The present invention provides compounds of the following structure, wherein R.sub.1, R.sub.2, R.sub.4, R.sub.4', R.sub.6, R.sub.7, and R.sub.15 are defined above: These compounds are useful in treating neurological disorders or complications due to stroke or head injury; benign or malignant neoplastic disease, carcinomas and adenocarcinomas; proliferative disorders; and inflammatory disorders. The compounds are therefore useful as neuroprotective and neuroregenerative, anti-proliferative, and anti-inflammatory agents.