There is provided compounds of formula (I), wherein A1, A4, A4a, A5, B1, B1a, B2, B2a, B3, B3a, B4, B4a and R3 have meanings given in the description, and pharmaceutically-acceptable esters, amides, solvates or salts thereof, which compounds are useful in the treatment of diseases in which inhibition of a protein or lipid kinase (e.g. a PI3-K and/or mTOR) is desired and/or required, and particularly in the treatment of cancer or a proliferative disease.