The present invention provides conformationally restricted 4-substituted 2,6-dimethylfuro[2,3-d]pyrimidine compounds and pharmaceutical compositions comprising these compounds. Preferably, the compounds exhibit dual inhibition of microtubule assembly and receptor tyrosine kinases. Methods of treating cancer comprising administering a therapeutically effective amount of at least one conformationally restricted 4-substituted 2,6-dimethylfuro[2,3-d]pyrimidine compound to a patient is disclosed.