2-Carbomethoxyphenyl isocyanate and 6-nitro-2-carbomethoxyphenyl isocy
anate were generated in situ from half-esters, and then converted into
the corresponding quinazolinediones using alpha-amino acids. This use
ful annelation process was found to be a general method for the format
ion of various chiral 3-substituted quinazolinediones.