由化学方法证明创新霉素的绝对构型为3S,4R,如式1所示.与已知具有相同骨架的抗生素indolmycin(7)的绝对构型相反,为生源方面饶有兴趣的问题.去甲创新霉素(14)的羧基及去羧创新霉素(18)的甲基均以横键为最佳构象,因此似无顶端(anomeric)效应.由此可以推断创新霉素在溶液中较大的羧基是横键,甲基是竖键.这一点与固态X 衍射结果一致. The absolute configuration of the neomycin is chemically confirmed as 3S, 4R, as shown in Equation 1. Contrary to the absolute configuration of the antibiotic indolmycin (7), which is known to have the same backbone, there are intriguing questions for students. The carboxyl group of norcinomycin (14) and the methyl group of decarboxylated neomycin (18) are both optimally cross-linked and thus appear to have an anomeric effect, from which it can be inferred that neomycin is more soluble in solution A large carboxyl group is a horizontal bond and a methyl group is a vertical bond, which is consistent with the result of solid-state X-ray diffraction.