Subject Target molecule , synthetic

Dioxabicyclo[2.2.1]heptane naturally assumed the role of the principal target molecule. It represented a considerable synthetic challenge, for not only is it a strained bicyclic molecule containing the weak and labile 0—0 bond, but it is also a di(secondary-alkyl) peroxide which is the most difficult type to make by classical procedures 12). New synthetic methods of exceptional mildness were clearly needed to solve this problem. In the course of the development of such techniques and from a desire to establish their scope, a variety of saturated bicyclic peroxides have been obtained in addition to 2,3-dioxabicyclo[2.2.1]heptane. The question of how substitution patterns and ring sizes affect the reactivity of bicyclic peroxides has further served to broaden interest in the subject. 

The versatihty of the present furanone synthetic method was demonstrated in the stereoselective synthesis of the Z-isomer of multicolanate (139) [118] (Scheme 26). The prerequisite compound 137 was prepared by successive treatment of appropriate organomagnesium and organohthium reagents, and it was transformed smoothly with lead tetraacetate to the target molecule (the incomplete acetate product 138 was subjected to elimination reaction with DBU). 

A proposal for the synthesis of the target molecule, irrespective of its complexity, can be elaborated by retrosynthetic analysis based on the disconnection approach. For chiral molecules this approach results in a proposal for the synthesis of racemic target molecules. Preparation of one enantiomer, or optically pure target molecule, enables asymmetric synthesis. 1-(Pyridine-3-yl)propan-l-ol is selected to demonstrate various retrosynthetic approaches to this relatively simple target molecule and to show the complexity of asymmetric syntheses of the preferred enantiomer. An introductory example is elaborated in some detail to familiarize the reader with the philosophy behind retrosynthetic analysis and to underline the need for chiral information in the reacting system to complete asymmetric synthesis. Today chiral variants of synthetic reactions are the subject of intensive research, and it is said that their number is limited only by the creativity of the organic chemist. 

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