The present invention is directed to novel compounds according to formulae ##STR00001## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are as defined herein. The invention also discloses methods of preparation, pharmaceutical compositions, and methods of disease treatment utilizing pharmaceutical compositions comprising these compounds. The compounds of this invention are novel therapeutic agents for the treatment of cancer, diabetes, metabolic diseases and skin disorders in mammalian subjects. These compounds are also useful modulators of gene expression. They exert their activity by interfering with certain cellular signal transduction cascades. The compounds of the invention are thus also useful for regulating cell differentiation and cell cycle processes that are controlled or regulated by various hormones or cytokines. The invention also discloses pharmaceutical compositions and methods of treatment of disease in mammals.