Self-immolative asymmetric synthesis

It may be of interest to note that the stereospecific transformation shown in equation 15 has been cited as the first reported observation of an 1 - 3 chirality transfer. It is evident that on rearrangement of optically active 6d to 7d, the chiral center at C-a is eliminated and a new one created at C-y. The term self-immolative asymmetric synthesis has also been used to describe syntheses of this kind. As pointed out by Hoffmann , quantitative 1 - 3 chirality transfer will follow from the suprafacial - course of rearrangement, provided the reactant has a uniform configuration at the j8, y-double bond. This stereochemical prediction has also been confirmed by the results obtained in several other [2,3]sigmatropic rearrangements, subsequently reported " . 

A final consequence of the chair transition state is its ability to effect a self-immolative asymmetric synthesis, i.e. the transfer of chirality from a stereogenic carter in the substrate to a new center in the... 

In modem terminology, the core of Marckwald s definition is the conversion of an achiral substance into a chiral, nonracemic one by the action of a chiral reagent. By this criterion, the chiron approach falls outside the realm of asymmetric synthesis. Marckwald s point of reference of course, was biochemical processes, so it follows that modern enzymatic processes [30-32] are included by this definition. Marckwald also asserted that the nature of the reaction was irrelevant, so a self-immolative reaction or sequence such as an intermolecular chirality transfer in a Meerwein-Pondorf-Verley reaction would also be included ... 

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