AMINO ACID LABELING FOR LARGER PROTEINS METHYL GROUP LABELING

正如我们在最初的提案中所讨论的，蛋白质中的甲基 对于较大蛋白质的核磁共振结构研究是至关重要的。的确有 质子的化学位移范围有相当大的重叠 氨基酸中甲基的共振谱对氨基酸的拆分 甲基质子很难。此外，只有微不足道的 缬氨酸和亮氨酸残基中的前手性甲基可制得 没有同位素歧视。而差分“C-标记法” 缬氨酸的前手性甲基可用于指认 目的，碳维度中的化学位移分散使 希望用13C标记缬氨酸和/或亮氨酸中的甲基。 因此，我们的计划是用13C标记所有的甲基 ，并通过引入前手性甲基来区分 不同的氚标签。我们已经制定了一项针对 缬氨酸手性甲基标记化合物的合成。差异化的 以克为单位生产的氢化甲基碘。这个 丙氨酸的异丙基侧链是用立体选择性 奥波尔泽舒坦手性助剂。我们现在正处于最后阶段 制备标记的valine，并将其整合到Trp中 很快就会成为抑制者。此外，还取得了重大进展。 指向标记此路径的新路径将允许差异化 咪唑类氮基的标记及其手性诱导 A-氨基。

As discussed in our original proposal methyl groups in proteins are pivotal for NMR structural studies on larger proteins. There is considerable overlap in the chemical shift range of the proton resonances of methyl groups in amino acids making resolution of the methyl protons difficult. In addition, only tenuous assignments of the prochiral methyls in valine and leucine residues can be made without isotopic discrimination. While differential "C-labeling of the prochiral methyls of valine has been useful for assignment purposes, the chemical shift dispersion in the carbon dimension makes it desirable to label both methyls in valine and/or leucine with 13C . Therefore, we our plan was to label all of the methyl groups with 13C , and distinguish the prochiral methyl groups by introducing differential deuterium labels. We have developed the a scheme for the synthesis of the chiral methyl labeling in valine. Differentially deuterated methyl iodides have been produced in gram quantities. The isopropyl side chain of valine is produced stereoselectively using the Oppolzer sultam chiral auxiliary. We are now in the final stages of preparing the labeled valine and will incorporate it into the Trp repressor soon. In addition, significant progress has been made toward a new route to labeled This route will allow differential labeling of the imidazole nitrogens and chiral induction of the a-amino group.