Amination with 3-acetoxyaminoquinazolin-4-(3h)ones: preparation of α-aminoacid esters by reaction with silyl ketene acetals followed by NN bond cleavage

Abstract

Solutions of 3-acetoxyaminoquinazolinone (5) react with enol ethers and silyl ketene acetals to give α-aminoaldehyde α-aminoketone or α-aminoacid derivatives. Acylation of the exocyclic nitrogen in these derivatives, as a preliminary to reductive N  N bond cleavage, could only be accomplished by indirect means. Samarium diiodide, however, effected the reduction of this N  N bond without the necessity for N -acylation. Solutions of the corresponding enantiopure 3-acetoxyaminoquinazolinone (34) brought about the diastereoselective amination of the prochiral silyl ketene acetal (15) and reductive N  N bond cleavage of the major diastereoisomer lead to enantiopure 2-phenylalanine methyl ester.