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In the absence of water, an excess of the lithium enolate of
N-(diphenylmethylene)glycine ethyl ester (
4) adds to sulfinimines to give
syn-2,3-diamino esters
6, and in the presence of water, this enolate gives the
anti-2,3-diamino esters
5. These unusual results are interpreted interms of those factors that inhibit the retro-Mannich fragmentation in the diamino esters.