STRUCTURE OF NISIN
STRUCTURE OF NISIN
复制标题
DOI：
10.1021/ja00747a073
复制
发表时间：
1971-01-01
影响因子：
15
通讯作者：
MORELL, JL
中科院分区：
文献类型：
--
作者：
GROSS, E;MORELL, JL
因此，5的合成确立了丙酰基烷基末端的位置。内酰胺环的完成可以通过N-2或N-9的酰化，并且C9盐酸盐的剩余结构现在被漏斗化为1和la。C9盐1的滴定显示两个酸性质子，pATa，6.65和p9。05.第一个pKa接近电子类似的嘧啶鎓内酰胺9测定的6.90。C9盐的紫外吸收也表现出两步变化，对应于pH值变化时的两次去质子化。C9游离碱少了一个酸性质子，C9 H10 N6 O2，在甲醇中显示其最长波长最大值为337（13，250），加入碱后移动到353（12，830），表明嘌呤C-9氢解离。C9化合物的酸性和紫外线吸收性与1特别相容，1容纳两个在pH 12以下可解离的氢，而1a在这些条件下仅具有一个可解离的氢。C9化合物1的另一系列降解进一步证实了这种结构归属。当1依次用重氮甲烷、碱、磷和氢碘酸处理时，得到3的N，N-甲基衍生物;
Synthesis of 5 therefore establishes thesite of the propionyl alkyl terminal. Completion of the lactam ring may be via acylation of either N-2 or N-9, and the remaining structures for the C9 hydrochloride are now funneled to 1 and la. Titration of the C9 salt 1 showed two acidicprotons, pATa, 6.65 and p9. 05. The first pKa is close to that of 6.90 determined for the elec-tronically similar pyrimidinium lactam 9. The uv ab-sorption of the C9 salt also exhibited a two-step change corresponding to two deprotonations upon change in pH. The C9 free base with one less acidic proton, C9Hi0N6O2, displayed its longest wavelength maximum at 337 (13,250) in methanol, shifted to 353 (12,830) upon addition of base, indicating the dissociation of the purine C-9 hydrogen.Thus, the acidity and ultraviolet absorptions of the C9 compound are singularly compatible with 1, which accommodates two hydrogens dissociable below pH 12, whereas la has only one hydrogen dissociable under these conditions. This structural assignment was further substantiated by another series of degradations of the C9 compound 1. When 1 was treated successively with diazomethane, alkali, and phosphorus and hy-driodic acid, an vV-methyl derivative of 3 was isolated;