Preparation of asymmetric cyclic ureas through a monoacylated diamine intermediate

The present invention concerns an improved process for the preparation of asymmetric cyclic ureas as well as intermediates in the preparation of asymmetric cyclic ureas. In the process, a diamine of formula (I-a)is selectively monoacylated to give an asymmetric monoacylated diamine which can be converted into asymmetric intermediates. The asymmetric intermediates can be further alkylated, cyclized, and/or modified to give compounds which are useful as HIV protease inhibitors for the treatment of HIV infection. The invention allows for scalable preparation of a wide variety of asymmetrical cyclic ureas.