Leu残基中的键角Cα-Cβ-Cγ为129.4（8）°。肽骨架扭转角为θ1 = −168.6（6）°，ω0 = 170.0（6）°，ω 1 = −44.5（9）°，ω 1 = 134.5（6）°，ω1 = 177.3（6）°，ω 2 = 54.5（9）°，ω 2 = 31.1（10）°，ω2 = 171.7（6）°，ω 3 = 51.9（8）°，3T = 139.0（6）°，θT = −175.7（6）°。这些值表明主链采用β-转角II构象。由于β-转角，在第i个残基的氧和第（i + 3）个残基的NH之间在3.134（6）π的距离处形成分子内氢键。Boc基团具有反式-反式构象。Phe残基的侧链扭转角为χ1 = 171.6（6）°、χ 12，1 =-102.1（9）°和χ 12，2 = 78.6（10）°。α-Leu残基的侧链构象角为χ2 = 2.7（13）°，χ 22，1 = −107.3（11）°，χ 22，2 = 131.3（10）°。定义缬氨酰侧链构象的扭转角χ 31，1和χ 31，2分别为−166.16（6）°和69.1（9）°。晶体结构通过沿着a和B轴的氢键稳定，而货车力是c方向上的稳定相互作用。
The peptide N‐Boc‐L‐Phe‐dehydro‐Leu‐L‐Val‐OCH3 was synthesized by the usual workup procedure and finally by coupling the N‐Boc‐L‐Phe‐dehydro‐Leu‐OH to valine methyl ester. It was crystallized from its solution in methanol–water mixture at 4°C. The crystals belong to the triclinic space group P1 with a = 5.972(5) Å, b = 9.455(6) Å, c = 13.101(6) Å, α = 103.00(4)°, β = 97.14(5)°, γ = 102.86(50)°, V = 690.8(8) Å, Z = 1, dm = 1.179(5) Mg m−3 and dc = 1.177(5) Mg m−3. The structure was determined by direct methods using SHELXS86. It was refined by block‐diagonal least‐squares procedure to an R value of 0.060 for 1674 observed reflections. The C 2α –C 2β distance of 1.323(9) Å in dehydro‐Leu is an appropriate double bond length. The bond angle Cα–Cβ–Cγ in the dehydro‐Leu residue is 129.4(8)°. The peptide backbone torsion angles are θ1 = −168.6(6)°, ω0 = 170.0(6)°, ϕ1 = −44.5(9)°, ψ1 = 134.5(6)°, ω1 = 177.3(6)°, ϕ2 = 54.5(9)°, ψ2 = 31.1(10)°, ω2 = 171.7(6)°, ϕ3 = 51.9(8)°, ψ 3T = 139.0(6)°, θT = −175.7(6)°. These values show that the backbone adopts a β‐turn II conformation. As a result of β‐turn, an intramolecular hydrogen bond is formed between the oxygen of the ith residue and NH of the (i + 3)th residue at a distance of 3.134(6) Å. The Boc group has a trans–trans conformation. The side‐chain torsion angles of the Phe residue are χ1 = 171.6(6)°, χ 12,1 = −102.1(9)°, and χ 12,2 = 78.6(10)°. The side‐chain conformational angles of dehydro‐Leu residue are χ2 = 2.7(13)°, χ 22,1 = −107.3(11)°, and χ 22,2 = 131.3(10)°. The torsion angles χ 31,1 and χ 31,2 that define the conformation of the valyl side chain are −166.16(6)° and 69.1(9)°, respectively. The crystal structure is stabilized by hydrogen bonds along the a and b axes, while the van der Waals forces are the stabilizing interactions in the c direction.
DOI：
10.1111/j.1399-3011.1980.tb02949.x
发表时间：
1980
期刊：
International journal of peptide and protein research
影响因子：
--
作者：
Benedetti,E;Pedone,C;Toniolo,C;Némethy,G;Pottle,MS;Scheraga,HA
通讯作者：
Scheraga,HA
DOI：
10.1111/j.1399-3011.1983.tb02062.x
发表时间：
1983
期刊：
International journal of peptide and protein research
影响因子：
--
作者：
Benedetti,E;Morelli,G;Némethy,G;Scheraga,HA
通讯作者：
Scheraga,HA