Asymmetric synthesis of alpha-amino acids from alpha,beta-(Z)-didehydroamino acid derivatives with 1,2,3,6-tetrahydropyrazin-2-one structure

Chiral (Z)-alpha,beta -didehydroamino acid (DDAA) derivatives 14, 15 and 16 are obtained from a new chiral iminic cyclic glycine template with 1,2,3,6 -tetrahydropyrazin-2-one structure 10 by condensation with carbonyl compoun ds, Eschenmoser's salt and Bredereck's reagent, respectively. The didehydro alanine derivative 15 and the enaminone 16 can give DDAA derivatives 14 usi ng Heck olefination and vinylic nucleophilic substitution. These DDAA deriv atives 14 and 15 undergo diastereoselective cyclopropanation, 1,3-dipolar a nd Diels-Alder cycloaddition reactions giving, after hydrolysis, the corres ponding cyclic and bicyclic oc-amino acids. (C) 2001 Elsevier Science Ltd. All rights reserved.