Highly diastereoselective Michael addition reactions of butane-2,3-diacetal desymmetrized glycolic acid. Preparation of alpha-hydroxy-gamma-amino acid derivatives

[GRAPHICS] The butane-2,3-diacetal (BDA) desymmetrized glycolic acid building block un dergoes efficient and highly diastereoselective lithium enolate Michael add itions to alpha,beta -unsaturated ketones, lactones, and nitro olefins. Sub sequent deprotection of these Michael adducts gives a-hydroxy acids in very high yield. Hydrogenation of the nitro group in some of the adducts leads to gamma -lactams, which can be easily converted into alpha -hydroxy-gamma -amino acid derivatives.