This invention provides compounds having the structural formula: ##STR00001## wherein: R.sub.1 is an acyl or sulfonyl group, R.sub.2 is an acyl group selected from the group consisting of acyl groups derived from cycloaliphatic, aromatic or heterocyclic monocarboxylic acids, imidazolylcarbonyl and triazolylcarbonyl, and R.sub.3 is hydrogen or an amino-protecting group,a stereoisomer thereof, a solvate thereof, or a salt thereof, being useful as anti-inflammatory agents and anti-cancer agents.