Lichtor Phillip A, Miller Scott J
Department of Chemistry, Yale University , P.O. Box 208107, New Haven, Connecticut 06520, United States.
J Am Chem Soc. 2014 Apr 9;136(14):5301-8. doi: 10.1021/ja410567a. Epub 2014 Apr 1.
We describe mechanistic investigations of a catalyst (1) that leads to selective epoxidation of farnesol at the 6,7-position, remote from the hydroxyl directing group. The experimental lineage of peptide 1 and a number of resin-bound peptide analogues were examined to reveal the importance of four N-terminal residues. We examined the selectivity of truncated analogues to find that a trimer is sufficient to furnish the remote selectivity. Both 1D and 2D (1)H NMR studies were used to determine possible catalyst conformations, culminating in proposed models showing possible interactions of farnesol with a protected Thr side chain and backbone NH. The models were used to rationalize the selectivity of a modified catalyst (17) for the 6,7-position relative to an ether moiety in two related substrates.
我们描述了一种催化剂（1）的机理研究，该催化剂能使法尼醇在远离羟基导向基团的6,7位发生选择性环氧化反应。对肽1和一些树脂结合的肽类似物的实验谱系进行了研究，以揭示四个N端残基的重要性。我们研究了截短类似物的选择性，发现三聚体足以提供远程选择性。使用一维和二维（1）H NMR研究来确定可能的催化剂构象，最终提出的模型显示了法尼醇与受保护的苏氨酸侧链和主链NH之间可能的相互作用。这些模型用于解释修饰催化剂（17）相对于两种相关底物中醚部分对6,7位的选择性。
