Nakamura H, Lee S, Ono S, Kato T, Aoyagi H
Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka, Japan.
Int J Pept Protein Res. 1990 Nov;36(5):471-5. doi: 10.1111/j.1399-3011.1990.tb01308.x.
Formation of by-products of pyrenylalanine-peptides was observed during the cleavage of a tosyl group in pyrenylalanine-peptides containing an Arg(Tos) residue with HF. NMR and fluorescence experiments showed that by-products were compounds in which a pyrenyl group was modified with a tosyl group(s). The side reaction was little suppressed by the addition of usual scavengers such as anisole, 1,2-ethanedithiol, thioanisole and p-cresol. Under the conditions used for the cleavage of N alpha-Boc group, i.e., trifluoroacetic acid or 4 M HCl in dioxane, the pyrenylalanine residue was stable. No side reaction was, furthermore, observed in the reductive cleavage with sodium in liquid ammonia. These results suggest that the side reaction may be due to an electrophilic attack of tosyl cations to the electron-rich pyrenyl group in the pyrenylalanine residue under the HF-mediated acidic conditions.
在用HF裂解含有Arg(Tos)残基的芘基丙氨酸肽中的甲苯磺酰基时，观察到了芘基丙氨酸肽副产物的形成。核磁共振（NMR）和荧光实验表明，副产物是芘基被一个或多个甲苯磺酰基修饰的化合物。加入常用的清除剂如苯甲醚、1,2 - 乙二硫醇、硫代苯甲醚和对甲酚后，该副反应几乎没有受到抑制。在用于裂解Nα - Boc基团的条件下，即三氟乙酸或二氧六环中的4 M盐酸中，芘基丙氨酸残基是稳定的。此外，在液氨中用钠进行的还原裂解中未观察到副反应。这些结果表明，该副反应可能是由于在HF介导的酸性条件下，甲苯磺酰阳离子对芘基丙氨酸残基中富电子的芘基进行亲电攻击所致。
