27 March 2010

Ring Expansion Strategy

In, First Total Synthesis and Structural Confirmation of Fluvirucinine A2 via an Iterative Ring Expansion Strategy, the authors describe a really interesting strategy depicted in their diagram, below.

Preparing large sized rings (lactams, lactones) can be quite a chore. As the size of the required ring increases, the propensity for ring closure diminishes; instead, dimerization, trimerization etc occurs as competing side reactions. In order to avoid the formation of these side reactions high dilution conditions are required.

These high dilution conditions are avoided when this strategy is used. Further, the stereochemical control inherent in the mechanism of the aza-Claisen rearrangement has been used in this particular example.

Impressive.

(Note that my analysis is based upon the abstract and not the full paper).

Mechanistic details found in, SYNTHETIC COMMUNICATIONS, 26(9), 1675-1680 (1996).

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