Diastereoselectivity Overman rearrangement

Stereoselective rearrangement reactions can involve sugar-linked functionalities. An example of this type is the Overman rearrangement of allylic trichloracetimidates formed from a D-glucofuranose derivative 20 [36]. This methods affords (L)-a-ami-no acids 25 from (Z)-allylic imidate 23 and (R)-a-amino acids 25 from ( )-imidates 23 with a diastereoselectivity of about 16 1. The oxidative cleavage of compound 24 with Ru04 yields the a-amino acid 25, (Scheme 15). 

A synthesis of broussonetine F from diethyl L-tartrate has been achieved via an orthoamide Overman rearrangement, which provided an allylic amino alcohol with complete diastereoselectivity (Scheme 97). (g)... 

Overman s discovery of the rearrangement of trichloroacetimidates [16, 39, 40] ushered in a powerful new method for the synthesis of alkaloids. A clever implementation of this transformation was reported in Danishefsky s synthesis of the antitumor agent pancratistatin (86, Scheme 16.9) [70]. Thermal rearrangement of imidate 84 led to amide 85, hence installing the key amine to become part of the lactam in the natural product and setting the stage for a subsequent diastereoselective dihydroxylation. 

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