SYNTHETIC APPROACHES TO LANKAMYCIN AND ROSARAMICIN

兰卡霉素和罗沙米星分别为14元和16元大环内酯类化合物 它们属于广泛应用于临床和兽医的抗生素家族 练习一下。这一因素，加上它们复杂的、多功能的骨骼 事实证明，合成有机化学家和许多进展对合成有机化学家具有吸引力 方法学是针对它们的合成所做的努力的结果。 以糖为基础的合成大环内酯类化合物的方法在 过去五年，但这一概念的吸引力受到 限制(大多数)糖的长度只有五六个碳单位， 以及用于将两个糖亚单位连接在一起的规定 产生丰富的非对映异构体混合物。因此，通过以下方式获得的任何优势 不同亚单位的立体选择性合成被形成否定 这种非对映异构体混合物在合成的后期阶段。 为了克服这些缺点，提出了一种基于“折叠”的方法 “糖苷”概念正在开发中，它具有相当大的手性。 经济上的不对称中心在糖部分上不会被浪费， 相反，目标分子上的不对称中心被制成 与糖部分的不对称中心重合。

Lankamycin and rosaramicin are respectively 14 and 16 membered macrolides which belong to antibiotic families widely used in clinical and veterinary practice. This factor, added to their complex, polyfunctional skeleta have proved alluring to synthetic organic chemists and many advances in methodology have resulted from efforts directed towards their syntheses. Sugar-based approaches to macrolide synthesis have become popular within the past five years, but the attractiveness of the concept suffers from the limitation that (most) sugars are only five or six carbon units in length, and provisions for connecting two sugar subunits together invariably produce rich mixtures of diastereomers. Thus, any advantages gained by stereoselective syntheses of various sub-units are negated by the formation of such diastereomeric mixtures at advanced stages of the synthesis. In order to overcome these shortcomings, an approach based on "folded glycoside" concept is being developed which features considerable chiral economy in that asymmetric centers on the sugar moieties are not "wasted", and conversely, asymmetric centers on the target molecule are made to coincide with asymmetric centers on the sugar portion.