A substantial number of compounds that have been discovered from natural sources exhibit significant physiological properties. Methods to prepare these materials in highly efficient and stereocontrolled manner can provide access to these often rare substances. During the course of these synthesis investigations, opportunities arise to discover structural and reactivity features of the natural product that are relevant to the attractive biological property. Combining this knowledge with the newly developed methods for their preparation provides a formula for acquiring new materials of interest to chemistry, biology and medicine. Many of these naturally occurring compounds contain chains within their structure. The stereocontrolled preparation of these materials via the simultaneous extension of chains in two directions is an attractive strategy since the number of transformations can be reduced relative to the one-directional chain synthesis. However, the termini of the newly synthesized chain will in most cases require differentiation. Group selective transformations can solve this problem while simultaneously bringing additional desirable features to the synthesis. For example, these reactions will be employed in several asymmetric syntheses that allow an achiral starting material to be converted into the target system or its antipode with enantioselectivities that are greater than 109:1. The symmetry properties of chains within subunits of the target systems that are required for the application of this strategy have been identified. A discussion of the issues associated with the synthesis of each of the three classes of chains and the differentiation of the termini has been provided. A major objective of this effort is to establish both the desirability and generality of the strategy. Accordingly, plans are presented to prepare materials by employment of this strategy from a range of classes that include macrolide antibiotics, polyene macrolide antifungals, carbohydrates and polyether anticoccidials and antibiotics. The two directional chain synthesis strategy promises to be efficient and highly enantioselective.
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