AMINATION WITH 3-ACETOXYAMINOQUINAZOLIN-4-(3H)ONES - PREPARATION OF ALPHA-AMINO-ACID ESTERS BY REACTION WITH SILYL KETENE ACETALS FOLLOWED BY N-N BOND-CLEAVAGE

Solutions of 3-acetoxyaminoquinazolinone (5) react with enol ethers and silyl ketene acetals to give alpha-aminoaldehyde alpha-aminoketone or alpha-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.