Compounds which are inhibitors of HIV protease are currently being investigated for treatment of HIV infection. Certain HIV protease inhibitors comprise a moiety which is a substituted 2,5-diamino-3,4-dihydroxyhexane. HIV protease inhibitors of particular interest are compounds of the formula 1: ##STR1## wherein R.sub.1 and R.sub.1a are independently selected from loweralkyl and R.sub.2 and R.sub.2a are independently selected from --C(O)--R.sub.4 --R.sub.5 wherein at each occurrence R.sub.4 is independently selected from O, S and --N(R.sub.6)-- wherein R.sub.6 is hydrogen or loweralkyl and at each occurrence R.sub.5 is independently selected from pyridyl or (pyridyl)alkyl; or a pharmaceutically acceptable salt, prodrug or ester thereof. Compounds of formula 1 are disclosed in European Patent Application No. EP0402646, published Dec. 19, 1990.
A preferred HIV protease inhibitor is a compound of formula 2: ##STR2## or a pharmaceutically acceptable salt, prodrug or ester thereof.