Pang C P, White R L, Abraham E P, Crout D H, Lutstorf M, Morgan P J, Derome A E
Biochem J. 1984 Sep 15;222(3):777-88. doi: 10.1042/bj2220777.
'Chiral methyl valines', i.e. samples of valine labelled stereospecifically in the methyl groups with 2H and 3H, were incorporated into cephalosporin C by a suspension of washed cells of Cephalosporium acremonium. Analysis by 3H n.m.r. of the cephalosporin C produced showed that the conversion of the 3-pro-S-methyl group of valine into the acetoxymethyl side-chain was a highly stereospecific process. By contrast, conversion of the 3-pro-R-methyl group into the endocyclic methylene group of the dihydrothiazine ring was shown to proceed by a non-stereospecific process.
“手性甲基缬氨酸”,即甲基被2H和3H立体定向标记的缬氨酸样品,通过顶头孢霉洗涤细胞的悬浮液被掺入头孢菌素C中。对所产生的头孢菌素C进行的3H核磁共振分析表明,缬氨酸的3-前-S-甲基转化为乙酰氧基甲基侧链是一个高度立体特异性的过程。相比之下,3-前-R-甲基转化为二氢噻嗪环的环内亚甲基则显示是通过一个非立体特异性过程进行的。