A series of amine cyanoboranes, amine carboxyboranes, and boron analogues of alpha-amino acids have been investigated for antineoplastic activity against the growth of Ehrlich ascites cells. Additional studies demonstrated that the boron analogues inhibited DNA and RNA synthesis at 300 microM. The suppression of DNA synthesis of Ehrlich ascites cells correlated with the reduction of DNA polymerase, 5-phosphoribosyl-1-pyrophosphate amidotransferase, and dihydrofolate reductase activities afforded by the boron compounds. These derivatives did not suppress protein synthesis, thymidylate synthetase, or thymidine monophosphate kinase activities as previously reported for some boron antineoplastic agents.