The formation of β-lactam derivatives and a C3-symmetrical heterocycle from 5,6-dihydro-2H-1,3-oxazines

In this article a short approach towards highly functionalized β-lactam derivatives is described. Diastereoselective addition of malonic acid to 5,6-dihydro-2H-1,3-oxazines leads to the corresponding saturated carboxymethyl derivatives. After hydrolysis of the O,N-acetal to the β-amino acids, these are transformed to β-lactam derivatives via the Ugi-reaction. Depending on the bulkyness of the rest in 2-position of the 5,6-dihydro-2H-1,3-oxazines, a β-amino acid or a tricyclic C3-symmetrical heterocycle is formed.