Glycylglycine, glycyl‐(S)‐alanine, and (S)‐alanylglycine esters are cyclized through pivalaldehyde imines to give dipeptide‐derived 3‐(benzyloxycarbonyl)‐2‐(tert‐butyl)‐5‐oxoimidazolidine‐1‐acetates 1–3. These are alkylated diastereoselectively by Li‐enolate formation and addition of alkyl bromides or iodides (products 4–6). Starting from (S)‐alanine and glycine, (S)‐alanyl‐(S)‐alanine or (R)‐alanyl‐(R)‐alanine, and (R)‐alanyl‐(R)alanyl‐(S)‐alanine‐ have thus been prepared, with the (tert‐butyl)‐substituted N,N‐acetal center playing the role of a pivot or lever for diastereoselective formation of new stereogenic centers under kinetic or thermodynamic control.
ASJC Scopus subject areas
- Drug Discovery
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry