Strategy acyclic stereogenic centers

An investigation into the preparation of n = 2 telomers was successful in showing that the ACT strategy with templates of type 14 is a viable means for producing isotactic 1,3 stereocenters as exemplified in the production of 16 (n=2) (Scheme 8-5). The oxazolidine unit has documented success as a stereocontrol element in acyclic radical reactions [35-37], and thus its incorporation into this template provides, in effect, a chiral auxiliary to control the configuration of new stereogenic centers formed in the sequence. 

This synthesis illustrates one strategy for the preparation of acyclic molecules containing multiple stereogenic centers — use cyclic structures to control stereochemistry and then liberate the acyclic structure. The strategy is not unlike several of the Cecropia juvenile hormone syntheses we examined, where stereoselective olefin synthesis was the goal. Whereas three pieces are ultimately assembled, the synthesis of the central fragment is linear and there was a price to pay for this approach. It is long. 

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