New Methodology for Multiple Contiguous Chiral Centers (Chemistry)

抗生素代表了一个非常重要的类别， 生物活性分子，其中一些具有强烈的 与某些碳水化合物在化学和结构上的相似性。 有机和高分子化学项目的资助 旨在利用它们作为廉价和有效的 某些种类的抗生素的原料， 水痘链球菌素 该研究项目的总体目标是开发 有效利用容易获得的碳水化合物衍生物 在有机合成中。 试验场是安莎连锁店， 静脉曲张链球菌素A 描述了两种不同的方法。 的 第一个是正在进行的，涉及一个被称为吡喃糖苷的过程， 同源化，其中糖被加工成双-和 由此得到三吡喃糖，其连续碳主链 /提供所需的立体基因中心数。 的 第二种方法是一个趋同的过程，计划使 使用一个显着的羟醛缩合，已被发现 在早期的工作中。 底物3-酮吡喃糖苷本身是 值得注意的是，它没有显示出倾向于β 淘汰 这种出乎意料的稳定性仅仅是 在这些过程中遇到的几个特质， 调查显示， 碳水化合物和碳环， 用现有理论来“解释” 一项重大努力是 因此，针对这些系统的调查， 特质，采用理论和 实验方法，适当的支持， 计算机辅助建模技术。

The antibiotics represent an extremely important class of biologically active molecules, some of which bear strong chemical and structural similarities to certain carbohydrates. This grant in the Organic and Macromolecular Chemistry Program is directed toward utilizing them as cheap and efficient starting materials for certain classes of antibiotics such as the streptovaricins. The general objective of this research program is to develop the efficient use of readily available carbohydrate derivatives in organic synthesis. The testing ground is the ansa chain of streptovaricin A. Two different approaches are described. The first, in progress, involves a process known as pyranosidic homologation in which the sugar is elaborated into a bi- and thence a tri-pyranose, whose continuous carbon backbone /provides the required number of stereogenic centers. The second approach is a convergent process, which plans to make use of a remarkable aldol condensation that has been uncovered in earlier work. The substrate, a 3-keto pyranoside, is itself remarkable in that it shows no inclination toward beta elimination. This unexpected stability is merely one of several idiosyncracies encountered in the course of these investigations, which reveal striking differences between carbohydrates and carbo-cycles that are not satisfactorily "explained" by current theories. A substantial effort is therefore directed toward a systematic investigation of these idiosyncracies, employing a combination of theoretical and experimental methods, buttressed by appropriate computer-assisted modelling techniques.