Bislactimether method

O-Alkylation of dioxopiperazines with oxonium salts yields bislactim ethers, e.g. 4, which are used as reagents for the asymmetric synthesis of amino acids (bislactimether method, Schollkopf 1979). The chiral bislactim ether 4 is converted into the 6 r-anion 5 (under kinetic control) by n-butyllithium. Alkylation proceeds with high stereoselectivity (greater than 95%). Acid hydrolysis of the alkylation product 6 leads to (unnatural) (R)-mnno acids 7 and recovery of the chiral auxiliary (5)-valine, from which the starting material dioxopiperazine 3 was derived [160]. 

O-Alkylation of chiral dioxopiperazines of type 3 with oxonium salts yields bislactim ethers 4 (cf p. 484), which are used as reagents for the asymmetric synthesis of amino acids (ScHOLLKOPF bislactimether method). 

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