SYNTHETIC APPROACHES TO LANKAMYCIN AND ROSARAMICIN

兰卡霉素和罗萨霉素分别为14元和16元大环内酯类 其属于广泛用于临床和兽医的抗生素家族， 实践 这个因素，加上他们的复杂，多官能的β， 证明了对合成有机化学家的吸引力， 这些方法是通过努力综合而成的。 基于糖的大环内酯合成方法已经变得流行， 在过去的五年里，但这一概念的吸引力受到了 限制是（大多数）糖的长度仅为5或6个碳单元， 以及将两个糖亚基连接在一起的条件 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 各种亚基的立体选择性合成被形成 这种非对映异构体混合物在合成的高级阶段。 为了克服这些缺点，提出了一种基于“折叠 糖苷”概念正在发展，其具有相当大的手性 经济性在于糖部分上的不对称中心没有被“浪费”， 相反，靶分子上的不对称中心被制造成 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.