the present invention comprises analogs of the ca 1 a 2 x motif of the protein ras that is modified by farnesylation in vivo . these ca 1 a 2 x analogs inhibit the farnesylation of ras . furthermore , these ca 1 a 2 x analogues differ from those previously described as inhibitors of ras farnesyl transferase in that they have a prolyl like moiety in the a 1 position . further contained in this invention are chemotherapeutic compositions containing these farnesyl transferase inhibitors and methods for their production .