(S,S)-(+)-Pseudoephedrine as chiral auxiliary in asymmetric conjugate addition and tandem conjugate addition/α-alkylation reactions

[GRAPHICS] Organolithium reagents undergo highly regio- and diastereoselective 1,4-addition to (S,S)-(+)-pseudoephedrine enamides furnishing the corresponding, beta-alkyl-substituted adducts in excellent yields and diastereoselectivities. In addition, the intermediate lithium enolates generated after the conjugate addition step undergo a highly diastereoselective alkylation reaction, furnishing alpha,beta-dialkyl-substituted amides in high yields. The obtained adducts have been converted into chiral nonracemic beta-alkyl- and alpha,beta-dialkyl-substituted carboxylic acids and gamma-alkyl- and beta,gamma-dialkyl-substituted alcohols using very simple and high-yielding procedures.